How much electricity does a solar panel produce in the UK?

A typical 400W solar panel produces approximately 380-420 kWh per year in the UK, depending on location, orientation and shading. South-facing panels at 30-35° pitch in southern England produce the most. A 10-panel (4 kWp) system typically generates 3,500-4,200 kWh/year.

What size solar PV system do I need?

A typical UK household uses 3,500-4,500 kWh/year. A 4 kWp system (10 panels) covers most of this but you won't use all generation directly. With a battery, you can store excess for evening use. Oversizing slightly (5-6 kWp) is common to maximise self-consumption and export income.

How much roof space do solar panels need?

Modern 400W panels are approximately 1.75m² each. A 4 kWp system (10 panels) needs about 17.5m² of roof space. A 6 kWp system (15 panels) needs about 26m². Allow extra space for setbacks from roof edges (typically 300mm).

Does orientation matter for solar panels?

Yes, significantly. South-facing is optimal (100% yield). South-east/south-west reduces yield by about 5%. East or west facing reduces yield by about 20%. East-west split arrays can be worthwhile for self-consumption as they spread generation across the day.

How long do solar panels last?

Modern solar panels have a design life of 25-30 years with performance warranties guaranteeing at least 80% output at 25 years. Actual degradation is typically 0.3-0.5% per year. Inverters last 10-15 years and may need replacing once during the panel lifetime.

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Solar PV Array Calculator

Calculate solar panel array size, annual energy yield and installation costs based on UK regional irradiance, roof orientation and panel specifications.

UK RegionAffects annual solar irradiance

Roof OrientationSouth-facing is optimal

Panel Type400W panels are now standard

Number of Panels

Panels in the array

Roof Pitch

30-35\u00B0 is optimal for UK

Price per Panel

Supply cost per panel

How We Calculate This

This calculator estimates solar PV array output using UK regional irradiance data.

The formula

Annual yield = System kWp × Regional yield × Orientation × Pitch × Shading

Regional yield: 850-1050 kWh/kWp depending on UK location
Orientation factor: south 100%, east/west 80%
Optimal pitch: 30-35° for UK latitude
Panel degradation: ~0.5% per year

Frequently Asked Questions

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Last updated: March 2026

All calculations are estimates. Verify with your supplier.