Here is a simple breakdown of power in vs power out:

1 - solar panel = 2.5 - 3 kilowatts of power produced per day.

1 - 5.5 kilowatt pool heater produces about 50,000 BTU per hour and uses about 5.5 kilowatts of power.

Over 2 days one solar panel produces enough power to run the pool heater for an hour.

In 30 days the solar panel produces the power to run the pool heater for 15 hours.

Since you only need to heat the pool for about three months and since over production from the solar system goes as a credit to CFE, one solar panel will provide enough power to heat the pool for about 2 hours each day during the cool time of the year.

Naturally you will use more power to get the pool to temperature and less power to keep it there. 

As well a solar blanket will go along way to conserve the heat you have put into the pool when you are not using it.

We can do the same calculations for a hot water tank and for an electric range or for any other power hungry appiance you may have.