A Pool's Running Costs, Worked End to End
One pool, four upgrades, every number on the table. This is the calculation we run for real enquiries, applied to the UK's most representative pool: outdoor, 8×4 metres, heated to 28°C from May to September, currently gas-heated with a tired single-speed pump.
The baseline: where the money goes today
Our example pool holds 48,000 litres. Uncovered, it loses heat relentlessly — evaporation alone strips around 5°C a week in a breezy garden — so the gas boiler supplies roughly 11,000kWh of heat across the season. At 2026 gas prices (7p/kWh, 85% boiler efficiency) that is about £900. The 1.1kW single-speed pump grinds eight hours a day all season: another 1,350kWh of electricity, £350 at 26p. Round it to £1,040 a season heating, £350 pumping — call the baseline £1,390, and note the heating share is the bigger and softer target.
Step one: the cover — £300 spent, ~£420/season saved
A bubble cover used overnight and on non-swimming days cuts evaporation losses by 50%+ and total heat demand by roughly 40% on a typical usage pattern. Heat demand falls from 11,000 to about 6,500kWh; the gas bill drops from £900 to around £530. The £300 cover repays itself before August of year one, which is why every page on this site refuses to size solar for an uncovered pool — full reasoning on the covers page.
Step two: the pump — £750 spent, ~£250/season saved
A variable-speed pump running longer hours at low speed filters the same water for a fraction of the energy (pump power falls with the cube of flow rate). Seasonal pump consumption drops from 1,350kWh to roughly 400kWh: £350 becomes £100. Fitted cost £600–£900; payback inside three seasons, and the quieter plant room is free.
Step three: the heat pump — £3,200 spent, heating bill halves again
Replace the gas boiler with an 11kW inverter pool heat pump. The covered pool's 6,500kWh of heat now arrives via a seasonal COP around 5, consuming roughly 1,300kWh of electricity: £340 at grid prices, versus £530 of gas — cheaper already, but the real purpose is converting heat demand into an electrical load that solar can serve. (Details of sizing and controls on the pairing page.)
Step four: the panels — £4,800 spent, the bill nearly vanishes
A 3.6kWp MCS-installed array (0% VAT until March 2027) generates about 3,200kWh a year in middle England. Through the swimming season it covers the heat pump's 1,300kWh and the pump's 400kWh almost entirely when the heating window is timed to daylight — solar-priority controls push self-consumption of pool loads above 80%. Residual grid purchases for grey weeks: roughly £80 a season. Off-season, the array serves the house and exports the rest, worth £250–£350 a year against household bills and SEG income at 2026 tariffs.
The ledger, honestly totted
Total invested: about £9,050 across the four steps. Seasonal pool running cost: £1,390 down to roughly £180 (residual grid top-ups plus chemicals-grade electricity), saving £1,200 a year — plus the array's £250–£350 of off-season household value. Simple payback on the whole programme: around six years, after which the pool effectively swims free for the panels' remaining warranted life. Each step also stands alone — the cover pays back in months, the pump in three seasons, the heat pump against gas in five — so the programme survives being done gradually as budget allows, in exactly this order. Costs for every component sit on the costs page; differences for indoor pools (year-round demand changes the array sizing logic) are on the indoor vs outdoor page.
Your pool will differ — volume, exposure, season, region, and how warm your household actually likes the water all move these numbers. Send the specifics through the contact form and we will run this exact ledger on your pool, assumptions shown, within one working day.