swimming pool with clear water and entry ladder

Enjoy Added Seasonal Use of Your Pool or Spa

Natural gas provides reliable, cost-effective pool and spa heating to help owners extend their open season.

Pool Heating

Comfortably extend your pool's swimming season by installing a natural gas pool heater.

Next, use our pool heating tips for optimal efficiency:

  • Keep a thermometer in your pool to pinpoint your ideal temperature. Although 78 to 82 degrees is a good general rule for comfortable pool temperature, how warm you keep your pool depends on your personal preference.
  • Keep your thermostat at the lowest comfortable setting. The American Red Cross Each additional degree of heat could add to your monthly fuel cost and use more energy than necessary. Mark the “comfort setting” on the thermostat dial. This will prevent accidental overheating and the waste of energy.
  • Lower the thermostat to 70 degrees when the pool won’t be used for three or more days. For longer periods, shut the heater off. You will save money on fuel consumption and help conserve energy. Less energy is required to reheat a pool for a weekend or special occasion as opposed to maintaining a constant temperature all week. For weekend swimming, turn your thermostat up to the “comfort setting” on Friday night and back down to 70 degrees on Sunday evening.
  • Shield your pool from wind. Winds above three to five miles per hour can lower the pool temperature significantly. A hedge, cabana or a decorative fence can provide an effective windbreak.
  • Use a pool cover when the pool is not in use. A good bubble pack or dual filament pool cover can reduce heat loss by 70 to 90 percent. Using a pool cover helps prevent evaporation. Every gallon of water that evaporates from a pool takes heat with it. A typical uncovered pool loses 1 to 1.5 inches of water a week through evaporation. For a 20 by 40- foot pool, an inch of water amounts to 500 gallons.
  • A larger-sized heater will increase the energy savings you can obtain when you plan to use the pool. A heater that is too small will allow significant loss during the heat-up period.
  • Get a pool-heater maintenance check every year. The cost is minimal, and the service will keep your heater working efficiently for many years to come.

Spa Heating

Choosing the right heater for your spa or hot tub is as important as which spa or hot tub you select. Affordable natural gas spa heaters offer the most economical method for heating your new or existing spa or hot tub, whether it’s a portable or permanent in-ground installation.

Next, use our tips for heating spas and hot tubs to maximize efficiency:

  • The heater size you choose determines how quickly your spa or hot tub will heat. Many spa owners want their heaters to be capable of raising the water to the desired temperature in about an hour. The simple fact of the matter is that fast heating costs no more than slow heating. A larger heater can actually cost less to operate than a smaller heater because the shorter warm-up time minimizes heat loss to the air.
  • The larger the heater, the faster you can bring your spa or hot tub to the desired temperature.For example, a 125,000 BTU/hour heater will heat a 400-gallon spa to 100 degrees in 63 minutes from a standby temperature of 70 degrees. A 175,000 BTU/hour heater will achieve the same result in 45 minutes.
  • Use a cover whenever the spa is not in use (or is heating up). The cover helps your spa or hot tub reach the desired temperature faster and retain heat longer.
  • Use a thermometer to determine water temperature – not your body parts! Physicians generally recommend avoiding water above 104 degrees.
  • Avoid damaging buildups of salts and calcium by draining your spa or hot tub regularly (follow the manufacturer’s recommendations).
  • Don’t run the heater more than you need to – there’s no reason to have it at your desired temperature unless you’re actually using it.
  • Get a maintenance check-up annually. The cost is minimal and the service will keep your spa heater working efficiently for many years to come.

Calculating Operating Costs

Use this formula to help you determine the operating cost of running a pool or spa heater.

Note: The heat loss of a pool or spa varies with the weather, so the predicted cost of operation may significantly vary from actual operating cost.

Formula for predicting how much it costs to run a gas pool or spa heater:

Cost of gas per therm x Input of heater = Cost per hour


A 250,000 BTU heater with a gas cost of 0.86 per therm
(1 therm = 100,000 BTU)
0.86 per therm x 2.5 therm per hour = $2.15 per hour