Pick your usage pattern for a quick savings range
Add your UK postcode for a more location-aware estimate. We use postcodes.io to look up your coordinates and improve the local solar figures.
We match you to the nearest city for solar irradiance. If you enter a postcode above, this is auto-selected for you.
Larger systems generate more but may need a G98 notification above 3.68kW. Most balcony and plug-in setups stay at 800W or 1600W.
Which direction do your panels face? South gives the best annual output in the UK.
This determines how much solar you use directly. Pick the best match.
Appliances running during the day: fridge (~80W), router (~10W), always-on devices. Typical UK flat: ~200W.
Hours per day when your panels produce usefully. UK averages: 3.5h winter, 5.5h summer, 4.5h year-round.
Override the auto figure.
50-60% if out all day, 70-85% if home most of the day, 90%+ with smart scheduling.
Direct shading from trees, buildings, or overhangs reduces generation.
Ofgem Q2 2026 price cap (1 April to 30 June 2026) is 27.7p/kWh. Adjust if your tariff differs.
800W kit: £499. 1200W (3-panel): ~£750. 1600W (4-panel): ~£999. Stream Pro with battery: from £979. See all kits
What your energy supplier pays for electricity you export back to the grid. Typical SEG rate: 4-6p. Leave at 0 if not on a SEG tariff.
Holidays and extended absences reduce self-consumption. Leave at 0 if someone is always home.
A battery stores surplus solar and lets you charge cheaply overnight - boosting total savings significantly.
EcoFlow Stream Pro includes 1.92 kWh LFP battery (expandable to 11.52 kWh). Compare kits
Rate you pay to charge the battery from the grid overnight.
Full breakdown
Conservative / Expected / Optimistic columns reflect realistic variation in how much solar you use directly (self-consumption). Savings include both avoided import costs and any Smart Export Guarantee income. Figures assume flat energy prices. Real savings tend to be higher as energy costs rise. Battery costs are estimates only. How we calculate this.
Ready to start saving? Browse kits now.
EcoFlow STREAM kits are available from £499. Pick the right system for your setup.
Free. No spam. Unsubscribe any time.
Want to understand how we calculate your savings?
We explain how we model sunlight using real sun position data, use satellite irradiance records from PVGIS, and estimate how much solar you will actually use based on your home's baseload. Transparent assumptions, no inflated figures.
How our calculator works →How our calculator improves estimate accuracy
Most UK solar calculators hand you a single national average and call it done. Plug-in solar is different. A flat in a Manchester courtyard, a south-facing Bristol balcony, and a rural Highlands garden all receive very different amounts of sunlight. The closer we can model your actual location, the more honest the savings figure becomes.
1. Your postcode, used optionally. If you enter a UK postcode we validate it against postcodes.io, a free open-data service maintained by Ideal Postcodes. Only your postcode leaves your browser. We do not store it. In return we get back precise latitude and longitude for that postcode's centroid.
2. Coordinates feed live satellite data. Those coordinates are passed to PVGIS, the European Commission's satellite-irradiance database. PVGIS returns a location-specific annual yield for an 800W system tilted at your latitude's optimal angle. We then scale for the kit size, orientation, and shading you selected. On city-only runs we fall back to the nearest PVGIS city baseline.
3. Postcode-aware, city-anchored. When a postcode resolves, we also auto-select the closest city in the dropdown. That keeps the PVGIS monthly profile and sun-position model anchored to a sensible UK region, while the lat/lng refines the yield number itself.
4. Your own inputs still drive the rest. Postcodes improve the generation side of the equation. The self-consumption side (whether you are home, whether you run a battery, whether you have a smart tariff) still depends on what you tell the calculator. This is why we ask about baseload watts, solar window hours, and days away in advanced mode.
5. Degrades gracefully. If postcodes.io is unreachable, rate-limited, or the postcode is mistyped, we fall back quietly to the city-level estimate and say so in the note under the input. The calculator always produces a number. It just gets more accurate when a valid postcode is supplied.
Coming next. Future improvements in the roadmap: using the postcode region to adjust regional import-rate defaults, weighting shading by urban density, and surfacing postcode-level irradiance confidence bands.
How we calculate
Generation: Each city uses a PVGIS base yield (kWh/yr for 800W south-facing at 30-35° tilt, PR 0.82). We scale by system size, orientation factor, and shading factor. Where available, live PVGIS satellite data replaces the estimate.
Confidence range (Simple mode): We map your occupancy pattern to a self-consumption band - for example, someone home all day typically uses 58-82% of their solar directly, while someone out most weekdays uses 18-40%. The Conservative column uses the low end, Expected uses the midpoint, Optimistic uses the high end. Days away reduce the bands slightly.
Advanced mode: Self-consumption is computed from your actual baseload (watts) and solar window (hours/day): monthly daytime demand / monthly generation. The range is ±25% around this figure. Your shading factor reduces gross generation.
Savings formula: Annual saving = (self-consumed kWh × import rate) + (exported kWh × SEG rate). The SEG rate defaults to 5p/kWh - enter 0 if you are not on a Smart Export Guarantee tariff.
Battery model: Daily surplus solar = generation/365 × (1 - SC rate). Battery charges from this surplus (capped at battery capacity). Evening discharge = min(charged × 90% efficiency, night demand). Seasonal factor 0.65 applied for UK winter. Smart tariff saving = battery kWh × efficiency × rate spread × ~200 charge nights/yr.
Payback & return: Payback = total cost ÷ annual saving. 20-year return = (annual saving × 20) - total cost. No energy price inflation modelled - real savings likely higher. Full methodology.
Solar profile (SunCalc): Sunrise, sunset, solar noon, and peak sun hours use the open-source SunCalc library with your city's coordinates. Optimal tilt = latitude × 0.76 + 3.1° (Duffie & Beckman formula).
A solar calculator built for UK conditions
Most tools that call themselves a solar calculator are built around large rooftop systems and a single national sunlight figure. This one is different. It is a UK solar calculator for plug-in and balcony systems, the 800W class of kit that a renter or flat-owner can actually fit, and it uses your postcode to pull location-specific irradiance rather than a country average. If you have been looking for a solar calculator UK households can trust for small systems, that is the gap this tool is built to fill.
Solar savings calculator: what it estimates
As a solar savings calculator, the tool answers one question: how much money a plug-in solar kit would save you per year at your address. It models generation (the kilowatt-hours the panels produce, from PVGIS satellite data) and self-consumption (how much of that you use rather than export). Savings are the self-consumed units valued at your import rate, plus any exported units valued at your Smart Export Guarantee rate. The result is a yearly saving, a payback period, and a twenty-year return, given as a conservative-to-optimistic range rather than a single false-precision number.
Solar panel calculator: sizing and orientation
Used as a solar panel calculator, the tool lets you change the variables that decide output: system size in watts, panel orientation (south, east, west or north), and a shading factor for obstructions. It also reports the solar profile for your location: sunrise, sunset, solar noon, peak sun hours, and the optimal fixed tilt angle for your latitude. That last figure matters most for a static balcony or wall mount, where you set the angle once and leave it.
What this calculator does not do
It does not model large hardwired rooftop arrays, it does not quote installer prices, and it does not assume plug-in solar can be connected via a 13A socket without the compliant route. For an 800W system the compliant UK route in 2026 still runs through a CPS-registered electrician with a hardwired connection and G98 notification. The calculator estimates the energy and the savings; the G98 guide and BS 7671 page cover the installation rules.