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What is solar self-consumption and why does it matter?

Short answer

Self-consumption is the share of your solar electricity used in your home rather than exported. It matters because each self-used unit saves the full import price (26.32p/kWh under the October–December 2026 cap) while exported units earn far less. MCS requires installers to quote it with and without a battery.

Last checked 24 September 2026 · 3 sources

In more detail

  • Self-consumption (% of generation) ≠ self-sufficiency (% of your consumption met by solar); MCS requires both in kWh and %.
  • MCS method (MCS 032 s.5 / MGD 003): occupancy archetype + annual use (1,500-6,000 kWh) + PV generation (<6,000 kWh) + usable battery kWh -> lookup.
  • Occupancy unknown -> use 'in half the day'.
  • EV, heat pump, immersion diverter loads are added separately; total self-consumption capped at 95% of generation and of use.

The facts, dated

  1. 01
    In half day, 3,500-3,999 kWh use, 2,700-2,999 kWh generation: PV-only self-consumption — 28.6 %

    standard · UK · checked 24 September 2026 · MCS

  2. 02
    Same with 8.1-9.1 kWh battery — 82.2 %

    standard · UK · checked 24 September 2026 · MCS

  3. 03
    Ofgem cap electricity unit rate 1 Oct-31 Dec 2026 (DD, no VAT) — 26.32 p/kWh

    regulation · GB · checked 24 September 2026 · Ofgem

  4. 04
    MCS cap on total self-consumption — 95 % of generation and of consumption

    standard · UK · checked 24 September 2026 · MCS

What we saw in the field

[QA review 2026-09-24] I-2 UNVERIFIABLE: the 30-50% figure is self-sufficiency, not self-consumption; no source for homes >6,000 kWh/yr. | Earlier notes: Installer claim 'a high-use home with 20 panels might cover 30-50% of use' and Customer 1's '~37% of use' are self-sufficiency, not self-consumption. They sit in the range MCS 032's worked example gives (23% PV-only, 65% with a 9 kWh battery for a 3,500 kWh home). Large homes with EVs/heat pumps are outside MGD 003's 6,000 kWh scope, so this can't be tested directly. Plausible.

Sources

Last checked: 24 September 2026