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An estimate for the first year, not a guarantee. Solar output varies from place to place and from year to year — check the workings, and verify against your accreditation scheme's requirements before quoting from them.
Installer tools · Solar PV
Five inputs, the recognised UK estimation method, and every figure behind the answer shown rather than asserted. Take me through it instead →
Generating it is not the same as using it. What would a battery change? →
~3,950 kWh/year
Most likely between 3,600 and 4,300 kWh — the method puts itself within about 10% for most systems.
The figure above uses the recognised lookup tables, so it is the same figure a certified installer will quote you. Those tables are built on a satellite dataset that has since been retired. Running the identical calculation on the data that replaced it gives 3,750 kWh — 5% lower.
Neither is a measurement, and the gap is not a mistake in either one. It is the honest width of the uncertainty — worth knowing before treating any single figure as a promise.
Sum of the module data-plate values at STC — the figure on the module label, not the inverter rating.
Source: MCS 032:2025 — The MCS Charitable Foundation
Resolved from the outward code of BS1 1AA.
Source: SAP 10.2 — BRE, on behalf of the Department for Business, Energy and Industrial Strategy
Degrees from horizontal.
Source: MCS 032:2025 — The MCS Charitable Foundation
Azimuth relative to due south. The method does not distinguish east from west.
Source: MCS 032:2025 — The MCS Charitable Foundation
Zone 5E, 30° inclination, 45° from south. Includes the 0.8 performance ratio.
Source: MCS Irradiance Datasets — The MCS Charitable Foundation; MCS permission — The MCS Charitable Foundation; MCS 032:2025 — The MCS Charitable Foundation; MIS 3002 — The MCS Charitable Foundation
Clear horizon, no near or far shading.
Source: MCS 032:2025 — The MCS Charitable Foundation
4.32 kWp × 914 kWh/kWp × 1 = 3948.48 kWh
Source: MCS 032:2025 — The MCS Charitable Foundation
3948.48 kWh/year, shown above as ~3,950
More decimal places make a number more precise. They do not make the estimate behind it more accurate — which is why the headline is rounded and this is not.
Calculated by the standard estimation method (MCS 032:2025 Section 3) — kWp × Kk × SF — using the Irradiance Datasets published by MCS, used with permission. This is an estimate for the first year of generation, given as guidance only. It is not a guarantee of performance: the output of a solar PV system cannot be predicted with certainty, because solar radiation varies from place to place and from year to year.