Most UK homes need between 8 and 14 solar panels. A 3-bedroom home with average usage needs around 8-10 panels at 400W, a 4-5 bed home 13-16. The exact number comes down to three things: how much electricity you use, how much usable roof space you have, and whether you're adding a battery, an EV charger or a heat pump.
How to work out the number for your home
Start with your electricity bills. Your annual consumption in kilowatt-hours (kWh) is the figure that drives everything else. Pull 12 months of bills or check your smart meter app.
Each kilowatt (kW) of installed panels generates roughly 850-900 kWh per year in the UK. So divide your annual usage by 875 to get the system size you need in kW, then divide by your panel wattage to get the panel count.
A home using 3,000 kWh a year needs about a 3.5kW system. At 400W per panel, that's 9 panels.
Your installer runs this against your actual roof and shading in a few minutes, which takes the guesswork out of it.
System size by house type
| House type | Annual usage | System size | Panels (400W) | Annual output |
| 1-bed flat | ~790 kWh | 1 kW | 3 panels | ~900 kWh |
| 1-2 bed house | 1,800-2,000 kWh | 2-3.2 kW | 5-8 panels | 1,800-2,800 kWh |
| 3 bed house | 2,700-3,500 kWh | 3.2-5.2 kW | 8-13 panels | 2,800-4,500 kWh |
| 4-5 bed house | 4,100-5,000 kWh | 5.2-6.4 kW | 13-16 panels | 4,500-5,600 kWh |
| + EV charging | +2,000-3,500 kWh | +1.2-2 kW | add 3-5 panels | - |
| + Heat pump | +2,000-4,000 kWh | +1.2-2.4 kW | add 3-6 panels | - |
For a detailed breakdown of one of the most common cases, see how many panels a 3-bedroom house needs.
Does panel type change the count?
Yes. Higher-efficiency panels generate more per square metre, so you need fewer of them.
Monocrystalline panels are the standard for UK homes, at 20-25% efficiency. Polycrystalline panels are cheaper but sit at 15-18%, so they take more roof space for the same output. Thin-film is lighter and more flexible at 10-13% efficiency, which suits some flat-roof and commercial jobs but rarely a domestic pitched roof.
If your roof space is tight, fewer high-wattage panels (440W+ at 22% efficiency) beat more low-wattage ones. A 9-panel 440W array can match a 12-panel 350W array. A good installer recommends on this basis rather than just adding panels to hit a number.
How much roof space you need
A typical domestic system needs from about 13m² of usable roof for a small array up to 28m² for a larger one. Each panel is roughly 1.7m x 1m, and that barely changes with wattage, so a 400W and a 450W panel take almost identical space.
The smaller your roof, the more it pays to choose higher-wattage panels to get the most from the area you have.
What affects how much each panel generates
Orientation. South-facing roofs give the best annual output. East or west-facing roofs generate roughly 15-20% less, so you may need an extra panel or two to hit the same total. North-facing isn't worth fitting. There's more detail in our guide to the best direction for solar panels and the optimum panel angle.
Shading. Trees, chimneys and neighbouring buildings cut output during the hours they cast shadows, and shade on one panel in a string can drag down the whole array. Panel-level optimisers or microinverters recover most of that loss.
Location. UK homes get around 1,100-1,300 peak sun hours a year. Southern England generates more than Scotland for the same system.
What about fewer than 6 panels?
Six well-oriented panels generate around 2,000-2,400 kWh a year, enough to cover most of a two-person household's daytime electricity. Below four panels, the output rarely justifies the fixed costs: survey, scaffolding, inverter and labour are much the same regardless of panel count. There's no regulatory minimum, it's purely a question of whether the output earns its keep.
Adding a battery, EV charger or heat pump
A battery stores daytime generation for evening use, so if you're adding one, size the panels slightly larger than your immediate needs to fill it. A 5kW system with a 10kWh battery is a common pairing for a 3-bed home.
An EV charger adds 2,000-3,500 kWh a year if you charge at home, and a heat pump 2,000-4,000 kWh. Plan for these at the outset and size the system from the start, retrofitting more panels later is possible but costs more than doing it in one visit.
FAQ
How many panels to run a house off-grid? Most UK off-grid setups need 16-20 panels plus a large battery bank to cover nights and cloudy spells. It's a niche choice. Most homeowners stay grid-connected and use the Smart Export Guarantee to sell their surplus.
How many panels for 500 kWh a month? At 6,000 kWh a year, around a 7kW system, roughly 17-18 panels at 400W.
What size system for a 4-bedroom house? Typically 5-6kW, around 13-16 panels, depending on usage and roof.
Can I add more panels later? Yes, within limits. Your inverter has a maximum input rating and your DNO connection may cap system size, so flag any expansion plans to your installer at the outset.
Get the right system for your home
The quickest way to an accurate answer is a proper assessment of your roof, orientation, shading and bills. You can also try our solar panel cost calculator for an instant estimate, or read up on what solar panels cost in the UK.
CRG Direct offers free, no-obligation quotes across Hampshire, Guildford and the South Coast. MCS-certified engineers, HIES accredited.
Contact us for a free site survey and quote. We'll respond within one working day.
Sources
- Ofgem, Smart Export Guarantee (SEG): official scheme page.
- Energy Saving Trust, solar PV sizing and output guidance: energysavingtrust.org.uk.