​What Does Solar PV Mean?

 

Solar PV means solar photovoltaic.

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Photovoltaic technology converts light into electrical energy.

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A solar panel contains multiple photovoltaic cells. When daylight reaches these cells, electrical energy is produced.

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Several cells make up a solar module, commonly referred to simply as a solar panel.

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Several solar panels connected together create a solar array.

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That array then forms part of the complete photovoltaic system installed on the property.

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In simple terms:

sunlight → photovoltaic panels → electricity → inverter → your property.

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Solar PV and Solar Panels – What's the Difference?

 

The terms are often used interchangeably.

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When people talk about solar panels for generating electricity, they are normally talking about solar PV panels.

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Technically, however, "solar panel" can describe different solar technologies.

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Solar photovoltaic panels produce electricity.

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Solar thermal panels are designed primarily to capture heat, usually for producing hot water.

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Most modern residential and commercial solar installations are photovoltaic systems.

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What Are Photovoltaic Panels?

 

Photovoltaic panels contain semiconductor materials that produce an electrical current when exposed to light.

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Individual photovoltaic cells are connected together within a protective panel.

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A typical solar module includes:

protective glass, photovoltaic cells, electrical connections, backing materials and an outer frame.

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The front surface is designed to allow as much useful sunlight as possible to reach the photovoltaic cells below.

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This is also why modern panels are generally designed to minimise reflection rather than behave like mirrors.

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How Do PV Panels Generate Electricity?

 

When light reaches a photovoltaic cell, energy within the light causes electrons inside the semiconductor material to move.

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This movement creates an electrical current.

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The electricity produced by the PV panels is direct current, usually abbreviated to DC.

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Most homes and businesses operate using alternating current, or AC.

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The solar electricity therefore needs to pass through an inverter before it can normally be used by the property.

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What Is a Solar PV System?

 

A complete solar PV system contains considerably more than the panels visible on the roof.

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A typical system can include:

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• photovoltaic panels

• roof mounting equipment

• DC cabling

• inverter

• AC electrical connections

• isolators and protective equipment

• generation monitoring

• smart meter integration.

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Depending upon the installation, it may also include:

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• battery storage

• EV charging

• solar optimisation equipment

• energy-management controls.

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The individual components need to work together as one properly designed electrical system.

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The Solar Panels

 

The solar panels are the most visible part of the installation.

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Their job is to collect daylight and convert it into DC electricity.

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Panels are normally installed where they will receive good solar exposure with limited shading.

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For a house, this will most commonly be the roof.

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For commercial and agricultural properties, panels might be installed on large warehouse, office or barn roofs.

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Ground-mounted systems are another possibility where suitable land is available.

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What Is a Solar Module?

 

A solar module is essentially an individual manufactured photovoltaic panel.

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The term is common within technical specifications and solar-industry literature.

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Several modules are connected electrically to form strings, and these are combined to create the required solar array.

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For most homeowners, the terms solar module, PV panel and solar panel can be treated as referring to essentially the same physical component.

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What Does the Solar Inverter Do?

 

The inverter is one of the most important components of a photovoltaic system.

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Solar panels produce DC electricity.

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The inverter converts this into AC electricity suitable for use within the property.

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It also monitors and manages the operation of the solar array.

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A system may use a single inverter serving several panels or a different arrangement depending upon the design.

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The location, specification and capacity of the inverter should be considered carefully when designing the installation.

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What Happens to the Electricity?

 

Once converted into usable AC electricity, solar power can be used within the property.

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If the solar panels are generating 3kW and the building is consuming 3kW at that moment, the solar system could theoretically meet that demand without requiring additional electricity from the grid, allowing for normal system considerations and losses.

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If the property requires more electricity than the panels are producing, the difference is supplied from the grid.

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If the panels produce more than the property is using, the surplus has to go somewhere.

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It can potentially be:

exported to the grid, stored in a battery or directed towards another useful electrical load.

