Free Tool

UK Plug In Solar Savings Calculator

Enter your details below to see how much a plug-in solar system could generate and save — based on real PVGIS irradiance data for your region.

1. Your UK Region

Solar irradiance varies significantly across the UK — the South West gets roughly 25% more sun than Scotland.

2. Panel Orientation

Which direction would your panels face? Whether it's a balcony, garden, shed roof, or flat roof — face the direction your panels would point.

🧭Not sure which way you face? Open the Compass app on your phone, stand where your panels would go, and point it in the direction they'd face.

3. Mounting Angle

4. Kit Size

Most UK plug-in systems are 400–800W. 800W is the legal maximum for DIY self-connection.

5. How often are you home during the day?

This determines how much solar you use directly. Pick the best match.

6. Shading

Do trees, buildings, or overhangs cast shadow on your panels during the day?

7. Your Electricity Rate

pence per kWh

Find this on your energy bill. The Ofgem price cap is currently around 24.5p/kWh.

8. Your Kit Budget

Monthly Generation Breakdown

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

Apr–Sep Oct–Mar

🔋What about adding a battery?

A battery stores surplus solar you'd otherwise lose, letting you use it in the evening instead. Combined with a smart off-peak tariff, you can also charge cheaply overnight and use that stored energy during the day.

Daily surplus available

0.8 kWh

Battery boost

+£44 /yr

Total with battery (estimated)

£119 /yr

vs £75/yr without battery

How it works: The battery captures surplus solar during the day so you can use it at night when the sun is down — cutting your evening and overnight grid bill, not just your daytime use. On some kits the inverter is built into the battery pack itself, so the panels plug straight into the battery — no separate inverter to wire in.

Typical kit options: The EcoFlow STREAM Pro includes a 1.92 kWh LFP battery (expandable to 11.52 kWh, 6,000 cycles) from around £979. Standalone power stations start from £300 for 1 kWh.

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Save your results

We'll email you a summary of your personalised estimate — including your savings range, payback period, and monthly breakdown. You'll also be notified when BSI-certified kits launch (expected July 2026).

No spam. Unsubscribe any time. We never share your email.

Estimates based on PVGIS solar irradiance data, adjusted for orientation, tilt, shading, and system losses. Range shows conservative (base) to optimistic (+15%) estimates. Battery model assumes 2 kWh capacity, 90% round-trip efficiency, 65% seasonal factor. Actual output varies with shading, weather, and system efficiency.

Your Estimated Results

Annual Generation

612 – 704kWh/yr

Annual Saving

£75 – £86/yr

at 24.5p/kWh

Estimated Payback

4.6 – 5.3years

Based on £300 – £500 budget

20-Year Return

Up to £1,724

No energy price inflation assumed

CO₂ Saved

71 – 82kg/yr

☕ That's a coffee every 15 days — paid for by your panels

Our calculator uses established solar PV modelling principles:

1. Regional Irradiance Data

Solar irradiance figures (kWh/kWp/year) are drawn from the EU's PVGIS database. The South Coast receives approximately 1,100 kWh/kWp/year; Southern Scotland approximately 900 kWh/kWp/year.

2. Orientation Factor

South-facing panels receive the most sunlight. South-east and south-west are 95% as effective; east and west are 80%; north-facing panels receive only 40%.

3. Tilt Factor

The optimal UK tilt is 30–35° from horizontal. Vertical mounting (balcony railings) reduces output to approximately 75%. Flat mounting achieves about 85%.

4. Shading

We apply three shading levels: no shading (100% output), light shade such as partial morning or afternoon shadow (85%), and heavy shade from buildings or trees during peak hours (65%).

5. System Losses

We apply a 15% derating factor for inverter efficiency, wiring losses, temperature effects, dust, and soiling. This is standard for UK PV modelling.

6. Self-Consumption

Without a battery, you only save on electricity you use while generating. We model three scenarios: 75% if home most days, 50% for hybrid workers, and 30% if out during peak sun hours.

7. Savings Range

The conservative estimate uses the base calculation. The optimistic estimate applies a 15% uplift for best-case conditions with minimal shading. Actual results fall within this range.

Annual kWh = (Wattage ÷ 1000) × Irradiance × Orientation × Tilt × Shading × 0.85
Annual Saving = kWh × Self-consumption rate × Electricity tariff

Read our full guide to plug-in solar savings →