How Many Solar Panels Do I Need? A UK Home Guide

◆How many solar panels do I need?

Most UK homes end up with between 8 and 18 panels. The right number depends on three things. How much electricity you use. How much roof you have. How much of your bill you want to cover.

This guide walks you through the sums. You can do them roughly at the kitchen table before anyone visits.

◆The panel size everything here is based on

We fit 450–500W panels on homes. Every count, output and area on this page is worked out from that range. Commercial roofs take larger panels, so the figures there are different.

That matters, because a lot of solar advice online is still written around 400W panels. Using an old panel size makes every panel count too high by roughly a sixth.

The three panels on our published projects sit inside that range. They are the Jinko Solar JKM470N-60HL4 at 470W, the JA Solar JAM54D41-460/LR at 460W and the Aiko Energy AIKO-A475-MCE54Mb at 475W. Which one suits your roof is decided at the survey.

◆How much electricity does your home use?

Start with your own bill, not an average. Your annual usage in kWh is on it, and it is the single most useful number you have.

If you cannot find it, we group homes into three bands. These are the same bands our quote system uses, so the figure in your quote will match.

Band	Annual electricity use	Typically
Low	About 2,000 kWh	A flat or a small home, one or two people
Medium	About 3,500 kWh	A three bedroom house
High	About 5,000 kWh or more	A larger house, or an electric car

An electric car, a heat pump or electric heating pushes you well up this table. It also makes solar more useful, because you have somewhere to put the power.

◆How much does a panel generate?

This depends on which way your roof faces and how steep it is. The European Commission's PVGIS tool models it for any location.

For Eastbourne, at a 35 degree pitch and with 14% system losses, PVGIS gives these figures for every 1 kWp of panels:

Roof direction	Modelled output per 1 kWp	Share of a south facing roof
South	1,156 kWh a year	100%
West	915 kWh a year	79%
East	879 kWh a year	76%

On a south facing roof, that works out at roughly 520 to 580 kWh a year for a single 450–500W panel.

Two things to hold on to. These are model figures for a clear roof with nothing shading it. And an east or west roof still does about three quarters of what a south roof does, which is usually well worth having.

◆How many panels for each system size?

System size is measured in kWp, which is the rated output of all the panels added together. Here is what each size takes at 450–500W per panel.

System size	Panels at 450–500W	Modelled output, south facing
3 kWp	6 to 7	About 3,500 kWh a year
4 kWp	8 to 9	About 4,600 kWh a year
5 kWp	10 to 12	About 5,800 kWh a year
6 kWp	12 to 14	About 6,900 kWh a year
8 kWp	16 to 18	About 9,200 kWh a year
10 kWp	20 to 23	About 11,600 kWh a year

The output column is the PVGIS figure for a south facing roof at 35 degrees. Turn the roof east or west and it drops to about three quarters of that. Add shade and it drops again.

◆How much roof space do you need?

Allow about two square metres per panel. The Aiko Neostar 3S+54 datasheet gives a module size of 1762mm by 1134mm, which is just under two square metres. The larger 60 cell panels we also fit take a little more.

System size	Panels	Panel area
4 kWp	8 to 9	About 16 to 18 m²
6 kWp	12 to 14	About 24 to 28 m²
8 kWp	16 to 18	About 32 to 36 m²

Your roof needs to be bigger than the panel area. Panels are kept clear of the edges, the ridge and the gutter. Vents, dormers and soil pipes all take usable space out of the middle.

So measure your roof, then expect a survey to come back with a slightly smaller usable area than you hoped. If the south face is small, panels can go on two faces instead.

◆Do you need permission from the network?

Your Distribution Network Operator has to know about the system either way. The threshold is 3.68kW per phase, and it decides whether they are told before or after.

That threshold is not the panels' kWp rating. It is the connected generation capacity per phase, which on an inverter system is normally the inverter's AC output. So a 4 kWp array on a 3.68kW inverter still sits inside the lower route.

• Up to 3.68kW per phase. This is the G98 connect and notify route. The installer fits the system, then tells the network within 28 days of commissioning. It applies to type tested equipment at a single premises with no other generation counted in.
• Above 3.68kW per phase. This is the G99 route. The network wants the technical details first and has to approve the design before the system goes in.

Plenty of homes land in the second group once the inverter is sized. We handle either route as part of the job, and it is included in the price.

◆Should you fit more panels than you need today?

Often yes, if the roof has the room and the budget allows.

• Adding panels later means hiring scaffolding again, so it costs more than doing it once.
• Spare generation is exported, and export pays you rather than nothing.
• Household electricity use tends to rise, especially once a car or a heat pump arrives.
• A bigger array makes a battery more useful, because there is more surplus to store.

There is a limit, though. Panels on a roof face that is heavily shaded, or pointing the wrong way, may not earn their place. We would rather tell you that than sell you them.

◆What about a battery?

A battery does not change how many panels you need. It changes what those panels are worth to you.

Without one, the power you make at midday and do not use goes to the grid. Export pays 4p–15p per kWh, set by your supplier. In the evening you buy that electricity back. If you are on a standard variable tariff the price cap sets your unit rate. That is 26.11p per kWh from 1 July to 30 September 2026, rising to 26.32p per kWh from 1 October. Fixed and multi-rate tariffs differ. A battery keeps that gap for you instead.

◆What will it cost?

A 4kW system, which is 8 or 9 panels, costs £6,000–£8,000 fitted. A typical home then saves £700–£1,200 a year on bills and export payments together. Our guide to solar panel costs breaks that down properly.

◆Getting the size right

A free survey is the only way to be sure. We look at four things:

• The direction your roof faces, its pitch, and how much of it is usable.
• What shades it, from trees, chimneys and neighbouring buildings.
• Your bills and when in the day you use power.
• What is coming next, such as a car, a heat pump or an extension.

Send us an enquiry and we will call you back within 1 working day.

◆Common Questions

How many solar panels does an average UK home need?

Most homes end up with somewhere between 8 and 18 panels. We fit 450–500W panels on houses, so a 4kW system is 8 or 9 of them and a 6kW system is 12 to 14. The right number comes from your bills and your roof, not from an average.

How much does one solar panel generate in a year?

It depends which way the roof faces. PVGIS models a 1 kWp array in Eastbourne at a 35 degree pitch. Facing south it gives 1,156 kWh a year, west 915 kWh and east 879 kWh. That puts a single panel at roughly 520 to 580 kWh facing south.

How much roof space do I need for solar panels?

Allow about two square metres per panel, plus clear space around the edges of the array. So a 4kW system needs roughly 16 to 18 square metres of panel, on a bigger roof than that. A survey settles it, because usable area is not the same as roof area.

Do I need permission from the network to fit solar panels?

Your Distribution Network Operator has to know either way. Up to 3.68kW per phase your installer can connect the system and notify them within 28 days. Above that, the network has to approve the design first. We handle both, and it is included in the price.

Should I fit more panels than I need right now?

Often yes, if the roof has room. Adding panels later means scaffolding again, so it costs more than fitting them the first time. Your electricity use is also more likely to rise than fall, especially if a car or a heat pump is coming.

Do I need a battery as well?

No, but it changes what your panels are worth to you. A battery keeps the midday power for the evening instead of exporting it. Export pays 4p–15p per kWh, and you buy electricity back at more than that. On a standard variable tariff the price cap sets that buy back rate; fixed and multi-rate tariffs differ.

◆Next steps

Request a free survey and system recommendation →

Estimate your system size with our solar calculator →

How our solar installation service works →