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That last point is becoming increasingly important.

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Using Solar Electricity in the Home

 

Solar electricity does not need special appliances.

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Once properly connected to the property's electrical system, it can contribute towards the electricity being used by ordinary equipment throughout the house.

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That might include:

lighting, televisions, computers, washing machines, dishwashers, refrigerators and cooking equipment.

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It can also contribute towards larger electrical loads such as:

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EV chargers, heat pumps and air-conditioning systems.

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The more solar electricity that can be used directly within the property, the less electricity normally needs to be purchased from the grid.

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Solar PV and Battery Storage

 

A battery allows surplus solar electricity to be stored rather than immediately exported.

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Imagine a solar system generating strongly around midday while relatively little electricity is being used in the house.

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Without a battery, much of that surplus may leave the property through the grid.

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With battery storage, some of it can be retained.

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Later in the evening, when the panels are producing little or no electricity, the house can draw electricity from the battery.

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The basic energy flow becomes:

solar panels → home → battery → grid.

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The precise priorities can be controlled by the system.

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Solar PV and Electric Cars

 

An electric vehicle can provide another major use for solar-generated electricity.

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If an EV is connected while the panels are producing electricity, some of the energy from the roof can contribute directly towards charging the vehicle.

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Smart EV chargers can help coordinate charging with available solar generation.

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This creates a very attractive concept for homeowners:

generate electricity on your roof and put some of it directly into your car.

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The amount of solar charging possible will depend upon the size of the photovoltaic system, weather, household consumption and when the vehicle is parked at home.

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Solar PV and Air Conditioning

 

Solar PV can also work extremely well with air conditioning.

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The relationship is particularly logical because the strongest requirement for cooling often occurs during bright, warm summer weather — exactly when solar panels are capable of substantial generation.

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Instead of exporting excess solar electricity during a hot afternoon, some of that electricity can potentially be used to cool the house.

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Modern air-conditioning units are commonly based on heat-pump technology and can also provide heating.

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This creates the possibility of integrating solar generation with year-round heating and cooling.

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Solar PV and Heat Pumps

 

Solar panels can also contribute towards the electricity required by an air-source or ground-source heat pump.

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Solar output is lower during winter, precisely when heating demand is generally greatest, so solar should not be presented as independently powering a heat pump throughout winter.

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However, the technologies can still complement one another.

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During brighter periods, solar generation reduces the amount of electricity that the heat pump needs to draw from the grid.

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Battery storage and smart tariffs can add further flexibility.

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The Integrated Home Energy System

 

Increasingly, solar PV should not be considered as an isolated product.

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A modern property could combine:

solar PV + battery storage + EV charging + air conditioning/heat pumps + smart controls.

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Solar generates electricity when daylight is available.

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The house consumes some directly.

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A battery stores some for later.

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An electric vehicle provides another substantial demand.

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Air conditioning can make productive use of strong summer generation.

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Smart controls coordinate the movement of energy between them.

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This is much closer to a complete home energy system than simply putting a few solar panels on a roof.

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Rooftop Solar Panels

 

Rooftop solar panels are the most common form of domestic photovoltaic installation.

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Using the roof avoids taking up additional garden or land area and positions the panels where they can often receive relatively unobstructed daylight.

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Panels can be installed on many different roof types including:

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• tiled pitched roofs

• slate roofs

• standing-seam metal roofs

• profiled roofs

• flat roofs.

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Each requires an appropriate mounting system.

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Solar Panels on Pitched Roofs

 

On a conventional pitched roof, mounting brackets are normally fixed back to the roof structure.

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Rails are attached to these brackets and the solar panels are secured to the rails.

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The roofing is carefully detailed around the brackets so the roof remains weatherproof.

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Solar-panel layout needs to consider:

chimneys, rooflights, dormers, shading and available roof area.

