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Guide 1 of 10 · Start here5-minute read · short version 1 minute
Solar power in 5 minutes
How solar panels turn daylight into electricity for your home, where that electricity goes, and the few words you need to understand any solar quote.
Start here
The short version
- Solar panels turn daylight into electricity. They work best in bright sun, but still make some power on cloudy days.
- A box called an inverter changes it into the kind your home uses. Panels make direct current (DC). Your sockets use alternating current (AC).
- Your home uses the solar electricity first, as it is made, for things like the fridge, lights and washing machine.
- Anything you don’t use flows out to the grid. This is called exporting, and you can usually be paid for it.
- When the panels aren’t making enough, you buy from the grid as normal, for example at night. A battery can store spare solar power for later.
Layer 2
In more detail
The same five points, explained properly, with real figures.
What is in a solar system
A typical rooftop system has a handful of parts. You will see them named on any quote:
- Panels (also called modules), each made of many small cells. The Energy Saving Trust says a typical home system uses around 12 panels.
- Mounting rails and brackets that fix the panels to the roof.
- An inverter, usually one box in the loft or garage. Some systems have a small “microinverter” behind each panel instead.
- Isolator switches, so the system can be switched off safely.
- Meters. Your smart meter records the electricity you buy from and send to the grid. Many installers also fit a meter that records everything the panels make.
- A monitoring app showing what the panels are producing.
- A battery (optional) to store spare power. See Home batteries.
kW, kWh and kWp: the three words on every quote
kW (kilowatt) is power: how fast electricity is being made or used at a given moment. kWh (kilowatt hour) is energy: how much has been made or used over time. Your bill charges you per kWh, which suppliers often call a “unit”.
kWp (kilowatt peak) is the most a solar system is rated to produce under standard laboratory test conditions. On a real roof the output is usually lower. The Energy Saving Trust gives 4.5 kWp as the size of a typical home system.
How much electricity will panels make?
As a rough guide, a well-sited system in the UK may generate around 750 to 1,100 kWh a year for every kWp installed. So a 4.5 kWp system might make roughly 3,400 to 4,900 kWh a year. For comparison, Ofgem’s figure for a typical home is 2,500 kWh of electricity a year.
Where your home lands in that range depends on:
- Direction. An unshaded, south-facing roof is best. The Energy Saving Trust says east- or west-facing systems get around 15 to 20% less.
- Shade from trees, chimneys or nearby buildings. Even partial shade can cut the output noticeably.
- The angle of the roof.
- Where you live. The south of England gets more sunshine than the north of Scotland.
- The season. Panels make far more in summer than in winter, when the days are short and the sun is low.
An installer should give you a written estimate of how much your system will generate each year. Our solar generation estimator lets you check it.
Why you won’t use all of it yourself
Solar panels make most of their power in the middle of the day, but most homes use the most electricity in the morning and evening. So without a battery, a lot of solar electricity is exported at midday, and you still buy electricity in the evening.
That matters because the two are priced very differently. Under Ofgem’s price cap for 1 October to 31 December 2026, electricity costs on average 26.32p per kWh for customers paying by Direct Debit (with no VAT on domestic electricity bills from 1 October 2026 to 31 March 2027). The Energy Saving Trust says typical export payments are around 12p per kWh. So each unit you use yourself is worth roughly twice as much as a unit you export.
Ways to use more of your own solar electricity:
- Run the washing machine and dishwasher during the day, using their timers.
- Charge an electric car in the daytime when you can.
- Fit a hot water diverter, which uses spare solar power to heat your hot water tank.
- Add a home battery.
Which kind of solar?
- Rooftop panels: the usual choice for homeowners, fitted by an installer.
- Ground-mounted panels: on a frame in the garden.
- Plug-in (balcony) solar: a small kit of one or more panels that plugs into a wall socket, limited to 800 W of output. Compliant kits have been legal in England, Wales and Scotland since 27 August 2026, but not yet in Northern Ireland. See Plug-in solar explained.
- A small wired-in system: similar kit, but connected to your fuse box by an electrician, so it can be bigger than 800 W and include a battery.
Guide 2, Which type of solar suits you?, helps you choose.
Costs and lifespan
The Energy Saving Trust puts the average cost of a home system at around £7,600 for about 4.5 kWp. Panels should last 25 years or more. The inverter usually needs replacing after around 12 years, so it is worth budgeting for that.
Installing solar panels in a home currently has 0% VAT, until 31 March 2027. The 5% rate is due to return after that unless the relief is extended. See Is there VAT on solar panels?
The rules in one paragraph
Most rooftop systems on houses don’t need a planning application, but there are conditions and exceptions, for example for listed buildings, conservation areas and flats. Your installer must tell your electricity network operator about the system. To be paid for the electricity you export under the Smart Export Guarantee, the system needs an MCS (or equivalent) certificate, which means using an MCS-certified installer. Tenants and leaseholders need permission from their landlord or freeholder. Do I need permission? explains it step by step.
