4kW Solar Panel Systems

A 4kW solar panel system can earn and save you up to £877 a year and cost from £5,000 if installed by a MCS certified supplier.

A 4kW solar panel is the largest size you can install under the domestic Feed-in tariff rate.

You can complete the form above to receive quotes from installers in your area.

a diagram showing how solar PV panels work

4kW solar pv systems

Solar panel systems (also known as solar photovoltaics or solar PV) convert the sun’s energy into electricity.

This can either be stored in batteries, or feed straight into your mains supply depending on whether you get an off-grid or grid tied system.

A 4kW system is one of the most popular system sizes for residential installations as it is the the largest size applicable for the highest Feed-in Tariff band for homeowners

Feed-in tariffs

The Feed-in tariff is a government incentive to encourage people to install solar panels. You will earn 12.92p for each kWh of electricity you generate and use.

You will also earn 4.85p per kWH for the energy you generate, but don't use. This gets sold back to the grid.

There rates may vary depending on the system size and when it was installed and you will only earn the FiT if your installer was MCS accredited.

On top of this your energy bills will also become much lower as you power your house with free electricity.

UPDATE: The government is going to review the future of the FiT at the start of 2016 so if you are thinking about installing you will want to install sooner rather than later so you don't miss out on the 20 year long payments. The government have confirmed that anyone who installs before the review in 2016 will still be guaranteed the FiT payments for 20 years.

How much money can I save or earn?

The amount of money a 4kW solar PV system will save or earn you may vary depending on how much sun the panel absorbs and how efficiently you use your energy.

The amount of sun your panel receives can be affected by the direction of the solar panels, the geographical location and whether the roof is shady or not.

Assuming only 50% of the energy generated is used and the 4kW solar PV system is in London, then the savings you make on your energy bill, and revenue generated from the FiT could amount to around £800 a year.

The exact amount you end up with will vary and it always helps to make as many energy saving measures as you can. Never leaving appliances in standby mode and take showers instead of baths. Remember, it is always cheaper to save energy than generate it, even using solar PV panels.

Approximate Roof Space

Typical System Size
Estimated Cost (£)

Estimated Annual Output

CO2 saved over 25 years (tonnes

Estimated First Year Return
Profit Over 20 years
8 sq m
14 sq m
21 sq m
28 sq m

*Calculations based on roof with 35 degree angle and South facing with little or no shade.

Use our solar calculator to see how much you will save save and earn.

4kW Solar system costs

A typical 4kW solar system will cost about £7,000 installed. However, the price will vary between suppliers and depending on which solar panel brand you chose. Only use MCS accredited installers or you will not be eligible for the Feed-in tariff.

Deciding to invest in solar energy can be a big decision so it's important you are completely happy. Make sure you do plenty of research and use a legitimate solar energy comparison and information site like this one.


Most household roofs will be suitable for a 4kW solar panel, though you will need 21m2 of roof space.

Unless your roof is particularly shadowy or completely north-facing, you should be fine. If you live in a listed building or conservation area you may need planning permission.

While south-facing roofs are ideal, east and west-facing rooftops only produce 15% less electricity.

You will also need a small amount of space (normally in the attic) for your inverter. This converts the sun’s light into the energy you will use.

Solar panels can also be installed so they fit around skylights and other features.