How Many Solar Panels Do I Need in the UK?

A clear guide to calculating the right number of solar panels for your home based on electricity usage, roof suitability and realistic UK performance expectations.

When people search “How many solar panels do I need in the UK?”, they usually want a simple answer.

For most households, the number often falls between 8 and 14 panels. However, the only accurate way to calculate this is by reviewing your annual electricity consumption in kilowatt hours (kWh).

System sizing should always start with usage, not guesswork.

Step 1: Check your annual electricity usage

Your annual kWh usage is the foundation of solar system design.

You can find this on:

• Your yearly energy statement
  

• Your supplier’s online account
  

• Your smart meter portal

Typical UK annual electricity usage:

• 2,000 to 2,500 kWh – smaller homes
  

• 2,700 to 3,500 kWh – average 3-bedroom home
  

• 4,500 to 6,000+ kWh – larger or higher-demand households
  

Electricity consumption varies significantly between homes. Two similar-sized properties can have very different energy profiles depending on insulation, heating type and occupancy patterns.

Step 2: Understand how much one solar panel produces

Most modern UK installations use panels rated between 400W and 430W.

In UK conditions, a 400W panel typically generates around 340 to 380 kWh per year.

Output depends on:

• Roof orientation
  

• Roof pitch
  

• Shading
  

• Geographic location

South-facing roofs generally achieve the highest annual yield. East and west-facing roofs remain effective but distribute generation differently across the day. North-facing roofs usually produce less.

Generation figures are based on annual modelling rather than guaranteed daily output.

Step 3: Calculate your estimated panel number

A practical starting formula is:

Annual electricity usage ÷ average annual output per panel

Example:

If your home uses 3,600 kWh per year
And each panel produces roughly 360 kWh annually

3,600 ÷ 360 = 10 panels

This provides an estimated panel count needed to match annual electricity consumption.

Real-world savings depend on how much of that solar energy you use during the day rather than export.

How many solar panels does the average UK home need?

In practical installation terms:

• 6 to 8 panels suit lower-usage homes
  

• 8 to 12 panels suit most family households
  

• 12 to 16 panels suit higher-demand properties
  

• 14+ panels are common where electric vehicles or electric heating are used
  

For an average 3-bedroom home using around 3,000 to 3,500 kWh per year, 8 to 12 panels is typical.

However, professional design should confirm this using real usage data.

How roof space affects panel numbers

Physical roof space can limit how many panels can be installed.

A typical 400W panel measures approximately 1.7 metres by 1.1 metres. Ten panels usually require around 17 to 20 square metres of usable roof space.

Panel placement can be restricted by:

• Chimneys
  

• Roof windows
  

• Structural roof layout
  

• Shading from nearby buildings or trees

Not all roofs can accommodate the number of panels suggested by electricity usage alone.

Should you size to cover 100 percent of your usage?

Not always.

Solar panels generate electricity during daylight hours. If your household uses most electricity in the evening, a portion of generation will be exported to the grid.

Because export payments are typically lower than import rates, system design often focuses on:

• Matching generation to realistic usage patterns
  

• Avoiding unnecessary oversizing
  

The goal is balanced performance rather than maximum panel count.

What if your electricity usage will increase?

Future demand should be considered when sizing your system.

Electric vehicles can add 2,000 to 3,000 kWh per year depending on mileage. Electrification of heating can also increase electricity consumption.

If higher demand is expected, additional panel capacity may be appropriate at installation stage.

How much do solar panels cost in the UK in 2026?

Installed costs depend on system size, equipment and roof complexity.

Typical 2026 UK guide ranges:

• 3kW system (6 to 8 panels): £5,000 to £6,500
  

• 4kW system (8 to 10 panels): £6,000 to £7,500
  

• 5kW system (10 to 14 panels): £7,000 to £9,000
  

• 6kW+ systems: £8,500 to £11,000+

These figures usually include panels, inverter, mounting system, installation and certification.

Final cost varies depending on property layout and any required electrical upgrades.

How professionals determine the correct number of panels

Accurate system design involves:

• Reviewing the last 12 months of electricity usage
  

• Assessing usable roof area
  

• Modelling expected annual generation
  

• Confirming inverter sizing
  

• Managing required grid notification or approval
  

At iHeat, systems are designed around verified consumption data rather than fixed packages. Installation is completed by MCS-certified engineers, ensuring compliance with UK standards.

This approach reduces the risk of overestimating or underestimating panel requirements.

So how many solar panels do you need?

For most UK homes, the answer sits between 8 and 14 panels.

The only reliable way to determine the correct number is to review:

• Your annual kWh usage
  

• Your roof suitability
  

• Any planned increases in electricity demand

Solar systems perform best when matched carefully to real consumption rather than property size assumptions.

If you know your annual electricity usage, you can calculate a strong estimate immediately using the formula above.