Reviewed by a Certified Pool Technician (CPT)
The Short Answer
The most energy-efficient way to heat a pool is with an electric heat pump paired with a solar cover. Heat pumps pull warmth from the surrounding air instead of generating it through combustion, cutting energy costs by 60–80% compared to gas heating while maintaining consistent water temperature for longer swim seasons. For pool owners in warmer climates, the combination of a heat pump and a good solar cover represents the lowest total cost of pool heating available.
Choosing a pool heater isn't just about upfront cost. It's about what you'll spend every month for the next 10–15 years. The wrong choice can cost you thousands in operating expenses over the life of the equipment. The right choice, matched to your climate, pool size, and usage pattern, delivers a comfortable swim season at the lowest possible total cost.
This guide gives you the real numbers: upfront costs, monthly operating costs, payback timelines, and which option wins in which climate.
Pool Heater Cost Comparison: Gas vs. Solar vs. Heat Pump
Understanding the total cost of ownership, not just the purchase price, is what makes this decision clear.
Upfront Cost Comparison
|
Heater Type |
Equipment Cost |
Installation Cost |
Total Upfront |
|
Gas heater (natural gas) |
800–2,500 |
300–800 |
1,100–3,300 |
|
Propane heater |
800–2,500 |
300–800 |
1,100–3,300 |
|
Solar heating system |
2,000–6,000 |
500–1,500 |
2,500–7,500 |
|
Electric heat pump |
1,500–4,000 |
300–600 |
1,800–4,600 |
Annual Operating Cost Comparison
Assumes 20,000-gallon pool, 6-month heating season in a temperate climate, maintaining 82°F water temperature.
|
Heater Type |
Energy Source |
Efficiency |
Annual Operating Cost |
|
Natural gas heater |
$1.50/therm |
~80% |
800–1,800 |
|
Propane heater |
$3.50/gallon |
~80% |
1,500–3,500 |
|
Solar heating |
Free (sun) |
Passive |
0–200 (pump costs) |
|
Electric heat pump |
$0.14/kWh |
COP 5.0–6.4 |
300–600 |
Per U.S. Department of Energy benchmarks: electric heat pumps are 3–5× more energy-efficient than gas heaters for pool heating, delivering 5–6 units of heat energy per unit of electricity consumed.
10-Year Total Cost of Ownership
|
Heater Type |
10-Year Energy Cost |
Equipment (2 replacements gas, 1 heat pump) |
10-Year Total |
|
Natural gas |
8,000–18,000 |
1,600–5,000 |
9,600–23,000 |
|
Electric heat pump |
3,000–6,000 |
1,500–4,000 |
4,500–10,000 |
|
Solar |
0–2,000 |
2,000–6,000 |
2,000–8,000 |
The 10-year comparison is where heat pumps make their strongest case against gas. The higher upfront cost is typically recovered in 2–3 years through energy savings, after which the heat pump delivers 7–12 more years of lower-cost operation.
How Much Does It Cost Per Month to Heat a Pool?
Monthly costs are what pool owners feel most directly, and they vary significantly by heater type, climate, and pool size.
Monthly Cost Estimates by Heater Type and Pool Size
Based on a 5-month active heating season. Assumes maintaining pool at 82°F. Climate: temperate (average ambient 65–75°F during season). Energy rates: $0.14/kWh electricity, $1.50/therm natural gas.
|
Pool Size |
Gas Heater (monthly) |
Heat Pump (monthly) |
Monthly Savings with Heat Pump |
|
10,000 gallons |
80–150 |
25–50 |
55–100/month |
|
15,000 gallons |
120–200 |
40–70 |
80–130/month |
|
20,000 gallons |
150–300 |
50–100 |
100–200/month |
|
30,000 gallons |
200–400 |
70–150 |
130–250/month |
Estimates based on DOE pool heating guidelines. Your actual cost depends on local energy rates, ambient temperature, cover use, and desired pool temperature.
Effect of a solar cover on monthly costs: A good solar cover reduces overnight heat loss by 50–70%, cutting required heating energy by 30–50%. On a $100/month gas heating bill, a solar cover can reduce monthly costs to 50–70 even without changing the heater.
