Pool Heat Pump vs Gas Heater: Costs, Efficiency, Sizing, and Climate Guide

Trying to decide between a pool heat pump and a gas heater? This guide compares performance, costs, and practicality for U.S. homeowners. It explains how each system works, what it costs to buy and run, how fast each heats, and which climates favor each option—so the pool stays warm without burning cash.

Meta Description: Compare pool heat pump vs gas heater on cost, efficiency, speed, climate, and sizing to choose the best pool heater for your home.

How Pool Heat Pumps And Gas Heaters Work

Pool Heat Pumps

A pool heat pump moves heat from outdoor air into pool water using a refrigeration cycle, similar to an air conditioner in reverse. Because it moves heat rather than creating it, it can deliver more heat energy than the electricity it consumes.

Efficiency is expressed as Coefficient of Performance (COP). A COP of 5 means 1 kWh of electricity delivers 5 kWh-equivalent of heat. At around 80°F air temperature, many modern pool heat pumps reach COP 5–6. As air temperature drops toward 50–60°F, COP typically falls to 3–4 and heating output declines.

Best use case: Maintaining a steady pool temperature for long periods in mild-to-warm climates, especially with a solar cover to reduce heat loss.

Gas Pool Heaters (Natural Gas And Propane)

Gas heaters burn natural gas or propane to heat water as it passes through a heat exchanger. They provide high, predictable heat output regardless of outdoor air temperature, making them excellent for quick warm-ups or cold mornings.

Efficiency is thermal efficiency (percent of fuel energy turned into heat). Standard units are typically 82–84% efficient; some condensing, low-NOx models reach 90–95% but cost more and have specific venting requirements.

Best use case: Rapid heating and intermittent use, such as weekend-only swimming or colder climates where air temperatures often fall below heat pump sweet spots.

Cost Breakdown: Purchase, Installation, And Operating

Upfront and ongoing costs vary by region, energy prices, and equipment size. The figures below reflect common U.S. ranges.

Typical U.S. energy prices for comparison: electricity ~$0.16/kWh; natural gas ~$1.20/therm; propane ~$3.00/gallon. Local rates vary significantly; adjust the math for your bill.

Operating Cost Per Million BTU Of Heat Delivered

Use these benchmarks to compare energy costs. 1 MMBtu ≈ 293 kWh of electric resistance heat.

Key takeaway: At typical U.S. rates, a heat pump usually costs less per unit of heat than natural gas, and far less than propane—especially in warmer air where COP is higher.

Heating Speed, Real-World Scenarios, And Time-To-Temperature

How fast the pool warms depends on heater output, pool size, desired temperature rise, and heat losses from wind and evaporation.

Quick Math To Estimate Heat Needed

It takes ~8.34 BTU to raise 1 gallon of water by 1°F. Total BTU needed = Pool gallons × 8.34 × Desired °F rise.

• Example: 20,000-gallon pool, 10°F rise → 20,000 × 8.34 × 10 = 1,668,000 BTU (≈1.67 MMBtu).

Time-To-Heat Comparison (Idealized)

The table assumes consistent output; heat pump output falls in cool air, and covers reduce losses substantially.

What this means: Gas is faster for big temperature jumps. Heat pumps are cheaper to run, especially if run continuously to maintain temperature with a cover, rather than chasing large day-of swims.

Climate And Seasonal Fit

Climate has an outsized impact on the “Pool Heat Pump vs Gas Heater” decision. Heat pump efficiency and output drop in cooler air, while gas heaters perform consistently across temperatures.

Where Heat Pumps Shine

• Warm-to-mild climates: Florida, Gulf Coast, Southern California, and much of the Southeast and Mid-Atlantic during pool season.
• Long seasons, daily use: Best when maintaining temperature for months, not just weekends.
• With a solar cover: Reduces evaporation and heat loss by 50–70%, making heat pumps dramatically more effective.

Where Gas Heaters Win

• Cold nights or shoulder seasons: Need rapid morning warm-ups when air is 50–60°F.
• Intermittent use: Weekend homes, occasional parties, or spas needing fast recovery.
• Very windy sites: Evaporation losses dominate; rapid-output gas can overcome losses quickly.

Pro tip: Even in warm states, a gas heater is ideal for a spa attached to a pool because of the required rapid temperature rise.

Environmental Impact

Emissions vary widely by fuel and efficiency. Using U.S. average grid emissions, heat pumps tend to have the lowest CO₂ per unit of heat delivered.

Bottom line: In most regions, a heat pump delivers the lowest emissions per unit of pool heat, particularly with a solar cover and daytime operation.

Sizing Your Pool Heater Correctly

Right sizing depends on how quickly the pool needs to warm and how much temperature you maintain daily. Oversizing can shorten run time; undersizing can make target temperatures unattainable in wind or cool spells.

