Pool Heat Pump vs Gas Pool Heater: Running Cost

Pool heat pump running costs on the Front Range

A pool heat pump moves heat into water instead of burning fuel. That makes its running-cost comparison different from a gas pool heater or propane pool heater. Strata is taking consultation requests for pool and spa heat pumps now. We quote after a site visit, where we review the pool, electrical capacity, dry-air conditions, and controls.

Gas at $1.00 per therm in an 83% efficient pool heater costs $1.20 per useful therm. At Front Range altitude, gas heater combustion capacity drops roughly 4% per 1,000 ft, or about 20%. A heat pump has no combustion derate, so altitude does not reduce its output through combustion.

A pool heat pump works best for holding water temperature on a planned schedule. It is not a fast, on-demand replacement for every gas heating use. We install and service pool heat pumps and hot tub heat pumps. We do not repair gas pool heaters.

The comparison starts with useful heat, not fuel use alone. Gas loses some input energy through an 83% efficient heater. A heat pump uses electricity to move heat, and its cost changes with COP, air temperature, dry air, and the hour it runs. We use those conditions in a pool heater installation plan.

Heat pump cost by efficiency and conditions

The heat pump figures use Xcel off-peak base rates from the Colorado Public Utilities Commission, then add about 3 cents per kWh of riders. At COP 5 in a warm afternoon, useful heat costs $0.46 at the off-peak base rate and $0.64 with riders. COP describes how much heat the unit moves for the electricity it uses.

At COP 4 in typical conditions, useful heat costs $0.58 at the off-peak base rate and $0.81 with riders. This range is below the $1.20 per useful therm for gas at $1.00 per therm. It shows why water-temperature maintenance during mild daytime conditions favors a pool heat pump.

At COP 3 in cool or very dry air, useful heat costs $0.77 at the off-peak base rate and $1.07 with riders. At COP 2.5 on a 35°F shoulder night, the figures are $0.80 at the base rate and about $1.00 with riders. Cooler and drier conditions narrow the advantage over gas.

These are base rates, not an all-in bill. Riders add about 3 cents per kWh, and a real bill includes charges beyond the base-rate comparison. We check the numbers against your own Xcel bill before we quote. That review prevents a pool heat pump decision based only on a published rate.

Time of use controls shape pool heating cost

According to Colorado Public Utilities Commission Time of Use Rates, Xcel Energy's residential peak is 5 to 9 pm on weekdays. The summer peak rate is 21.3 cents per kWh. Every other hour, including weekends, is off-peak at 7.9 cents per kWh in summer and 6.8 cents October through May.

We heat mostly between 9 am and 5 pm, when the air is warmest and the heat pump is most efficient. The pool then coasts through the 5 to 9 pm peak. With a cover, it loses well under 1°F, and the unit tops up overnight only when needed.

Without time-of-use scheduling, most of the savings disappear. The controls are part of the job, not an add-on. Scheduled to stay off during the peak, a heat pump runs about 10 to 60% cheaper than gas. That schedule also reduces demand during the highest summer electricity rate.

Spa use follows a different pattern. People use spas in the evening, inside the 5 to 9 pm peak. We preheat the spa by 5 pm and let it coast on an insulated cover. A hot tub heater plan needs that timing built into the controls, rather than heating from cold during peak hours.

Propane, gas, and recovery time

At $2.50 per gallon of propane, a heat pump is 2 to 3 times cheaper to run than a propane pool heater. That comparison gives propane-heated pools a strong operating-cost reason to use a pool heat pump for steady temperature maintenance through the swim season.

Gas provides faster recovery after a large temperature drop. Raising a 20,000 gallon pool 10°F takes about 6 hours on a 400,000 BTU gas heater and about 15 hours on a heat pump. A heat pump is for holding temperature, not heating on demand.

This recovery difference belongs in equipment selection. A homeowner who expects a pool to gain 10°F in about 6 hours needs the recovery profile of a 400,000 BTU gas heater. A homeowner who holds the pool near the chosen temperature can use heat pump output across more hours.

Front Range gas equipment also loses about 20% combustion capacity at altitude. That reduction follows the rough 4% drop per 1,000 ft. A heat pump does not have this combustion derate. Its output instead depends on air conditions, which is why dry-air sizing matters.

