Thermalec 18kw

Suitable for pools up to 10 500 gallons based on 7 hour heating period, maximum temperature of 75F, and use of a suitable pool cover.
Assuming pool is based in the South of England.
For pools in the North multiply heater size by 1.5-1.7 depending on exposure of the pool.
Requires installation to current UK Electrical Regulations and standards by a suitably qualified electrician