Why batteries make church solar economics work
The fundamental challenge with parish church solar is self-consumption: Sunday-only buildings use very little electricity during the week when solar is generating. Without storage, the parish exports most of its generation to the grid at 8–12p/kWh under SEG, when retail electricity costs 22–28p/kWh. The economic mismatch is significant.
Battery storage shifts the picture. A 10 kWh battery on a typical 15 kW parish system stores midday surplus and releases it during evening services, choir practice, weekday hires, or for the parish hall next door. Self-consumption rises from 30–40% to 60–80%. Annual savings roughly double for the same solar capacity.
Modern lithium iron phosphate (LFP) batteries have 10–15 year design lives, are non-flammable (different chemistry from lithium ion in cars), and can be wall-mounted in the church boiler room or vestry. Typical parish installations use 5–15 kWh; larger combined church+hall sites use 15–30 kWh.
Sizing the battery to your parish
Rule of thumb: battery capacity (kWh) should be roughly equal to the parish's average daily electricity consumption from the grid. For a typical parish: church + hall electricity ~6,000 kWh/year = ~16 kWh/day average = 10–15 kWh battery is the right starting point.
Oversize the battery and you pay for capacity you won't use. Undersize and you miss the self-consumption uplift. The sweet spot for most parishes: a battery that captures the difference between weekday baseload generation and demand.
For parish hall-led installs (Phase 1 of hall-first strategy), a smaller battery (5–10 kWh) often makes sense because hall daytime usage is higher to begin with. For church-only Phase 2, a larger battery (15–25 kWh) typically pays back because of the Sunday-only consumption pattern.
Battery cost and payback
Typical battery capex 2026: 5 kWh £2,500–£4,000; 10 kWh £4,500–£7,000; 15 kWh £6,500–£10,000; 20 kWh £8,500–£12,500; 30 kWh £12,000–£18,000.
The additional saving from a battery is typically £500–£2,500/year depending on parish use pattern and battery sizing. Payback on battery capex alone (excluding solar) is typically 6–11 years. Combined with solar capex, total system payback usually shortens by 1–3 years.
Battery installations are typically eligible for the same grant routes as solar (Buildings for Mission, diocesan capital programmes, LPW VAT scheme for listed buildings). Most awards we secure now cover the combined solar+battery package.
Limited backup capability
Most parish battery installations include a limited 'backup' mode — the battery continues to power critical circuits during a grid outage. Typical configuration: hall lighting, vestry, security, communion preparation. Not usually the whole church (which draws too much during services).
Backup capability is not the principal economic driver for most parishes, but PCCs in rural areas with unreliable grids find it valuable. The marginal cost is typically £400–£1,200 for the backup-ready inverter.
Common questions
Do we need a battery to make solar work?
Not strictly. Solar without battery still works financially with grants. But for Sunday-only churches the battery roughly doubles annual savings and is usually worth including from the outset.
What battery brand do you use?
We're brand-agnostic but typically specify lithium iron phosphate (LFP) batteries from Tier 1 manufacturers (BYD, Pylontech, Givenergy, Huawei). All come with 10-year manufacturer warranties and have proven safety records.
Where does the battery go?
Typically the church boiler room or vestry on a wall-mounted bracket. Footprint is small (50cm × 30cm × 90cm for 10 kWh). No special ventilation required. Visibility from inside the church is usually zero.
What if the battery fails?
10-year manufacturer warranty covers cell failure. We provide IWA-backed workmanship warranty on the install. Failed batteries are typically replaced within 2–4 weeks; the solar continues working without the battery in the meantime.
Is faculty required for the battery alone?
Usually yes, as part of the wider solar faculty. Standalone battery retrofits to existing solar systems sometimes don't need faculty if the work is purely electrical and doesn't affect fabric.