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A well-designed array should also look considered rather than appearing to have been fitted wherever individual panels could be squeezed in.

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Solar Panels on Flat Roofs

 

Flat roofs require a different approach.

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Panels can be mounted onto specialist frames that provide an appropriate inclination.

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The arrangement needs to take account of:

wind loading, shading between rows, roof drainage, rooflights and maintenance access.

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Some systems use ballast to secure the mounting system without penetrating the waterproof roof covering.

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Where ballast is used, its additional weight needs to be considered structurally.

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Which Direction Should Solar Panels Face?

 

In the UK, south-facing panels can provide excellent annual generation.

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But that does not mean solar panels must face south.

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East- and west-facing installations can also work very effectively.

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An east-facing system produces more electricity earlier in the day.

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A west-facing system produces more later in the afternoon.

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This can sometimes correspond better with the way electricity is actually consumed.

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For example, a household using significant electricity during the late afternoon and early evening may find west-facing generation useful.

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Does Solar Panel Angle Matter?

 

Yes.

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The inclination of a solar panel affects how sunlight reaches its surface throughout the year.

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However, there is not one single perfect panel angle that must be achieved on every building.

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Roof-mounted installations will frequently follow the existing roof pitch.

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Flat-roof mounting systems allow greater control over panel inclination.

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The designer needs to balance annual generation with roof arrangement, wind loading, shading and the physical constraints of the property.

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What About Shading?

 

Shading can reduce photovoltaic output.

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Potential sources include:

trees, chimneys, neighbouring buildings, dormers and other roof structures.

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The effect depends upon where the shading occurs and when.

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A chimney casting a small shadow early in the morning is different from a large tree shading the solar array through the middle of every day.

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Modern design software can model these effects when assessing a proposed solar installation.

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Do Solar Panels Work on Cloudy Days?

 

Yes.

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Photovoltaic panels respond to daylight rather than requiring uninterrupted direct sunshine.

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Generation will generally be lower under heavy cloud than during clear sunny conditions, but the panels can continue producing electricity.

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This is important in the UK, where solar systems operate throughout the year despite variable weather.

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The relevant measure is therefore the expected annual generation, not simply output on an exceptionally sunny day.

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Do Solar Panels Work in Winter?

 

Yes, although they generally produce considerably less electricity during winter.

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Winter days are shorter and the sun is lower in the sky.

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Weather conditions can also reduce available solar radiation.

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This seasonal variation needs to be understood when planning a photovoltaic system.

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A solar installation may generate substantial surplus electricity during parts of the summer while needing significant grid electricity during winter.

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Battery storage can shift electricity between different parts of a day, but a normal domestic battery cannot store summer electricity for use several months later.

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How Efficient Are Solar Panels?

 

Solar-panel efficiency describes the proportion of incoming solar energy that the panel can convert into electricity.

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A more efficient panel can produce more power from the same physical roof area.

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Efficiency therefore becomes particularly important where roof space is limited.

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If you have a very large warehouse roof, slightly lower panel efficiency may matter less because plenty of space is available.

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If you have a small domestic roof, fitting the most efficient solar panels available within the project budget could allow greater generating capacity from the limited area.

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Most Efficient Solar Panels

 

The most efficient solar panels are not automatically the best panels for every installation.

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Efficiency is only one factor.

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A solar installer should also consider:

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panel output, physical dimensions, warranty, degradation, manufacturer support, appearance and cost.

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A slightly less efficient panel could potentially provide better overall value if its specification, warranty and price are more appropriate.

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The correct comparison is therefore between the complete systems rather than one efficiency percentage in isolation.

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Solar Panel Output

 

Individual solar panels are normally given a rated power output.

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Higher-output modules can provide greater generating capacity from a given number of panels.

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However, quoted panel output does not mean the panel will continuously produce that amount of electricity.

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Actual generation continually changes according to:

available sunlight, panel temperature, orientation, shading and time of day.

