Case study: Energy independence at a London tennis club
At the start of 2024, our client, a director of a London-based tennis club, was spending more than fifteen hundred pounds on grid electricity every quarter. A rooftop solar PV array and a lithium battery were commissioned in January 2025 and we were asked to measure the early impact.
““Since the panels went live our evening court sessions have been powered by the sun stored earlier the same day. Members love the green story and the savings speak for themselves.””
Project snapshot
Location: Harrow, North-West London
Completion: February 2025
System size: 9.12 kWp roof-mounted PV with integrated battery storage
Annual projected generation: 9 452 kWh
On-site projected self-consumption: 5 518 kWh direct plus 2 037 kWh via the battery (79.8 percent)
Grid independence: 43.5% of the club’s electricity now comes from its own roof
CO₂ avoided: 2 128 kg every year
Three-month performance review
We examined supplier invoices for February, March and April in the year before installation (2024) and the first three months of live operation (2025).
Year-to-date totals (Feb–Apr)
Between 22 February and 10 May 2025, the club received its first solar export payment:
£164.04 for 1 367 kWh of electricity sent back to the grid — nearly £15 per week during a sunny spring.
Headline results
Net grid import fell from 5,499 kWh to 2,615 kWh. A 52% reduction in only three months.
The total invoice cost dropped from £1,577.48 to £695.87. A saving of £881.61 or 56%.
In April 2025 the building became a net exporter, sending more energy to the network than it imported and receiving a bill of just £9.70.
How the system delivers these results
Dual-roof layout
Panels span both pitched and flat sections to catch sun from early morning until late afternoon. Careful string design keeps shading losses below 9%, supporting a performance ratio of 91.27%.
Battery integration
A lithium battery stores daytime surplus and releases it after sunset. Evening court lights, showers and clubhouse facilities now run mostly on stored solar power, avoiding peak-rate grid import.
Smart energy management
The inverter and battery work in tandem with the existing distribution board. No operational changes were needed for staff or members.
Environmental impact
Avoiding 2 128 kg of CO₂ each year is equivalent to:
Taking one petrol car off the road
Planting about 97 mature trees
Future projection
Annual electricity spend expected to fall to about £400, a saving of roughly £1 500 compared with the pre-installation baseline.
May to September: Court lights powered almost entirely by stored solar. Bills are likely to equal the standing charge only.
October to January: Shorter days will raise grid import slightly yet bills should stay under £170 a month.
Looking ahead
If February-April figures continue, the club is on course for an annual electricity bill of roughly £400, compared with about £2,000 before installation. Pay-back is projected at six to seven years, after which the system will produce free, zero-carbon power for at least another 15 years.
Lessons learned
Solar works even on a busy urban site with partial shading.
Adding a battery multiplies the benefit because evening consumption is the most expensive.
Continuous monitoring is essential. The half-hour data of the smart-meter will allow us to refine the savings model and confirm payback.
Ready to serve your own clean energy?
Green Planet Makers designs and installs turnkey solar and storage systems for sports clubs, community buildings and commercial sites. Contact us for a free desktop assessment and find out how much you can save.