Simple Sizing Method

1. Find pool volume: Gallons = Length × Width × Average Depth × 7.5.
2. Choose desired temperature rise per hour: For quick heat, 1–2°F/hr; for maintenance, 0.25–0.5°F/hr is fine.
3. Calculate BTU/hr needed: Gallons × 8.34 × °F rise per hour.
4. Pick a heater: Choose a gas heater whose output meets or exceeds this BTU/hr. For a heat pump, remember real output falls in cool air; size accordingly or plan for longer run times.

Example: 20,000 gallons; want 10°F rise in 8 hours → BTU/hr = 20,000 × 8.34 × (10/8) ≈ 208,500 BTU/hr. A 300k BTU gas heater (≈250k output) meets this. A 120k BTU heat pump will take roughly twice as long in warm air and longer in cool air.

Rule of thumb: For typical residential pools (12,000–25,000 gallons), heat pumps of 95k–140k BTU and gas heaters of 250k–400k BTU are common. Wind exposure and cover usage can change these recommendations significantly.

Installation Considerations

Heat Pumps

• Electrical: Usually 240V with a dedicated 30–60A breaker (check nameplate). Professional wiring is required.
• Airflow: Needs several feet of clearance around the unit and above for intake/exhaust air. Avoid tight corners and recirculation.
• Drainage: Condensate water can be substantial; plan for safe drainage.
• Location: Place away from bedrooms or neighbors to minimize perceived fan noise.

Gas Heaters

• Gas supply: Properly sized gas line and regulator are critical. Long runs or undersized pipes cause low manifold pressure and poor performance.
• Vent and clearances: Outdoor units require clearances around exhaust; indoor installations need approved venting. Check local code and manufacturer instructions.
• Permits and emissions: Some air quality districts require low-NOx models; permits may be required for gas line work.

Tip: Both heater types should be installed on a stable pad with unions for service and with adequate straight pipe runs to satisfy flow sensors.

Maintenance, Reliability, And Lifespan

Both heater types benefit from annual checkups and consistent water chemistry. Poor chemistry is a leading cause of premature failure.

• Heat pumps: Clean evaporator coils and filters; keep leaves and debris away; verify fan spins freely; inspect electrical connections; ensure correct water flow. Typical lifespan is 10–15 years.
• Gas heaters: Inspect burners and heat exchanger for soot or scale; verify proper gas pressure; ensure unobstructed exhaust; check igniters/sensors. Typical lifespan is 7–12 years.
• Water chemistry: Maintain pH, alkalinity, calcium hardness, and sanitizer within ranges. Salt systems can accelerate corrosion if chemistry is neglected; titanium heat pump exchangers resist corrosion but are not immune to abuse.

Warranties: Many heat pumps offer 2–5 years parts and longer coverage on the titanium exchanger; gas heaters often offer 1–3 years with extended options. Read warranty conditions—improper chemistry can void coverage.

Noise And User Experience

Heat pumps use a fan and compressor, producing sound levels often in the 50–65 dB range at a few feet—similar to a quiet conversation to a box fan, depending on model. Variable-speed “inverter” heat pumps can be quieter at partial load.

Gas pool heaters have blower and combustion noise, but because they often run for shorter bursts, perceived noise can be lower. Placement matters: Keep any heater away from bedroom windows and property lines when possible.

Usage Strategies To Cut Costs

• Solar cover or liquid solar blanket: Evaporation is the largest heat loss. A cover can reduce heat loss by 50–70%, slashing energy use and making heat pumps far more effective.
• Run heat pumps during warmer daytime hours: Higher air temperatures boost COP and speed.
• Lower setpoint when not swimming: Even a 2–4°F setback saves energy; don’t let the pool drop so far that recovery becomes expensive.
• Windbreaks: Fences or hedges reduce evaporative loss, improving comfort and cutting energy use.
• Filter run time coordination: Heaters only run with adequate flow; align pump schedules with heating windows.

Incentives, Codes, And Availability

Some utilities and states offer rebates for high-efficiency pool heat pumps. Gas heater rebates are less common. Low-NOx gas models may be required in parts of California and other air-quality districts.

Check local codes and programs: Electrical work may require permits; gas line modifications often do. Utility marketplaces sometimes provide instant rebates on qualifying heat pumps.

Return On Investment: Examples

Payback depends on climate, run time, and energy prices. Two illustrative scenarios highlight the differences.

Scenario A: Warm Climate, Long Season (Electricity $0.14/kWh, Gas $1.50/therm)

• Heat pump COP 5 → ~$8.20/MMBtu; natural gas 84% → ~$17.90/MMBtu.
• Savings: ~$9.70/MMBtu with heat pump.
• Seasonal usage 50 MMBtu → ~$485 saved per season.
• Upfront difference $2,000 more for heat pump → ~4-year payback.

Scenario B: Cooler Climate, Intermittent Use (Electricity $0.20/kWh, Gas $1.10/therm)

• Heat pump COP 3–4 → $14.70–$19.50/MMBtu; natural gas 84% → ~$13.10/MMBtu.
• Gas often cheaper per MMBtu and heats faster for occasional weekends.
• Smaller seasonal run time reduces potential savings from a heat pump.