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The important figure for the property owner is usually the estimated annual generation of the complete solar array.

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kW and kWh Explained

 

Two units regularly appear in solar discussions.

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kW – kilowatts describes power.

kWh – kilowatt-hours describes energy used or generated over time.

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A solar PV system might have a particular generating capacity measured in kW.

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During the year it will produce a quantity of electricity measured in kWh.

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Electricity bills also generally show consumption in kWh.

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Understanding the difference makes solar quotations much easier to compare.

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What Is kWp?

 

Solar installations are often described using kWp, meaning kilowatt peak.

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This represents the rated peak output of the photovoltaic array under standard test conditions.

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For example, several solar modules together might create a particular kWp system.

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The actual output at any individual moment will vary.

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kWp therefore describes the nominal capacity of the system rather than the electricity it produces every hour.

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How Many PV Panels Do I Need?

 

There is no universal answer.

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The appropriate number depends upon:

roof area, household electricity use, panel output, roof orientation, shading, battery storage and future electrical demand.

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Future demand is becoming increasingly important.

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A homeowner who currently uses relatively little electricity could have very different requirements after installing:

an electric vehicle, air conditioning or a heat pump.

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It can therefore make sense to consider where the household is heading rather than designing purely around its electricity consumption today.

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Should I Fill the Entire Roof With Solar Panels?

 

Not necessarily — although sometimes it can make sense.

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Traditionally, solar systems were often designed primarily around current household consumption.

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But electricity use is changing.

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Homes are gradually replacing fossil-fuel energy with electricity through:

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EV charging, heat pumps, induction cooking and cooling.

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Battery storage also provides another way of using surplus generation.

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If the property has an excellent solar roof, installing additional capacity may therefore be worth considering even if current consumption is relatively modest.

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The economics should be assessed for the individual property.

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How Is Solar Generation Calculated?

 

Solar installers use specialist software to estimate system performance.

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The calculation can consider:

property location, roof orientation, panel angle, system size and shading.

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More sophisticated modelling can also incorporate detailed three-dimensional surroundings and system losses.

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The resulting estimate provides an indication of how much electricity the proposed system might generate during a typical year.

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Generation estimates should always be treated as predictions rather than guarantees because actual weather varies from year to year.

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Solar PV Design Software

 

Professional installers can use specialist PV design software to model photovoltaic systems.

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This can help assess panel layouts, orientation, shading and anticipated generation.

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For larger installations, modelling becomes particularly useful because small design decisions multiplied across hundreds of panels can have a meaningful effect upon overall performance.

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Software should support good professional judgement rather than replace a proper survey of the building.

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What Is a Solar Optimiser?

 

Solar optimisers are electronic devices that can be fitted to individual panels in certain photovoltaic system designs.

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They allow panel performance to be managed more independently.

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This can be useful on roofs experiencing variable shading or where panels face different directions.

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They may also provide panel-level monitoring.

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However, optimisers are not automatically necessary on every solar installation.

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The installer should determine whether they provide a genuine benefit for the particular roof.

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Microinverters

 

A conventional solar system may connect several panels to a central inverter.

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An alternative arrangement uses microinverters, generally associated with individual panels.

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This can allow each panel to operate more independently.

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Microinverters can be attractive for complicated roofs with multiple orientations or shading conditions.

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As with optimisers, the choice should be based upon the building and system design rather than assuming one technology is universally superior.

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Solar Panel Monitoring

 

Modern photovoltaic systems generally include monitoring.

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This allows homeowners or businesses to see how much electricity the panels are generating.

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More comprehensive energy monitoring can show:

solar generation, property consumption, battery charging, battery discharging, grid imports and grid exports.

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This information is extremely useful.

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It allows occupants to adjust when they use electricity and potentially increase the amount of solar power consumed directly within the property.

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Using Appliances When Solar Is Generating

 

A household can potentially improve solar self-consumption by moving flexible electrical loads into daylight hours.

