Tell us about yourself!
Sadly Glumpy, I think you need to look at basic thermodynamics tables. Your calculations are WAY off. Using a 1Kw heater will heat 10L of water 1 degree is about 40 seconds. Not an hour like you suggest. This heater on average will heat up about 1000L of water a total of 5 degrees in 6 hours. Not bad. But yes, not enough for a full size pool.