75 kW + 100 kWh Battery — Manchester Adult Community Education Centre
- System size
- 75 kW + 100 kWh battery
- Annual saving
- £19,200
- Payback
- 7.5 years
- Location
- Manchester
Scenario
An adult community education centre in Manchester — a 2,200 sqm 1980s single-storey purpose-built centre owned by Manchester City Council and operated under lease by an FE corporation as part of its Adult Education Budget (AEB) delivery — ran an annual electricity bill of £62,000 against a session calendar dominated by evening English language classes (Monday-Thursday 6-9pm) and Saturday family learning programmes. Daytime occupancy was minimal outside Wednesday morning ESOL provision.
The centre’s manager identified solar as a defensible climate action for the corporation’s wider AoC Climate Action Plan, but recognised that the use pattern would generate low self-consumption rates without battery storage. We were appointed in November 2024 after a tender shortlisting three local installers.
What we delivered
- System size: 75 kW PV on the main flat membrane roof (rail-mounted, ballast-free, south-east aspect, no shading)
- Panel count: 138 × 545 W panels (Trina Vertex S+)
- Inverter: 1 × 50 kW Sungrow string inverter
- Battery storage: 100 kWh in the centre’s plant cupboard (LiFePO4 chemistry, GivEnergy commercial) — designed to shift weekday daytime generation into evening English class consumption
- Monitoring: Live-generation display in the main entrance with weekly data feed into the ESOL Level 2 numeracy class
The 100 kWh battery was the critical design decision: pre-battery modelled self-consumption was 28%; post-battery 71%. The marginal £45,000 battery cost paid back inside 4 years against the additional self-consumption value.
Funding
Blended Greater Manchester Combined Authority (GMCA) decarbonisation grant + Salix Decarbonisation Loan:
- GMCA grant (40%): £37,800 (one-off capital grant from the GMCA Public Sector Decarbonisation Pot — separate from the AEB delivery budget)
- Salix Decarbonisation Loan (60%): £56,700 over 8 years at £7,100/year repayment
- Total capex: £94,500 at £945/kW (mid-scale, with the battery driving the per-kW cost up versus PV-only)
- Modelled annual energy savings: £19,200 — of which £13,000 came from improved self-consumption (28%→71%) and £6,200 from a combination of SEG export on Saturday daytime and avoided peak-tariff evening charging from battery discharge
- Net cash-flow positive year one: £12,100/year
The MCA grant element was critical to the business case — without it, payback would have been 8.5 years which is borderline for a community-facing centre with tight AEB-funded operating margins.
Compliance
- Manchester City Council landlord consent: Required because the centre operates under LA lease. The Council confirmed in 5 weeks via standard landlord-consent process. Architectural drawings and structural survey shared with the LA estates team.
- Asbestos R&D survey: Clear on the 1980s flat membrane roof area
- KCSIE 2025: Adult learners only (18+) but some 16-18 traineeship provision delivered alongside — DBS-cleared installers as a matter of course
- ESFA Post-16 Audit Code: ACE provision audited through ESFA AEB; capital projects funded outside AEB but the centre’s overall operations are within ESFA Post-16 Audit scope
- G99 DNO application: 75 kW exceeds 17 kW per phase, so G99 applied. Accepted in 11 weeks (faster than typical because of the smaller system size and clean DNO connection).
- Charity Commission: Not applicable (FE corporation operator, not a charity)
Programme
Phased install across the Christmas 2025 break (10 days of physical work — small system, no scaffold required, all roof access via mobile elevating work platform):
- Day 1-2: Mounting rail installation, ballast distribution
- Day 3-5: Panel installation, DC string commissioning
- Day 6-7: Inverter and battery commissioning, DNO witness testing
- Day 8-9: Live-generation display install, ESOL classroom data feed configuration
- Day 10: Handover, documentation pack delivery, first staff training session
No disruption to ESOL or family-learning sessions — the centre was closed over Christmas anyway.
Outcomes
- Year one actual generation: 71,200 kWh versus modelled 68,750 kWh (+3.6%)
- Year one actual energy savings: £20,400 versus modelled £19,200 (+6.3%)
- Self-consumption rate: 73% (slightly above modelled 71% due to a new Saturday afternoon community language class added in autumn 2025)
- Featured in the GMCA Decarbonisation Case Study round-up 2026 publication
- ESOL Level 2 numeracy class adopted the live-generation display as a teaching resource for graph-reading, percentage calculation, and unit conversion modules
- Family learning Saturday programme developed an “energy detective” activity for primary-age children visiting with parents — used the dashboard data
- MCA media coverage in Greater Manchester Climate Change news roundup
What the centre manager said
“Adult community centres often fall between the gaps in capital decarbonisation funding. We’re not a flagship FE campus that gets headline grant rounds, and we’re not a Local Authority asset that gets pure-LA capital. The MCA route was the unlock for us — and the Salix piece took it from financially marginal to genuinely positive. The 100 kWh battery is the critical design decision. Without it, our use pattern would have made the whole thing borderline. With it, we cover 73% of our electricity from the roof and the battery, and the rest from grid at increasingly off-peak tariffs.”