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For example, washing machines and dishwashers can be programmed to operate while solar generation is available.

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EV charging can also be scheduled around solar production.

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Battery systems and smart controls can increasingly automate many of these decisions.

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The objective is not necessarily to change your entire lifestyle around the solar panels.

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Technology can increasingly manage the electricity intelligently in the background.

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Exporting Solar Electricity

 

When the photovoltaic system generates more electricity than the property can use or store, surplus electricity can be exported into the grid where the installation and electricity arrangements permit.

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Exported electricity may attract payment under an appropriate electricity-export tariff.

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The financial value of export can differ from the value obtained by using the electricity directly.

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This is one reason why good system design considers not simply how much electricity is generated but where that electricity goes.

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Solar Self-Consumption

 

Solar self-consumption means using the electricity generated by the panels within the property rather than exporting it.

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Imagine a system generates 4,000kWh during a year.

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If 2,500kWh is used within the property, the self-consumed proportion is 2,500kWh.

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Increasing self-consumption can potentially be achieved through:

battery storage, EV charging, daytime appliance use and other controllable electrical loads.

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As homes become increasingly electrified, opportunities for using solar electricity directly can increase.

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Solar PV for Businesses

 

Commercial properties can provide particularly strong opportunities for solar PV.

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Offices, warehouses, factories, farms and schools often combine large roof areas with significant daytime electricity consumption.

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This means electricity can be produced and consumed in the same building at the same time.

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Commercial systems can range from modest rooftop arrays to installations containing thousands of panels.

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Larger systems may also incorporate commercial battery storage and substantial EV-charging infrastructure.

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Solar PV for New Extensions

 

An extension or major refurbishment can be one of the best times to consider solar.

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The roof is already being designed.

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Electrical work is already taking place.

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Scaffolding may already be required.

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Cable routes can be planned before ceilings and walls are finished.

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An inverter and battery position can be incorporated into the design rather than added later.

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This makes solar particularly relevant when homeowners are already making substantial changes to a property.

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Designing a New Roof for Solar

 

Where a completely new roof is being created, solar should ideally be considered before its orientation, rooflights and other details are finalised.

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The designer may be able to create a cleaner and more efficient panel layout by coordinating solar with the architectural design.

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Even decisions about where rooflights are positioned can affect how many photovoltaic modules will eventually fit.

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The same applies to dormers, chimneys and ventilation terminals.

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Thinking about solar early can therefore materially improve the final installation.

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Integrated Solar Panels

 

Not all photovoltaic panels need to sit above the roof covering.

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Roof-integrated solar systems can replace part of the conventional roof finish.

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This can produce a cleaner appearance, particularly on new roofs and extensions.

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The cost, weatherproofing arrangement, ventilation and system specification need to be considered carefully.

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For some architectural projects, however, integrated solar can provide an attractive alternative to conventional surface-mounted panels.

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Planning Permission for Solar PV

 

Many residential rooftop solar installations can be undertaken without a conventional planning application, subject to the relevant limitations and conditions.

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However, not every property is the same.

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Planning considerations can become more important for:

listed buildings, conservation areas, prominent installations, unusual roof arrangements and ground-mounted systems.

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Commercial installations have their own planning considerations.

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The planning position should therefore be checked before installation where there is any doubt.

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Is My Roof Strong Enough for Solar Panels?

 

The existing roof needs to support the solar installation safely.

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Panels add additional permanent load, while wind forces can create additional stresses on mounting systems and roof structures.

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Most straightforward modern roofs may accommodate conventional installations, but assumptions should not be made.

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Older roofs, unusual structures, lightweight commercial roofs and systems involving substantial ballast may require structural assessment.

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The condition of the roof should also be considered.

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Should I Replace My Roof Before Installing Solar?

 

If the roof is nearing the end of its useful life, potentially yes.

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A solar installation may remain in place for decades.

