Discount Pool Supplies and Spa Supplies

HOW TO APPROXIMATE THE COSTS
OF HEATING YOUR POOL OR SPA USING A GAS HEATER

There are numerous factors that affect heating costs, such as wind, heater efficiency, surface area, type of pool/spa construction, ambient temperature, whether or not the pool is covered, etc.. This is only intended to be used as a general guideline and should not be considered absolute. If carefully done, however, you should get a reasonably good idea of what your heating costs will be.

At the bottom of the page we have provided a calculator which takes most factors into account and will perform these calculations for you. 


First, we need to define BTU, or British Thermal Unit. This describes the amount of energy it takes to raise one pound of water, one degree Fahrenheit.

Second, we need to determine the number of gallons of water in the pool or spa. Assuming you have a 15,000 gallon pool, for example, you will be heating 124,650 lbs of water, since 1 gallon of water weighs 8.34 lbs.. To heat this water 1 degree will then require 124,650 BTU's.

Third, we need to factor in a heater's efficiency rating. Most heaters sold today typically run in the 80-83% efficiency range. Basically, this means that you lose about 20% of the BTU input as wasted energy. So, now you need 155,813 BTU's to heat this water 1 degree

Fourth, since we are billed in therms and not BTU's, we need to translate this into therms. (one therm = 100,000 BTU's). This pool, with today's average heater, would require 1.5 therms to raise the temperature 1 degree fahrenheit.

Fifth, we need to determine the cost of a therm. Gas costs vary greatly from area to area, and often by season, so you need to determine this from your gas bill. For the sake of simplicity here, let's assume a cost of $1.00 per therm. 1.56 therms times 100 cents per therm = $1.56. So, to raise the temperature of this pool, say 10 degrees, would cost $15.60, assuming, for simplicity's sake, that there was no heat loss.

A 200,000 BTU heater costs, $2.00 per hour to operate based on our per therm price of 100 cents. As you can probably tell, this heater uses 2 therms per hour. A 300,000 BTU heater uses 3 therms per hour, and so on.

Volume of Pool or Spa	Gallons - required
Average Wind Speed	MPH
Heater Efficiency	% - required
Desired Temperature Rise	degrees - required
Cost of Fuel per therm (from utility bill)	$ Required

Select the BTU rating of the heater:

55,000 BTU Heater
100,000 BTU Heater
125,000 BTU Heater
150,000 BTU Heater
175,000 BTU Heater
200,000 BTU Heater
250,000 BTU Heater
265,000 BTU Heater
300,000 BTU Heater
350,000 BTU Heater
400,000 BTU Heater