If you’re researching solar for the first time, it is understandable that you might be wondering
“How many solar panels do I need?”
The honest answer is – it depends on your electricity usage, roof space, budget and generation goals. This guide explains exactly how solar panel system sizing works, using real UK data, so you can make an informed decision.
Start With Your Annual Electricity Usage
The most accurate way to size a solar PV system is by reviewing your annual electricity consumption (kWh). You can find this on your electricity bill or smart meter account.
Typical UK household electricity use:
- 1-2 bedroom home: 1,800-2,500 kWh per year
- 3 bedroom home: 2,500-3,500 kWh per year
- 4+ bedroom home: 3,500-5,000+ kWh per year
Simple Solar Sizing Formula
In the UK, 1kW of solar panels typically generates 850-1,000 kWh per year, depending on location, roof orientation and shading. So:
Annual electricity use ÷ 900 = Approximate system size in kW
Example:
If your home uses 3,600 kWh per year:
3,600 ÷ 900 = 4 kW system needed
At SolarTherm UK we install Aiko N-Type ABC Neostar 450-475W panels, meaning:
4 kW system ÷ 0.45 kW per panel ≈ 8-9 solar panels
Typical Number of Solar Panels in the UK
| System Size | Approx. Panels Needed | Suits |
| 3 kW | 6-7 panels | Small homes |
| 4 kW | 8-10 panels | Average 3 bedroom homes |
| 5 kW | 11-13 panels | Larger families |
| 6 kW+ | 14+ panels | High usage/EV owners |
Roof Space Requirements
A standard 450-475W solar panel measures roughly 1.7m x 1.1m. This means:
- 8 panels = ~ 16m² roof space
- 10 panels = ~ 20m² roof space
- 14 panels = ~ 28m² roof space
In the South East, your roof will ideally be south-facing, although east/west roofs are very effective, have a pitch of 30-40° and experience minimal shading from nearby trees, chimneys or buildings. Even in cloudy weather, solar panels generate electricity using diffused daylight, ideal for South East conditions.
What Are Your Solar Goals
The number of panels you need depends on what you want to achieve.
Reduce Electricity Bills
A 3-4 kW system is usually enough to produce significant savings.
Cover Most of Your Usage
Match system size to annual consumption.
Run an Electric Vehicle (EV)
Add an extra 2-3 kW of panels if charging an EV at home.
Sell Excess Power Back to the Grid
Through the Smart Export Guarantee (SEG), larger systems can generate export income.
Should I Maximise My Roof Space?
Many homeowners ask whether they should install as many panels as possible. In most cases, if you plan to stay in the property long term and are planning to add battery storage, EV charging or a heat pump in the future then maximising available roof space can improve long term ROI.
Energy prices are expected to continue rising and as solar panels typically last 30 years or more, installing slightly more capacity now can be financially strategic.
Do Solar Batteries Change How Many Panels I Need?
A battery doesn’t increase generation – it increases self-consumption. If you are installing a battery, you may choose in install a slightly larger system and future proof for EV charging or heat pumps. Proper system design at installation can ensure your inverter capacity and export limits comply with UK grid regulations in the future as your energy needs increase.
Final Answer: How Many Solar Panels Do I Need?
For most South East homes, the answer is between 8 and 14 solar panels, depending on annual electricity usage, roof size and orientation, shading and future energy plans. Every property is different – which is why accurate system sizing is critical for maximising performance and financial return. A MCS accredited installer, like SolarTherm UK, will ensure your system works for you and your energy goals.
Find out how much you could save using our Solar Calculator.
Smart solar starts with the right advice.
FAQs
How many solar panels does a 3-bedroom house need in the UK?
Typically, 9–10 panels (around 4 kW system).
Are 10 solar panels enough?
For an average UK home using 3,000–3,500 kWh per year — yes.
How many panels can fit on my roof?
Most semi-detached homes can fit 10–14 panels on the main south-facing roof slope.
Do I need planning permission?
Usually not (under permitted development rules), unless the property is listed or in a conservation area.
