How much electricity can an 800W system generate?

An 800W system is a common reference size for plug-in solar, so it is a useful starting point for understanding what a small system can do. The honest answer is that output varies: as a rough guide, a well-placed 800W system might generate around 600–900 kWh a year in the UK. That is an indicative range, not a fixed figure — your own result depends on where you live and how the panels are placed.

Before going further, one essential point: plug-in solar cannot currently be legally sold, supplied or used in the UK. A Government consultation that could change this is open until 30 June 2026. We cover the detail on the UK legal status page.

What an 800W system might generate

For a well-placed 800W system in the UK, a yearly figure somewhere in the region of 600–900 kWh is a reasonable expectation. The lower end reflects less favourable conditions — a northern location, a less ideal orientation, or some shading — while the upper end reflects a sunny southern spot, a good south-facing angle and little or no shade. These are indicative ranges drawn from how solar output behaves in UK conditions, not a guarantee for any particular home.

Because so much depends on your specific site, the most useful number is one calculated for your address. Our calculator uses PVGIS data from the European Commission's Joint Research Centre to estimate output for your postcode, orientation and tilt, which is far more reliable than any headline figure.

What drives the output

Four factors do most of the work in deciding how much an 800W system produces:

• Location. Southern England receives more annual sunlight than northern Scotland, so the same system generates more the further south you are.
• Orientation. The direction the panels face matters a lot. South tends to be best in the UK; east and west give up a little; north gives up a great deal.
• Tilt. The angle of the panels affects how much light they capture across the year. A moderate tilt usually works well, but flat or steeply angled mounting changes the result.
• Shading. Trees, chimneys, neighbouring buildings or a balcony rail above the panels can reduce output noticeably, especially if they block the midday sun.

Orientation and indicative annual output

The table below gives a sense of how orientation alone can move the figure for an 800W system in the UK. These are illustrative ranges to show the direction and rough scale of the difference — they are not exact values, and your tilt, location and shading will shift them. For a real estimate, run your own details through the calculator.

If you are weighing up an east versus west position, our guide on east versus west-facing solar looks at how each compares for output and timing.

Generation is not the same as savings

It is tempting to multiply annual generation by your electricity price and call that your saving, but it does not work that way. Only the electricity you use while it is being generated reduces your bill. A small system is well suited to covering daytime background loads — the fridge, router and devices on standby. Anything you do not use at the time is exported, and for a self-installed plug-in system that export may currently earn nothing. Whether exported electricity is paid for at all depends on schemes such as Ofgem's Smart Export Guarantee, which is a separate matter from how much your panels generate.

This is why two homes with identical 800W systems can save very different amounts: the one that uses more electricity during daylight hours keeps more of the value.

Getting a figure you can rely on

The ranges here are a starting point, not a substitute for a proper estimate. The single most useful thing you can do is put your own postcode, orientation and tilt into the calculator, which draws on PVGIS data to produce a figure tailored to your site. Pair that with an honest look at how much electricity you use during the day, and you will have a far better sense of both generation and likely savings.