Best Pool Heating Option by Climate
One size doesn't fit all climates. The right heater depends on where you live and how long your swim season is.
Warm Climate (Southern Florida, Southern California, Gulf Coast, Hawaii)
Best option: Electric heat pump
Heat pumps operate most efficiently when ambient temperatures are consistently above 65°F, which describes most of the year in warm climates. Pool owners in these regions can heat 10–12 months annually. The long season maximizes the value of the heat pump's operating cost advantage over gas.
Cost advantage: At 10 months of heating versus 6 months for a temperate-climate pool, the gas-vs-heat-pump annual savings can reach 1,200–3,000 per year on a mid-size pool. Payback period: 1–2 years.
Temperate Climate (Southeast, Mid-Atlantic, Pacific Northwest, Inland California)
Best option: Electric heat pump (with solar cover for shoulder-season extension)
Heat pumps work excellently April through October in these regions. The spring and fall shoulder months (when ambient temps are 55–65°F) are where a heat pump's efficiency drops but still outperforms gas. A solar cover extends the viable swim season by 3–4 weeks at both ends.
Payback period: 2–3 years against gas.
Cool/Northern Climate (Northeast, Midwest, Mountain States)
Best option: Heat pump for the 4–5 month core season; consider gas for rapid heating
Heat pumps function well June through August in most northern climates. April, May, September, and October are marginal; ambient temps may fall below the heat pump's 50–55°F minimum operating threshold. Options:
-
Heat pump for core season only (June–August): Lowest operating cost during the warm months; close the pool for the shoulder months
-
Gas heater for year-round or shoulder-season use: Gas heaters work at any ambient temperature, making them the only practical option for pools that need to heat when ambient temps are below 50°F
-
Combination system: Gas heater for rapid heating and cold-weather supplemental use; heat pump for daily maintenance heating during warm months
Sunny Climate with Low Humidity (Desert Southwest)
Best option: Solar heating + heat pump or solar heating alone
Direct solar exposure is the cheapest energy source available for pool heating. A solar system (roof panels or pool-specific solar mats) paired with a heat pump for cloudy days and nighttime temperature maintenance represents the lowest possible operating cost in sunny climates.
How Long Does a Pool Heat Pump Take to Pay for Itself?
The payback calculation is straightforward: upfront cost premium over gas ÷ annual savings.
Example calculation (20,000-gallon pool, temperate climate):
-
Gas heater total upfront: $1,800 (equipment + install)
-
Heat pump total upfront: $3,200 (equipment + install)
-
Additional upfront cost of heat pump: $1,400
Annual heating costs:
-
Gas heater: $1,200/year
-
Heat pump: $450/year
-
Annual savings: $750/year
Payback period: $1,400 ÷ $750 = 1.9 years
After the payback period, the heat pump delivers lower-cost heating for the remaining 8–12 years of its service life, typically 6,000–9,000 in cumulative additional savings compared to gas over the full equipment life.
ENERGY STAR rebates: Many ENERGY STAR-certified heat pumps qualify for utility rebates of 50–500+ depending on your utility and state. These rebates reduce the effective upfront cost and shorten the payback period.
Factors that accelerate payback:
-
Longer swim seasons (more months of savings)
-
Higher local gas rates (more savings per month)
-
Lower local electricity rates (lower heat pump operating cost)
-
Solar cover use (reduces energy needed from both heater types, but reduces gas costs less proportionally)
Heat Pump Sizing Chart by Pool Size
A correctly sized heat pump is essential, both for performance and for payback calculation accuracy. Undersized units run constantly and never reach target temperature; oversized units cost more without proportional benefit.
BTU Formula
Pool Gallons × 8.34 × Desired Temperature Rise ÷ 24 = BTU/hour required
Example: 20,000-gallon pool, 15°F temperature rise: 20,000 × 8.34 × 15 ÷ 24 = 104,250 BTU/hour minimum
BTU Sizing Chart
|
Pool Volume |
Temperate Climate |
Cool Climate |
Warm/Southern Climate |
|
Up to 10,000 gal |
50,000–65,000 BTU |
65,000–80,000 BTU |
50,000 BTU |
|
10,000–15,000 gal |
65,000–80,000 BTU |
80,000–95,000 BTU |
65,000 BTU |
|
15,000–25,000 gal |
90,000–110,000 BTU |
110,000–125,000 BTU |
80,000–95,000 BTU |
|
25,000–35,000 gal |
110,000–125,000 BTU |
125,000–137,000 BTU |
110,000 BTU |
|
35,000–45,000 gal |
125,000–137,000 BTU |
137,000+ BTU |
125,000 BTU |
AHRI-rated BTU output is measured at 80°F ambient air. At lower ambient temperatures (60–65°F), actual output is 30–40% lower than the rated figure. Size for your actual expected operating conditions, not the test-condition rating.
