APPROXIMATE THE COST
OF HEATING YOUR POOL OR SPA USING A GAS POOL HEATER
numerous factors that affect heating costs, such as wind, humidity,
heater efficiency, surface area, type of pool/spa
construction, ambient temperature, whether or not a cover is used, etc.. This is only intended as a
general guideline, however, you should get a reasonably good idea
of your heating costs.
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 pool 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 pool heater uses 2 therms per hour. A
300,000 BTU heater uses 3 therms per hour, and so on.