There are major shifts on the horizon for the pool heating industry as the move towards building decarbonization and energy efficiency continues to gain momentum. These changing expectations extend to new construction specifically and will require professionals to adjust their practices around pool heater sales and installations, as well as how they educate customers about their options.

For decades, the primary method of heating pools and spas in California and much of the West Coast has been with gas heaters. However, concerns over the environmental impact of gas-powered appliances are mounting, leaving state and local governments, as well as individual consumers, to explore more eco-friendly alternatives. Of particular concern, several local governments in the state are pursuing building-decarbonization ordinances.

Because of this movement, heat pumps may eventually become the prevalent method of pool heating. Pool professionals should prepare for this possibility. It will be equally important to educate consumers about the differences in heat-up time and operational costs of the various pool heating options so they can make informed decisions.

Legislation is Already on the Books

Contrary to rumors, California has not enacted a law banning gas heaters or gas lines.

However, the state has encouraged local governments to pass “reach codes,” which are ordinances that put limits on new gas lines or ban them entirely. These codes do not impact existing structures, so residents who have pools and spas that are already gas-heated will not be affected. However, at least 40 California cities and municipalities —and counting — have enacted building-decarbonization codes for new residential and/or commercial low-rise buildings. This means that homeowners in those areas who want to install new pools or spas past a certain date may be unable to heat them with gas.

Many other cities have enacted ordinances supporting balanced energy portfolios, taking a more measured approach to regulating energy efficiency.

Other states will likely pursue building-decarbonization ordinances. Washington, Oregon and Massachusetts currently are considering similar moves to mandate all-electric new construction. It’s important for pool professionals to stay ahead of pending ordinances in their local communities and reach out to legislators to make their voices heard.

Gas Swimming Pool Heaters

In California and some other western states, gas heaters are by far the most popular way to heat swimming pools and spas given the lower cost of natural gas compared with electricity, as well as quicker heat-up times.

Regardless of the external air temperature or humidity, a gas heater will always provide a constant heat output. For example, a gas heater rated at 400,000 BTUs can heat a 600-square-foot swimming pool that holds 18,000 gallons in approximately 12 hours from 50°F to 82°F. Doing this, it will use 4 therms per hour. The 2021 projected natural gas price in Sacramento is $1.77 per therm, according to the Sacramento Municipal Utility District (SMUD). This means it will cost about $7.08 per hour for 12 hours or about $85 to heat the pool just a single time.

A 20-square-foot spa holding 500 gallons can be heated in just 33 minutes from 50°F to 102°F. In Sacramento, Calif., this would cost $3.50, according to SMUD. Many pool and spa owners consider these costs to be minimal compared to the speed at which the gas heater works.

Other advantages of gas heaters include quiet operation, low installation costs when a gas line already exists, and the ability to install indoors with proper venting.

However, gas heaters are the least energy-efficient, operating at a minimum energy efficiency of 82%. This means that for every $100 of gas, the heater is generating at least $82 worth of useful heat. While customers once overlooked this inefficiency because of low natural gas prices, they are less forgiving today, especially considering the other disadvantages — their production of carbon dioxide and contribution to greenhouse gasses, and the need for a gas line, which costs even more for propane.

Heat Pumps


Heat pumps, also known as electric pool heaters, do not actually generate heat from the energy they consume. Instead, they capture heat energy from the air and transfer it to the water.

This means that, where gas-powered units always put out the same amount of heat regardless of the outside air temperature, the output of heat pumps will vary considerably depending on the outside air temperature. The warmer the air is, the more heat output a heat pump delivers. Heat pumps operate best in air temperatures above 45°F.

Moreover, it takes significantly longer for this technology to warm the water than a gas heater. That 600-square-foot pool containing 18,000 gallons of water will take about 52 hours to reach 82°F, while a 20-square-foot spa containing 500 gallons of water will take approximately three hours, according to SMUD. This example is based on weather in Sacramento with a 50°F ambient air temperature1.

For 2021, SMUD projected the cost per kW in Sacramento to be $0.35. It takes approximately 6.4kW per hour to heat a pool or spa at a cost of $2.24 per hour (or $0.47 more per hour than gas). To heat a 600-square-foot pool from 50°F to 82°F, it will cost $125 over 52 hours. A spa will cost about $6.75 to heat over three hours.

Heat pumps are more energy-efficient — up to 700%, according to the U.S. Department of Energy. This means that for every unit of electricity used, seven units of heat are generated. Additionally, no greenhouse gasses are emitted under normal operation from heat pump appliances.

Aside from the energy-saving benefits, ease of installation is the primary advantage of heat pumps. While gas heaters require a gas line, heat pumps only require an electric power source. This likely will become a critical selling point if more cities enact building-decarbonization ordinances for new residential and commercial construction. And even in existing structures without a gas line, heat pumps can be installed almost immediately.

The main disadvantage is the length of time required for heat pumps to heat a pool or spa. It will take four to six times as long to heat the water than with a gas heater. This notable difference in heat-up time will likely come as a big shock, especially for consumers who have owned gas-heated spas in the past with a typical heat-up time of 20 minutes, compared to three or more hours with a heat pump.

Heating costs can also add up quickly, depending on electricity rates in one’s city of residence. Unexpectedly high electricity costs can also come as quite a shock when customers receive their electricity bill, especially if they’re used to the lower costs of gas heating.

Other disadvantages of heat pumps include their larger space requirements, reliance on air temperature to determine the BTU output (the cooler the air, the lower the BTUs), and the fact they cannot be installed indoors.

The Key to Success

Decarbonization mandates likely will have a major impact on the industry. Given the legislative trend towards minimizing or eliminating natural gas lines, professionals must be prepared and make sure to clearly advise their customers about all their options for pool heating. The first step is to learn about the mechanics of heat pumps and prepare to pass this information to consumers.

The Pool and Hot Tub Alliance (PHTA) and California Pool and Spa Association (CPSA) have joined forces to stay up to date with decarbonization initiatives including reach codes banning gas lines. For legislative questions, contact John A. Norwood at [email protected].

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