4kW Solar Panel System Guide and Costs

A typical 4kW solar panel system will generate savings of £13,450 over 20 years and cost around £6,200. That’s a return on investment of over £7,000.

A 4kW solar panel is the largest size that qualifies for the highest Feed-in Tariff rate. Install in 2015 to lock in the high Feed-in Tariff payments over 20 years before it gets cut in 2016.

You can compare prices of leading 4kW systems by completing the form at the top of this page.

4kW solar pv systems

Being the largest system to qualify for the highest paying Feed-in Tariff band, 4kW solar systems are one of the most popular system sizes for residential installations.

A 4kW solar panel system will typically cover the energy requirements of a family home of 4 people. By installing a 4kW system you can expect to save and earn a combined total of £672.50 a year (£13,450 over 20 years) through a combination of energy bill savings and payments from the Feed-in Tariff scheme.

A typical 4kW solar system will require about 24 to 28 square meters of shade free roof space. If you have limited roof space it is possible to get a high efficiency 4kW system which would require less space, although this will be more expensive (see below for more information).

How much will I make with a 4kW system?

How will I save and earn money?

Installing solar panels allows you to save and earn money in three ways:

1. Energy Bill Savings
As you are producing free energy which you can use to power your own home, you will make significant savings on your energy bills; you can expect solar panels to reduce your electricity bills by 50% on average.

2. Generation Tariff
The Generation element of the Feed-in Tariff pays you for all the electricity you produce regardless of whether you use it to power your home or not. These payments last for 20 years and are the main reason why solar panels are so profitable.

3. Export Tariff
The Export Tariff element of the Feed-in Tariff theoretically pays you for all the electricity you don’t use which automatically goes back into the power grid. However unless your home has a smart meter, you will receive Export payments for 50% of all the electricity you generate as it’s impossible for energy companies to monitor. This means that even if you use all the electricity you generate you will still receive export payments. These payments last for 20 years.

What is the current Feed-in Tariff rate for 4kW?

The table below shows the current Feed-in Tariff rate as well as future rates confirmed by the government.

Band (kW)

Generation Tariff July to Sept 2015 (p/kWh)
Generation Tariff Oct to Dec 2015 (p/kWh)

Generation Tariff from Jan 2016

4kW or less
4 - 10kW

The Feed-in Tariff Will Be Cut In 2016

The Feed-in Tariff will be significantly cut in January 2016. The amount households can earn from the scheme will be slashed by 87 per cent. If you are considering installing a 4kW solar system, you will earn much more from the Feed-in Tariff scheme by installing in 2015 before the amount the scheme pays out gets slashed. Installing in 2015 locks you in at the higher Feed-in Tariff rate for 20 years.

How much will I earn?

The table below shows typical earnings from a 4kW system compared to other popular residential sizes:

Typical System Size

Return per Year

Return over 20 years

Profit over 20 years


The amount you will earn from a 4kW system will be significantly reduce in 2016 due to the Feed-in Tariff cut. Over 20 years you will earn around £8,143.20 less if you install in 2016 compared to households who install in 2015.

If you are considering solar panels, we strongly recommend installing in 2015 before the tariff gets slashed in January 2016. By installing in 2015 you lock in your higher tariff payments over the 20 year lifespan of the Feed-in Tariff scheme.

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How much does a 4kW solar panel system cost?

The table below shows the typical price of a 4kW system compared to other residential sizes:

Typical System Size

Approximate Roof Space

Estimated Cost (£)

Estimated Annual Output

Profit Over 20 years

8 sq m
14 sq m
21 sq m
28 sq m

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Is a 4kW system right for me?

Qualifying for the highest payout from the Feed-in Tariff, a 4kW is a popular and profitable system size for residential solar panels.

When talking to the solar installers you receive quotes from, it is always worth discussing what size would be best for your circumstances.

Generally speaking, if you have adequate roof space and use a medium or high amount of electricity a 4kW system will deliver a high return on your investment.

You might also want to consider a 5kW system if you have plenty of roof space. Even though it qualifies for a lower Feed-in Tariff band, the extra energy produced is likely to earn you more money overall. The installation costs are likely to only be a few hundred pounds more than a 4kW system so over 20 years your return on investment could be higher.


Key points to remember when installing a 4kW solar panel system:

- You will typically need 24 to 28 square meters of free roof space.

- This roof space will need to be shade free for the majority of the day to get the best results.

- 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.

- Before your installer installs the panels they are required to complete a survey of your roof structure to ensure it is suitable for solar panels. The vast majority of roofs in the UK can comfortably support the weight of solar panels, but installers are legally obliged to check.

- You will get the best results for South, South-West and South-East facing roofs. West and East facing roofs will still deliver acceptable yields.

- To qualify for the Feed-in Tariff scheme you will need to use an MCS accredited installer.

Finding the best price

It is recommended that you compare quotes from at least 3 or 4 MCS accredited installers to ensure you get the best price. Always ensure that the quote breaks down the different elements of the quote.

You can join the thousands of homeowners who have used The Eco Experts to compare prices from up to 4 local and trusted MCS accredited installers. Simply enter your postcode at the top of this page to begin. This is a completely free comparison tool which helps you find the best price.

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