Pool heater recommendations are one of the highest-stakes conversations a service operator has with a customer. A bad heater pick costs the customer $200 to $500 per month in operating costs they did not budget for. A good heater pick saves them $1,500 to $3,000 per year over the wrong alternative. This is the operator reference for the three pool heater technologies in 2026: gas (natural and propane), heat pump, and electric resistance. What each costs to buy, what each costs to run, and which one to recommend by climate and use case.
TL;DR
- Gas heaters: highest BTU output, fastest heat-up, COP 0.85 to 0.95. $1,500 to $4,000 hardware plus install
- Heat pumps: highest efficiency, COP 3.0 to 7.0. $2,000 to $6,000 hardware plus install. Slow heat-up
- Electric resistance: COP exactly 1.0. Cheapest hardware but highest operating cost. Rare in residential
- Operating cost per month: $200 to $500 for gas, $50 to $150 for heat pump, $300 to $700 for electric resistance
- Heat pumps work efficiently above 50F ambient air; gas wins in cooler climates and intermittent use
- Most year-round residential customers in sunbelt markets should choose heat pump; vacation home and seasonal customers should choose gas
The 3 pool heater technologies
Pool heating in residential service comes down to three technologies. Gas combustion (natural gas or propane), heat pump (extracts heat from ambient air), and electric resistance (heating elements, same principle as a hot water heater). Each has a fundamentally different efficiency profile, which translates directly to monthly operating cost.
The single number that distinguishes them is COP (coefficient of performance), the ratio of heat delivered to energy consumed. Gas heaters run a COP of 0.85 to 0.95. Heat pumps run a COP of 3.0 to 7.0. Electric resistance is exactly 1.0. That spread is the entire story.
Gas heaters: the workhorse
Gas heaters burn natural gas or propane to heat pool water through a copper or cupronickel heat exchanger. Standard residential output is 200,000 to 400,000 BTU per hour, which heats a 15,000 gallon pool from 70F to 85F in roughly 8 to 14 hours. Fast heat-up is the gas heater's biggest advantage. A customer who wants to heat the pool for a weekend gets the pool warm in a few hours with gas; with a heat pump the same job takes 2 to 3 days.
Hardware cost: $1,500 to $4,000 for the heater itself. Installation: $500 to $1,500 with existing gas line, $1,500 to $3,500 if a new gas line needs to be run.
Operating cost depends on natural gas vs propane rates in the local market. Natural gas is typically $1 to $2 per therm, propane is $2 to $4 per gallon. Monthly heating cost for a residential pool: $200 to $500 in moderate climates, more in cold ones.
Heat pumps: the efficiency play
A pool heat pump works the same way a home air conditioner does, in reverse. A compressor extracts heat from ambient air and transfers it to the pool water. Because the system is moving heat rather than generating it, COP is 3.0 to 7.0, meaning each unit of electricity delivers 3 to 7 units of heat.
Hardware cost: $2,000 to $6,000. Installation: $300 to $800. Total turnkey: $2,500 to $7,000.
Operating cost is the best in pool heating. Monthly cost for a residential pool with a heat pump: $50 to $150. Annual savings over a gas heater: $1,500 to $3,500.
The trade-off: heat pumps work efficiently above 50F ambient air. Below 50F, COP drops sharply, and below 40F most heat pumps shut down completely. Heat pumps also take 24 to 72 hours to bring a cold pool up to swim temperature. For a customer who wants warm water on demand, gas wins.
“Heat pumps work best when you do not need to heat the pool. Set it and forget it.”
Electric resistance: rare and usually wrong
Electric resistance heaters use heating elements similar to a tank water heater. COP is exactly 1.0. Hardware is cheap ($500 to $1,500), but operating cost is the highest of any heating option, typically $300 to $700 per month for residential. They are rarely the right choice for a residential pool.
The exception: very small pools (under 6,000 gallons) where the absolute fuel volume is small, or pools where running new gas line is prohibitively expensive and a heat pump cannot install (insufficient space, HOA restrictions). In commercial pool service, electric resistance is sometimes used for spas because heat-up time is fast and gas line tie-ins are restricted.
Climate fit
The single biggest variable in pool heater recommendation is local climate.
- Sunbelt year-round swim (Phoenix, South Florida, San Diego, Houston): heat pump wins on operating cost; ambient air rarely drops below 50F
- Sunbelt seasonal (Las Vegas, Austin): heat pump for season extension, gas only if customer wants to swim Dec-Feb
- Mixed climate (Atlanta, Charlotte, central California): heat pump for shoulder seasons, gas as supplemental for cold snaps
- Cold climate (Northeast, Midwest): gas only. Heat pump cannot perform below 50F ambient
- Mountain markets (Denver, Salt Lake City): gas for swim season heating, pool gets closed in winter
Use case fit
Beyond climate, the customer's use pattern drives the recommendation. A daily swimmer who keeps the pool at 84F year round is the perfect heat pump customer. The pump runs continuously at low duty cycle and operating cost is minimized.
A weekend or vacation home customer who wants to heat the pool for a single weekend twice a month is the wrong heat pump customer. The heat pump cannot bring the pool up fast enough. They need gas.
A customer with a spa who wants instant hot water on demand also needs gas. Heat pumps are not fast enough for spa use.
Sizing the heater
Heater sizing is BTU per hour. Standard residential rule: 50,000 BTU per 10,000 gallons of pool water for moderate climates, doubled for cold-snap climates. A 20,000 gallon pool in Phoenix is fine with a 200,000 BTU heater. A 20,000 gallon pool in Boston needs 400,000 BTU.
Heat pumps are sized similarly but the BTU rating is usually given alongside a temperature rating (e.g., 110,000 BTU at 80F ambient). Service operators selecting a heat pump should pick a size where the BTU rating at the customer's coldest expected ambient air temperature is still adequate.
Service operator pricing for heater installs
- Gas heater swap (existing gas line): $1,500 to $4,000 hardware plus $500 to $1,500 labor
- Gas heater swap with new gas line: add $1,000 to $3,000 for gas line work
- Heat pump install: $2,000 to $6,000 hardware plus $400 to $1,000 labor
- Pool heater service call (no parts): $150 to $300 diagnostic
- Heat exchanger replacement (gas heater): $400 to $900 parts plus 2 hours labor
Common heater recommendation mistakes
- Recommending heat pump in a cold climate. Customer cannot heat the pool below 50F ambient and switches operator
- Recommending gas to a year-round sunbelt customer. Customer pays 3x more in operating cost than necessary
- Undersizing the heater. Pool takes 24+ hours to heat for a weekend party and customer blames the operator
- Not checking the customer's gas service capacity. New 400K BTU heater on a undersized gas line starves for fuel
- Skipping the heat exchanger cleaning on annual maintenance. Heater efficiency drops 15 to 25% with mineral buildup
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