Mike the Poolman


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The gas cost to run a pool heater- 2021

June 26, 2020

What is the gas cost to run a pool/spa heater in 2021?

I last published this article in 2012. Gas prices with PG&E have obviously gone up since then!

Here’s a common question I answer: “Mike, I’d really like to use my heater more but I’m afraid of how much it will cost. How much does the gas cost to run my heater ?”Swimming pool & spa gas heater
My answer is always the same: ‘size matters, but…’
The but is we can still figure a pretty reliable median number based on the numbers provided by PG&E on our monthly Energy Statment.

The most common heater in residential applications is 399,000 BTU’s (British Thermal Units). We just refer to it as a 400 or 400,000. If you have a heater for your pool/spa in Northern California chances are it’s a 400. Other sizes found are 350,000, 333, 275, 250 and 175. The larger the heater the more output and the faster you’ll heat the body of water.

Gas Math

The tricky part of the equation is knowing how much you pay your local utility company per therm. I live in Folsom and our natural gas is provided by PG&E. I checked my bill and found that we pay $1.36 cents to $1.89 per therm, up from 92 cents – $1.40 in 2012. In addition, there is a 4 cents per therm surcharge for “PPP” (per my bill: Gas Public Purpose Program Surcharge: “Used to fund state-mandated gas assistance programs for low-income customers, energy-efficiency programs, and public-interest research and development.”)

My calculations come out to $1.63 per therm plus the $.04 surcharge equals a gas cost of $1.67 per therm, on average.

A 100,000 BTU heater uses 1 therm of natural gas per hour, so a 400,000 heater consumes 4 therms an hour. 4 therms an hour x $1.67 = $6.68 per hour.  So the magic number based on the most common 400,000 BTU pool/ spa heater is $6.68 per hour in gas cost to run your heater. Keep in mind, we’re not talking about how long it takes but how much it costs. ‘How long it takes’ has many more factors and that topic is for another blog article.

Mike the Poolman
Pool Service & Repair in Folsom, California

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