Key words
- kW
- Power: how fast electricity is made or used.
- kWh
- Energy: how much is made or used. One “unit” on your bill.
- kWp
- A solar system’s maximum rated output in test conditions.
- DC and AC
- Direct current (what panels and batteries use) and alternating current (what your home uses).
- Inverter
- The box that turns DC into AC.
- Export / import
- Electricity you send to the grid / electricity you buy from it.
- Network operator
- The company that runs the local power cables (sometimes called the DNO). It is not your energy supplier.
- MCS
- The Microgeneration Certification Scheme, which certifies installers and products.
Layer 3For the technically mindedWiring, test conditions, temperature, inverter sizing and grid rules
Strings, voltage and safety
Panels are usually wired in series into one or more “strings”. Their voltages add up, so a string can run at several hundred volts DC. A DC arc is harder to break than an AC one, which is why systems have DC isolators and why the DC side should only be worked on by a competent installer.
Microinverters convert to AC at each panel. Power optimisers sit behind each panel but still feed a central inverter. Both reduce the effect of one shaded panel on the rest, at extra cost and with more electronics on the roof.
What kWp actually measures
Panel ratings are measured at Standard Test Conditions: sunlight of 1,000 W per square metre, a cell temperature of 25°C and a standard light spectrum (AM1.5). Panels on a roof rarely see those conditions. Crystalline silicon panels also lose output as they heat up, typically around 0.3% to 0.4% for every degree above 25°C, so a cool, bright spring day can give higher peaks than a hot summer one.
Inverter size and “clipping”
Designs often pair an array with a slightly smaller inverter (a DC to AC ratio above 1), because panels rarely reach their full rating. In the few hours when they would, the inverter caps the output. This is called clipping, and a small amount of energy is lost. Our inverter size checker shows the trade-off for your roof.
Connecting to the grid: G98 and G99
Small type-tested systems of up to 16 amps per phase (about 3.68 kW on a normal single-phase supply) connect under Engineering Recommendation G98: the installer notifies the network operator within 28 days of commissioning. Larger systems, including generation and storage that together exceed that level, need the network operator’s agreement under G99 before installation. Systems of around 4 to 5 kWp therefore often use an inverter of about 3.6 kW to stay within G98, or an export limitation arrangement agreed with the network operator. See G98 and G99 explained.
Why solar panels switch off in a power cut
Grid-connected inverters must disconnect when the grid goes down (“loss of mains” protection), so they cannot feed power into cables that engineers may be working on. A standard system therefore gives you no power in a power cut. Some hybrid inverters and batteries offer a backup circuit, which needs the right switching and earthing arrangements, designed by the installer.
Metering and export payments
Under Ofgem’s Smart Export Guarantee, you are paid for metered exports, which in practice means a smart meter that can record export. The scheme also requires solar of up to 50 kW to be installed and certified under MCS or an equivalent scheme. See Export payments.
Standards to look for
MCS-certified installers work to the MCS solar PV installation standard (MIS 3002) and handle the network operator notification. For a G98 connection, the inverter should be listed on the Energy Networks Association’s Type Test Register.
Frequently asked questions
How long do solar panels last?
The Energy Saving Trust says solar panels should last 25 years or more, and that an inverter usually needs replacing after around 12 years.
Do solar panels work on cloudy days?
Yes, but they make less electricity. Panels respond to daylight, not heat, so they still generate under cloud, just at a lower rate than in bright sun.
Do solar panels work in a power cut?
Normally not. Grid-connected systems switch off automatically when the grid goes down, to protect engineers working on the cables. Some battery systems can provide backup power if they are designed and wired for it.
How many solar panels does a home need?
It depends on your roof and how much electricity you use. The Energy Saving Trust says a typical home system is about 4.5 kWp, which is around 12 panels.
What is the difference between kW and kWh?
kW measures power, which is how fast electricity is used or made. kWh measures energy, which is how much is used or made over time. A 2 kW heater left on for 3 hours uses 6 kWh.
Do I need a battery with solar panels?
No. A battery is optional. It lets you store spare solar electricity for the evening instead of exporting it, but it adds cost. See our guide to home batteries.
Got a question about your own home? SolarBot can explain how solar would work for you, using the rules for your part of the UK.
Ask SolarBotOfficial sources
- Energy Saving Trust: Solar panels (updated 1 October 2026)
- Ofgem: Changes to the energy price cap between 1 October and 31 December 2026
- Ofgem: Energy price cap update from 1 July 2026, revised typical consumption values (PDF)
- Ofgem: Smart Export Guarantee, guidance for generators
- MCS: notifying distribution network operators (G98 and G99)
- GOV.UK: VAT on energy-saving materials and heating equipment (Notice 708/6)
- Secondary source for the yearly output range: Kilowatts: How much solar power can I generate?
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Written 2 October 2026. General information, not legal, electrical or financial advice. Confirm current rules before you buy or connect anything.