Rooftop and Plug-in Solar Calculator

Estimate how much of your electricity a rooftop or plug-in solar system could provide, and how much you could save each year.

Enter your postcode or address - we use it to look up how much sunshine your area gets

Your solar design

Annual electricity use 2,700 kWh

Your annual electricity use is the amount of energy your home consumes in a year. Your supplier bill will usually estimate the amount or it might be on your smart meter. We have provided typical values to make it easy to get started. One kWh is equivalent to boiling a kettle 10 times.

Not sure? Use Ofgem typical values ?

What type of solar are you interested in?

1 How much electricity does your home use?

This is the starting point - we use it to design your system and work out how much solar can cover. Check a recent bill, or use a typical value below.

2 How big is your home?

We use this to estimate how many panels your roof can fit.

3 Which way does your main roof face?

South-facing roofs get the most sun. Not sure? Pick "Not sure" - we'll assume a typical SE/SW facing.

4 Are you usually home during the day?

This affects how much of the solar electricity you use directly - and how much gets exported back to the grid.

2 How many panels?

Balcony or plug-in systems use compact 400W panels that clip onto railings or sit on a flat roof. No scaffolding needed.

3 Would you like a plug-in battery?

An optional battery stores surplus solar to use in the evening - no rewiring needed.

Want exact tariff rates or multiple roof faces? Switch to Expert designer

Are you home during the day?

If you're home during the day you'll use more solar electricity directly, so you save more. If you're out, more gets exported to the grid.

Your electricity rates

Day rate (p/kWh)

What you earn exporting (p/kWh)

Overnight cheap rate (p/kWh)

💡 We've pre-filled typical UK values - only change these if you know your exact figures. Check your electricity bill for your import (day) rate. The export rate (SEG) is what your energy supplier pays for surplus solar. Overnight rate: only fill this in if you're on Economy 7 or a similar time-of-use tariff - leave blank if not, and we'll use your day rate.

Electricity price rises 3.0% / yr

Electricity prices tend to rise over time. This adjusts future savings to account for likely increases - making solar even more valuable in later years.

Boost to home value £0

Solar panels can add value when you sell your home. Evidence varies - leave at £0 if you'd rather not include this.

Solar panels 3.80 kWp

Number of panels 10 panels

Orientation SE / SW (45°)

Roof pitch 35°

Each panel is roughly 1.7m × 1m and rated at 475W. Most UK roofs fit 8–16 panels. Tilt of 30–40° is typical - a standard pitched roof.

Battery storage

kWh

A battery stores spare solar energy to use after dark. A 5–10 kWh battery suits most homes. Set to 0 if you don't want a battery.

What this means for you

Updated ✓

☀️ Use your postcode to estimate your solar potential.

Install cost	Yr 1 saving	Yr 5 saving	Payback
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About your home

💡 We've pre-filled typical UK values - you only need to change these if you know your exact figures.

Annual electricity use (kWh)

From your bill or smart meter. ~2,700 kWh is typical.

Home during the day?

Day rate - what you pay (p/kWh)

Your standard electricity rate. Check your bill.

What you earn exporting (p/kWh)

What your supplier pays you for surplus solar sent back to the grid (Smart Export Guarantee).

Overnight cheap rate (p/kWh) (optional)

Default is 7p (Economy 7 or similar time-of-use tariff). Adjust if your tariff differs, or set to 0 if you have no cheap overnight rate.

Electricity price rises (%/yr)

How much prices might rise each year.

Quotes

How this tool works

Generation estimate

Annual solar generation is calculated using solar resource data from the MCS MGD003 dataset - the same data used by certified solar installers in the UK. The dataset provides annual yield figures (kWh per kWp) for 25 climate zones across the UK, at every combination of roof tilt (0–90°) and orientation (0–175° from south). Your postcode is matched to the nearest zone centre. The panel output assumes each panel is rated at 475 Wp; performance losses (wiring, inverter, temperature) are already embedded in the MCS figures.

How much solar you actually use

What fraction of generated electricity is actually used in your home (rather than sent back to the grid) depends on when you're home and whether you have a battery. These fractions come from the MCS MGD003 lookup tables, which model three occupancy types and a range of battery sizes against different generation and demand levels. A 90% cap is applied - it is not practically possible to cover all electricity from solar alone due to overnight and low-sunlight periods.

Financial estimate

Annual saving = (solar used in your home × your electricity rate) + (surplus exported × export rate) + overnight battery charging saving. The export rate is what you receive under the Smart Export Guarantee (SEG) or similar tariff.

Overnight battery charging saving

A battery can earn extra value by charging from the grid overnight at a cheap off-peak rate (e.g. Economy 7 at ~7–8p/kWh) and using that stored energy during the day instead of paying the standard rate. The number of overnight charging cycles available = 365 minus the cycles already used storing solar energy. Each cycle saves: battery capacity × 90% efficiency × (your day rate − overnight rate). This saving is set to zero if the overnight rate is not cheaper than the effective cost of using stored power.

Limitations

The MCS lookup tables cover generation and demand up to 5,999 kWh/year. Very large systems (typically >12 panels) or high-demand homes may approach this boundary; results in those cases are approximations. This tool does not account for shading, soiling, or system degradation over time. Always get a quote from an MCS-certified installer before making any purchasing decision.