Help with heating cost estimator :) Please!

[MelP]

Hi! Using the Excel Heater Calculator I found on here, I estimated the cost to heat our pool at $9,000,000 lol. Can someone help me?
Our pool is 18X25, 5 feet deep. I do not know the current pool temperature, but I live in Southern California, it has only been in the mid-60's this week but it about 75 today and will be close to 80 in a couple of days so I estimated I wanted to raise the temperature 20 degrees. I attached our gas bill too.
We have a Pentair 400, which I looked up was 400,000 btu.
This is a new pool and we have not tried to heat it yet because it has not been very warm and gas prices are higher than normal. Thanks for any help!

 

[mknauss]

Hard to read. Looks like you need to check pool volume and what you pay per therm. $68/30 is about $2.25 per therm.

 

[MelP]

Hard to read. Looks like you need to check pool volume and what you pay per therm. $68/30 is about $2.25 per therm.

Thank you! I see that the excel estimates it will be 50 therms to heat so I guess I multiple that by the cost per therm.

 

[JoyfulNoise]

It's $68 total (gas, delivery and taxes) for 35 therms, so about $1.94/therm. That's pretty high. Don't expect California gas prices to go lower. The regulators in CA are looking to phase out natural gas use as much as possible (along with all other fossil fuels), so you can only expect that number to go up over time. Roughly speaking, a 400,000 BTU/hour heater running at 85% efficiency (standard for gas heaters) will raise a 17k gallon pool's temperature by 0.4 deg F per hour. That's assuming very idealized conditions but it's close enough. If you hope to trap any of that heat and not waste it, you'll need to cover the pool with a solar blanket, especially overnight, as evaporative heat loss is the biggest loss of heat.

400,000 BTU's = 4 Therms

So, at your gas costs, the heater will cost roughly $7.76 per hour to run. So if you ran the pool heater 8 hours per day, it will cost you $62 per day.

Sorry, one thing to note - it looks like you are allotted 30 therms per month. As your last bill shows, when you exceed your allotment, 5 extra therms in that case, you were charged more for that. That's a "tiered rate" system. You should find out from your gas supplier if there are more tiers that they charge at because running the gas heater will easily exceed your baseline allotments and the rates may get higher and higher as you go into high tiers. We experience that around here with water bills - we are allowed 8CCF of water at the base rate. Once you exceed 8CCF, every additional CCF up to 15 is double the price. After 15CCF, the price per CCF nearly triples from the baseline rate . It's intended as a punishment for those that use excess water ... gotta love the regulators ...

 

[ajw22]

Roughly speaking, a 400,000 BTU/hour heater running at 85% efficiency (standard for gas heaters) will raise a 17k gallon pool's temperature by 0.4 deg F per hour.

Check your work.

17,000 gallons = 136,000 lbs of water.

80% efficiency of 400K heater is 320,000 BTUs.

That should raise the temperature by 2.35 degrees/hour.

In round numbers each degree of heat will cost around $4 for @MelP in CA.

In NJ NG costs me $1/therm.

 

[JoyfulNoise]

numerator and denominator got swapped … and water weighs 8.34 pounds per gallon so YOU check YOUR math too, bub…

2.39°F/hour

 

[ajw22]

numerator and denominator got swapped … and water weighs 8.34 pounds per gallon so YOU check YOUR math too, bub…

2.39°F/hour

2.35 vs 2.39 is close enough for government work.

Round down 85% efficiency to 80% and 8.34 to 8 lb so my feeble mind can deal with round numbers.