"In my garden I have a 24-ft x 12-ft x 4-ft deep, 6400-gallon oval above ground pool; this was installed to replace a rather tired 15-ft diameter 4-ft deep 4000-gallon pool. An under-ground power cable was originally installed with only enough capacity to supply a 6-kW heater. To upgrade the cable would have meant digging up a patio and tunnelling under a wall. I thought a 6-kW heater would not be sufficient but in an attempt to rescue the situation, without upgrading the cable, I lined the pool floor and walls with 20mm thick expanded polystyrene sheet (the heavy duty version that will support 10.2 tonnes per square metre)."
"This pool has been in use now for 3 years, it is heated to a constant 28°C from mid-April to mid-September. During good sunny weather the heater switches off for days on end, if the solar cover is not stripped off on a daily basis the temperature can rise dramatically."
"The running costs of this pool are significantly less than its smaller non-insulated predecessor, with heat up time remaining approximately the same."
The Conclusion Is Simple:
To Insulate A Pool Pays Dividend Upon Dividend
And will repay the purchase cost of the insulation materials usually within the first season. To go further and liken it to heating a room in your home in mid-winter, leaving the doors and windows open - the house will never reach temperature. Close the 'doors & windows' on your pool (insulate it). Keep that valuable heat where you want it, don't heat the neighbourhood.