Dry air, cold weather, and electrical design

Pool heat pump ratings assume 80°F air at 80% humidity. Front Range summer afternoons run 15 to 25% humidity. Real output is lower in this dry air, so we size equipment for dry air instead of using a published rating from warm, humid conditions.

Many standard models stop at 40°F and lose output below 50°F. Cold-climate inverter models with reverse-cycle defrost are rated to run down to 23°F, 5°F or, for some models, -4°F. A cold-climate unit stretches the swim season to roughly April through October and can heat a spa year-round.

A 140,000 BTU pool heat pump needs a 50 A, 240 V circuit. We check panel capacity at the site visit and plan load management where the panel is tight. Electrical capacity is part of the design, because the unit and its controls need the planned circuit before operation begins.

A pool over 20,000 gallons may need two units and two circuits. That requirement affects output planning, panel capacity, and controls. We review the pool volume before quoting so a large pool is not assigned one unit and one circuit when the design needs two of each.

Boulder rules and a consultation request

Boulder County's Swimming Pools, Spas and Hot Tubs code says heated pools of 200 sq ft or more must use solar thermal or non-fossil heating, or offset their energy with on-site renewables. Spas must be offset unless they are CEC Title 20 listed and under 64 sq ft.

The City of Boulder Renewable Energy Offset Requirements Form requires pool and spa energy to be offset with on-site renewables. Heat pumps count on the city offset worksheet for seasonal pools. We confirm with the city how the worksheet credits your heat pump before you apply. Boulder rules accept solar thermal or a renewable offset.

These rules make energy compliance part of the equipment choice. A seasonal pool heat pump has a stated place on the City of Boulder worksheet. A spa has its own offset requirement unless it is CEC Title 20 listed and under 64 sq ft. We review the applicable rule during the site visit.

There is no pool heat pump rebate. A consultation request starts the process. We visit, size the unit for dry air and quote. Pool heat pumps are not in the online estimate. The visit also confirms circuit needs, pool volume, cover use, recovery expectations, and the schedule that drives running cost.

Pool heat pumps by location

Questions we hear

How does a pool heat pump compare with a gas pool heater?

Gas at $1.00 per therm in an 83% efficient pool heater costs $1.20 per useful therm. A heat pump ranges from $0.46 at COP 5 on off-peak base rates to about $1.00 at COP 2.5 on a 35°F shoulder night with riders. Gas recovers temperature faster. Raising a 20,000 gallon pool 10°F takes about 6 hours on a 400,000 BTU gas heater and about 15 hours on a heat pump.

Why does the time of day matter for an electric pool heater?

Xcel's residential summer peak runs from 5 to 9 pm on weekdays at 21.3 cents per kWh. Off-peak electricity is 7.9 cents per kWh in summer and 6.8 cents October through May. We heat mostly from 9 am to 5 pm, then let a covered pool coast through the peak. Without time-of-use scheduling, most savings disappear.

Will a pool heat pump work in dry Front Range air?

Yes, but sizing must account for dry air. Published ratings assume 80°F air at 80% humidity, while Front Range summer afternoons run 15 to 25% humidity. This lowers real output. Standard models stop at 40°F and lose output below 50°F. Cold-climate inverter models with reverse-cycle defrost are rated down to 23°F, 5°F or, for some models, -4°F.

Is a heat pump cheaper than a propane pool heater?

At $2.50 per gallon of propane, a heat pump is 2 to 3 times cheaper to run than a propane pool heater. The comparison depends on maintaining pool temperature during off-peak hours. It does not provide gas-speed recovery after a large temperature drop. We check electrical capacity, pool volume, dry-air output, and your actual Xcel bill before we quote.

What Boulder requirements apply to pool and spa heat pumps?

Boulder County requires heated pools of 200 sq ft or more to use solar thermal or non-fossil heating, or offset energy with on-site renewables. The City of Boulder requires pool and spa energy offsets with on-site renewables, and heat pumps count on its worksheet for seasonal pools. We confirm how the city credits your heat pump before you apply. Request a consultation and we will visit, size, and quote.

Pool heat pump vs gas and propane pool heaters: what each costs to run