How big should my solar system be?
Short answer
Size is limited by roof space and budget, then judged against your annual use and when you use it. MCS quotes must show expected generation and how much you would use yourself, with and without a battery, based on whether someone is home in the day. EVs and heat pumps raise demand, mostly in winter.
Last checked 24 September 2026 · 1 source
In more detail
- MGD 003 occupancy archetypes: home all day / half day / out all day.
- Winter output is small; batteries plus time-of-use tariffs help in winter.
The facts, dated
- 01MCS self-consumption estimate uses occupancy archetypes and assumed annual consumption (MIS 3002 4.1.6)
standard · UK · checked 24 September 2026 · MCS
What we saw in the field
[QA review 2026-09-24] I-2 UNVERIFIABLE: installer claim that a high-use home with 20 panels covers 30-50% of use; customer 1 covered ~37% (5.87 MWh in ~11 months) - consistent but MGD 003 cannot test homes over 6,000 kWh/yr. H-6 CONTRADICTS (corrected from 'consistent'): the homeowner's June 2023 figures (import 20 kWh, export 857 kWh) exceed PVGIS June 2023 total generation of ~808 kWh for a 5.6 kWp SW/NE array; implausible as stated. H-4: ~12 kWh/day before a heat pump. C2-4 AGREES: ~10.5 MWh from 13.5 kWp (~780 kWh/kWp) matches MCS zone 3 with half the array north-facing. I-8 AGREES (proxy): median wattage in MCS-listed module names rose from 330 W (2019) and 355 W (2020) to 450 W (2022) and 480 W (2023); proxy includes commercial modules and recertification dates.
Sources
Last checked: 24 September 2026