Takeaway: The more hours the heater runs in warm air, the stronger the heat pump’s economic case. For sporadic, fast heating in variable weather, gas often wins on convenience and total cost.

Common Misconceptions

• “Heat pumps don’t work below 60°F.” Many operate into the 40s, but output and COP drop. They’re still useful for maintaining temps, especially with covers; they’re just slower.
• “Gas is always cheaper.” Not when electricity is modestly priced and air is warm. In many states, heat pumps beat gas on operating cost.
• “Bigger is always better.” Oversizing can short-cycle gas units and add cost. Size for desired heat-up speed and climate; use a cover to control losses.

Heat Pump Technology Trends

• Inverter variable-speed compressors: Better part-load efficiency, quieter operation, and steadier water temperature.
• Colder-climate performance improvements: Enhanced coils and refrigerants extend operation to lower ambient temperatures with higher COP.
• Smart controls: App integration, scheduling, and diagnostics improve user experience and efficiency.

Gas Heater Developments

• Higher efficiency and low-NOx designs: Improved heat exchangers and controls reduce emissions and fuel use.
• Durable materials: Cupro-nickel and other alloys resist corrosion in aggressive water, extending life under proper chemistry.

Safety And Reliability Considerations

• Combustion safety (gas): Ensure correct venting and clearances. Never enclose an outdoor-only heater. Annual inspection reduces CO and fire risks.
• Electrical safety (heat pumps): Use a dedicated circuit, correct breaker size, and proper bonding/grounding.
• Freeze protection: Many heaters have built-in freeze protection. In freezing climates, winterize plumbing or run freeze-protect mode as directed.

Hybrid And Alternative Approaches

• Solar thermal + heat pump: Solar handles base load; heat pump trims and covers cloudy spells. Very low operating cost with proper cover use.
• Solar cover + gas heater: For weekend use, the cover cuts losses so gas can quickly lift temperature without fighting nightly evaporation.
• Dedicated spa heater (gas) + pool heat pump: Use each technology where it excels—fast spa recovery and efficient pool maintenance.

Quick Decision Guide

Operating Tips By Heater Type

Heat Pump Best Practices

• Run during warmer daytime hours to maximize COP; maintain setpoint rather than deep setbacks.
• Use a solar cover nightly to retain heat, reduce evaporation, and shorten run time.
• Keep the coil clean and maintain clear airflow for peak performance.

Gas Heater Best Practices

• Heat with the cover on to cut losses during warm-up; uncover for swimming.
• Annual service for burners and heat exchanger to keep efficiency up and reduce soot.
• Verify gas line sizing if experiencing slow heating or frequent ignition faults.

Frequently Asked Questions

What Size Heater Is Best For A 15,000–20,000 Gallon Pool?

Common choices are a 95k–120k BTU heat pump or a 250k–300k BTU gas heater. If fast warm-ups are needed, lean larger on gas. If maintaining temperature in a warm climate with a cover, a 95k–120k BTU heat pump is often sufficient.

Do Heat Pumps Work At Night?

Yes, but they are more efficient in warmer daytime air. If possible, schedule most heat pump run time during the day and let the cover prevent overnight losses.

Is Propane A Good Choice?

Propane works well technically but is almost always the most expensive fuel per MMBtu. If natural gas is unavailable, a heat pump typically has lower operating costs than propane in mild climates.

Can I Use Both A Heat Pump And A Gas Heater?

Yes. Many owners use a heat pump to maintain pool temperature and a gas heater for rapid spa heating or occasional quick boosts. This hybrid approach balances cost and convenience.

How Important Is A Solar Cover?

Extremely. Covers reduce evaporation—the largest source of heat loss—by 50–70%. They pay for themselves quickly by cutting energy costs and improving heater performance.

What To Check Before Buying

• Energy rates: Compare your actual $/kWh, $/therm, or $/gal to the tables above.
• Climate and schedule: Daily users in warm areas favor heat pumps; sporadic/cold-weather use favors gas.
• Electrical or gas availability: Ensure adequate panel capacity for a heat pump or properly sized gas line for a heater.
• Space and noise: Confirm clearances and place units to minimize sound and exhaust impacts.
• Cover plan: Budget for and commit to using a solar cover to control costs with either heater type.

Sample Specification Checklist

• Heat Pump: BTU rating at 80°F air/80°F water/80% RH; minimum operating temperature; COP at multiple ambients; inverter vs fixed-speed; titanium heat exchanger; noise rating (dB); electrical amperage; warranty terms.
• Gas Heater: Input BTU; thermal efficiency; low-NOx certification if required; cupro-nickel exchanger; venting and clearance requirements; gas line size; ignition type; warranty terms.

Final thought: In the “Pool Heat Pump vs Gas Heater” choice, align equipment with climate and usage. Heat pumps excel at efficient, steady warmth in mild weather with a cover. Gas delivers speed and reliability for quick heat-ups and cold mornings. Matching technology to the way the pool is used is the surest path to comfortable, affordable swimming.