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Installing panels onto a roof that needs major replacement shortly afterwards could mean paying to remove and reinstall the entire array.

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This is particularly relevant for older flat roofs and commercial buildings.

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Coordinating roof work and solar installation can often be much more sensible.

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Solar PV Maintenance

 

Photovoltaic systems generally have relatively modest maintenance requirements.

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There are few moving parts.

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However, the system should still be monitored and periodically inspected.

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Potential maintenance considerations include:

panel condition, mounting equipment, electrical connections, inverter performance and monitoring equipment.

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Panels may occasionally benefit from cleaning where significant dirt or deposits accumulate.

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How Long Do Solar Panels Last?

 

Solar panels are designed for long-term operation.

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Their output normally declines gradually over time rather than suddenly stopping after a particular number of years.

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Panel warranties commonly distinguish between:

the physical product warranty and performance-related guarantees.

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Other components may have different expected working lives.

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The inverter, for example, should be considered separately from the panels when evaluating the complete system.

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Solar Panel Warranties

 

When comparing systems, look beyond the headline length of a warranty.

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Consider:

who provides it, what it actually covers and what happens if a component fails.

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Panel, inverter, battery and workmanship warranties may all be separate.

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For a system expected to operate for decades, manufacturer strength and installer support can be just as important as buying equipment with impressive specifications.

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Choosing a Solar Panel Installer

 

The quality of the solar panel installer can have a major effect on the performance and durability of the system.

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Solar installation combines several disciplines:

roofing, electrical work, system design and energy analysis.

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For more complicated installations it may also involve:

structural engineering, planning and battery-system integration.

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A good installer should therefore assess the property before recommending equipment.

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Be cautious of quotations apparently based only on the number of panels that can physically fit on an online image of the roof.

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Comparing Solar PV Quotations

 

Solar quotations can initially appear difficult to compare because different installers may recommend different equipment and system sizes.

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Useful information includes:

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• number of panels

• individual panel output

• total system capacity

• estimated annual generation

• inverter specification

• battery capacity where applicable

• predicted export

• warranties

• monitoring

• installation and scaffolding costs.

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The cheapest system is not automatically the best value.

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The quality of the design and installation will influence the property for many years.

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Is Solar PV Worth It?

 

For many properties, solar PV can be an attractive long-term improvement.

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But the answer depends upon more than roof orientation.

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The financial and practical case is affected by:

installation cost, electricity consumption, available roof space, shading, electricity tariffs and how much solar generation can be used directly.

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Future electricity requirements should also be considered.

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A homeowner intending to install an electric vehicle, air conditioning, battery storage or electric heating may eventually use considerably more electricity than they do today.

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Solar PV Is Becoming Part of the House

 

Perhaps the most important change is that photovoltaic panels should no longer necessarily be viewed as an isolated environmental accessory.

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Electricity is becoming increasingly central to how a modern house operates.

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The house may generate electricity through solar PV.

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It can store electricity in a battery.

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It can use electricity to charge the car.

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It can use efficient electrical equipment to cool the house in summer and contribute towards heating in winter.

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Smart controls can coordinate these systems automatically.

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Solar therefore becomes the generating component at the centre of a much broader home-energy strategy.

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Planning a Solar PV System?

 

A good photovoltaic system starts with the property rather than the product catalogue.

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Roof orientation, available area, shading, structural condition and existing electricity use should all be assessed.

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Just as importantly, think about what may change over the next few years.

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Are you likely to buy an electric car?

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Would you like air conditioning?

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Are you considering battery storage?

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Could heating become more electrically powered?

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Are you already extending or refurbishing the property?

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Answering those questions can significantly change the appropriate size and design of the solar installation.

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APN Solar can help homeowners and businesses connect with experienced solar panel installers who can assess the property, explain the available options and provide quotations for a properly designed solar PV system, including battery storage and associated energy technologies.

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