Climate adjustment: Size up 15–25% for cool climates where ambient temperatures regularly fall below 65°F during the swim season.
Browse our full heat pump collection to compare models by BTU output and pool size.
The Solar Cover Multiplier Effect
No pool heating guide is complete without emphasizing the solar cover; it's not an optional accessory for an efficient heating setup; it's a multiplier.
What a solar cover does:
-
Reduces overnight heat loss by 50–70%
-
Prevents evaporation (evaporation is the largest source of pool heat loss, 50–70% of total heat lost from a typical outdoor pool)
-
Passively adds 10–15°F of solar heating during daylight hours in direct sun
Effect on heating costs with a cover vs. without: A heat pump maintaining an 82°F pool without a cover in temperate conditions needs to replace 4–7°F of heat loss every day. With a solar cover, that loss drops to 1–2°F per day, meaning the heat pump runs far fewer hours and costs far less to operate.
At $100/month heat pump operating cost without a cover, consistent solar cover use often reduces that to 50–70/month, an additional 30–50 monthly savings on top of whatever you're already saving versus gas.
A quality solar cover typically costs 50–200 for a residential pool and pays for itself in energy savings within the first season.
Circulation Matters: The Pump Behind the Heater
Your heater can only heat water that's moving through the circulation system. An undersized or underperforming pump delivers less water to the heat exchanger per hour,, meaning longer heating times, higher energy costs, and uneven temperature distribution.
For pool heating to work efficiently, the pool pump must provide adequate daily water turnover, at minimum, one full pool volume through the system every 8 hours. For a 20,000-gallon pool, that's at minimum 42 GPM.
A variable-speed pump programmed to run at higher RPM during active heating cycles and lower RPM during maintenance filtration optimizes both heating efficiency and energy cost. For guidance on optimal pump runtime for heated pools, see our guide on whether to run a pool pump 24 hours a day.
For protecting your heat pump and associated pool equipment during cold weather, see our pool equipment freeze protection guide.
Frequently Asked Questions
What is the most energy-efficient way to heat a pool?
An electric heat pump paired with a solar cover. Heat pumps deliver 5–6 units of heat energy per unit of electricity consumed, 3–5× more efficient than gas. A solar cover reduces the amount of heat the pump has to generate by preventing 50–70% of overnight heat loss.
How much does it cost per month to heat a pool?
With a gas heater: 80–400/month depending on pool size, local gas rates, and climate. With an electric heat pump: 25–150/month for the same pools. Monthly savings of 55–250 are typical when switching from gas to a heat pump.
What is the cheapest way to heat a pool long-term?
Solar heating has the lowest energy cost ($0 after installation) in climates with adequate sunlight. For climates without reliable sun or for year-round heating, an electric heat pump is the next most cost-effective option. Gas is the most expensive long-term heating choice for pools used regularly.
How long does it take for a pool heat pump to pay for itself?
Typically 1.5–3 years in energy savings versus a gas heater, depending on local energy rates, swim season length, and pool size. After payback, the heat pump delivers 8–12 more years of lower-cost heating compared to gas.
Which pool heater is best for cold climates?
Gas heaters work at any ambient temperature and are the only practical option when ambient temps fall below 50°F. In cool-climate pools with a 4–5 month season, a heat pump for the core summer months combined with gas for shoulder-season use is often the optimal cost approach.
Does a solar cover really reduce heating costs?
Significantly. A solar cover reduces overnight heat loss by 50–70% and eliminates evaporation, which accounts for the majority of pool heat loss. Most pool owners see 30–50% reduction in heating energy costs from consistent cover use, often making the cover the single highest-ROI investment in a pool heating setup.
