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Solar · Advice

What share of my electricity will solar panels cover?

Short answer

Over a year, a typical system covers roughly a third to a half of a household's electricity. The rest comes from the grid, mainly in winter and at night. A battery lifts this, but no UK rooftop system covers December demand for a high-use home. Generating more than you use over a year still means importing in winter.

Last checked 24 September 2026 · 1 source

In more detail

  • PVGIS London south: December produces ~34 kWh/kWp vs ~125 in June: roughly a quarter.
  • Self-sufficiency rises with battery size and daytime use; it falls with electric heating demand concentrated in winter.
  • Field Customer 1: ~5.87 MWh in ~11 months covering ~37% of use (high-use home with EVs/battery).
  • Field Customer 2 generated more than annual use (~10.5 MWh) yet expected net-positive costs only late March to mid-October.

The facts, dated

  1. 01
    PVGIS London south 30: June 125, December 34 kWh/kWp — 125/34 kWh/kWp

    market_data · England · checked 24 September 2026 · PVGIS (EU Joint Research Centre)

What we saw in the field

[QA review 2026-09-24] I-2 UNVERIFIABLE (30-50% for a high-use 20-panel home consistent with C1's 37% but outside MGD 003 scope; ). C2-5 AGREES. | Earlier notes: Installer claim '20 panels might cover 30-50% of a high-use home' agrees with Customer 1 (37%) and seasonal physics; Customer 2's seasonal net-positive window (late March-mid October) agrees with PVGIS monthly shape.

Sources

Last checked: 24 September 2026