Gas vs Electric Pool Heater

The gas vs electric pool heater decision comes down to which energy your property can supply and how you plan to swim. “Electric” covers two very different machines: a heat pump, which uses electricity to pull heat out of the outdoor air, and an electric resistance heater, which turns electricity directly into heat through an element. Pick gas (natural gas or propane) when you want heat on short notice, swim into cool spring and fall weather, or already have a gas line near the equipment pad. Pick a heat pump when you swim most days in a mild or warm climate and your electrical panel can take a large 240-volt circuit. Consider a resistance heater mainly for a spa, a small pool, or an indoor equipment room where a gas heater cannot be vented.

Safety note: gas heaters involve fuel piping, combustion, and exhaust that contains carbon monoxide, and every type of pool heater needs a high-voltage electrical connection. This article compares heater types; it is not installation guidance. Have a licensed gas contractor handle gas or propane piping, a licensed electrician handle circuits and bonding, follow the manual for the exact model, and ask your local building department about permits.

Gas vs Electric Pool Heater at a Glance

The table below compares the three options on the points that decide most installs. Each row is sourced in the sections that follow; purchase price and running cost reflect one heater maker’s comparison of gas and heat pumps, which does not rate resistance heaters.

Factor	Gas heater	Electric heat pump	Electric resistance heater
Energy source	Natural gas or propane	Electricity	Electricity
How it makes heat	Burns fuel; water passes through a heat exchanger	Moves heat from outdoor air into the water	Heats water with electric elements
Main utility needed	Gas line from the meter, or a propane tank	Dedicated 240-volt circuit	Dedicated 240-volt circuit, often large
Also needs	120 or 240 volt power for controls and ignition	Open outdoor air and room for condensation to drain	Adequate water flow before elements switch on
Exhaust	Yes, contains carbon monoxide	None	None
Effect of cold air	Little	Output drops as air cools	Little
Purchase price	Lower	Higher	Not rated in that comparison
Cost to run	Higher	Lower	Not rated in that comparison
Indoor equipment room	Only with the specified vent system	No, outdoor only	Yes, rated for indoor and outdoor use

What “Electric” Means: Heat Pump or Resistance Heater

The phrase “electric pool heater” is used for two different machines, and lumping them together hides the biggest difference in the whole decision. A heat pump and a resistance heater both plug into a 240-volt circuit, but they work on different principles and suit different pools.

A heat pump is a refrigeration machine. Hayward’s heat pump installation and operation manual for in-ground pools rates its units by coefficient of performance (COP), which compares heat delivered with electricity used. The manual lists a COP of 5.7 for most of its 90,000 to 140,000 Btu/hr models with 80°F air, 80% humidity, and 80°F water, and a COP of 4 for every model with 50°F air. In plain terms, under those rated conditions the unit delivers several units of heat for each unit of electricity it draws, because most of the heat comes from the air.

A resistance heater has no compressor and no fan. Raypak’s product page for its E3T single-phase electric pool and spa heater lists a thermal efficiency of 100%, which means essentially all the electricity becomes heat in the water. That is efficient as a conversion, but it is still one unit of heat per unit of electricity, so a resistance heater needs far more electrical capacity than a heat pump to deliver the same heat. In practice, that tends to limit them to spas and small pools.

Gas Pool Heaters: Natural Gas or Propane

A gas heater burns fuel and passes pool water through a heat exchanger. Pentair’s pool heater overview lists its strengths as a lower initial purchase price, optimal performance in all climates, and fast heat-up times, and its trade-offs as a higher cost to operate, large gas consumption, and lower energy efficiency compared to heat pumps. The same page calls gas an ideal choice if you live in an area with access to low-cost natural gas.

Natural gas: check the meter and the pipe run

Having gas service at the house does not mean the pool pad is ready for a heater. The Pentair MasterTemp installation and user’s guide says the required gas pipe size depends on the distance from the gas meter to the heater, and that the meter should be checked to make sure it can supply enough gas to the heater and any other appliances on the same meter. It also sets a supply pressure range for the heater and says the gas supply must follow the applicable fuel gas codes and local codes.

For a house where the furnace, water heater, and range already share the meter, a large pool heater can push the existing service past what it was sized for. A long trench from the meter to a pad at the back of the yard also adds work. Ask the gas contractor to confirm meter capacity and pipe size before you choose a heater model.

Propane: where the tank can go

Pentair’s heater selection guide says units that run on propane tanks are the best option if you cannot connect to underground gas lines. Propane brings its own siting rules. The MasterTemp guide warns of a risk of explosion if the heater is installed near propane storage, notes that propane is heavier than air, and says to locate the heater away from propane storage and filling equipment as the propane storage standard and local fire officials specify. The size and placement of the tank, and how often it is refilled, are questions for your propane supplier and a licensed installer.

A gas heater is built for one fuel. The MasterTemp guide says not to run a heater set up for natural gas on propane or the other way around, and to refer any fuel conversion to a qualified service technician or gas supplier. If you might switch from propane to natural gas later, ask about conversion before you buy.

Gas heaters still need electricity

A modern gas heater is not off the grid. The MasterTemp guide says the heater uses hot-surface ignition instead of a standing pilot and requires an external 120 or 240 volt power source to operate. Budget for an electrician as well as a gas contractor, even if the heater burns gas.

Exhaust and carbon monoxide

Burning fuel creates exhaust, and the MasterTemp guide is direct about it: the exhaust contains toxic levels of carbon monoxide, a gas you cannot see or smell. The guide says never to use the heater in the home or in partly enclosed areas such as garages unless the specified ventilation system is used, to install it far from open windows, doors, and vents when outdoors, and to use the heater with carbon monoxide detectors installed near it. It also says the heater may not be installed within 5 ft of the inside surface of a pool or spa unless a solid fence, wall, or other permanent barrier separates them. Those rules shape where a gas heater can sit on a small lot.

Electric Heat Pumps: Efficient, but Weather Dependent

Heat pumps trade a higher purchase price for lower running costs. Pentair’s overview lists them as highly energy efficient with a lower operational cost, with a higher initial purchase price, and notes that heating performance is related to air temperature and humidity. It describes a heat pump as a superior option if you live in an area with low electricity costs.

The electrical side is substantial. In the Hayward heat pump manual, the 90,000 to 140,000 Btu/hr models run on 240-volt power with recommended breaker sizes of 40 to 50 amps, and the manual calls for an electric disconnect switch within line of sight of the unit and wiring that follows the electrical code requirements for swimming pools and local codes. Older homes with a full panel may need an electrical service review before a heat pump is practical.

Placement matters too. The same manual says not to install the heat pump in a fully enclosed space such as a garage or shed, lists an air operating range of 40 to 115°F, and says the unit performs more efficiently in direct sunlight with ample air intake. Those limits are where a pool heat pump against a gas heater is decided for many owners: cold-weather output and heat-up speed set how long a heat pump can carry your swim season.

Electric Resistance Heaters: Simple, Compact, Power Hungry

A resistance heater is the easiest of the three to place. Raypak’s article on choosing the right pool heater says its E3T electric unit can be installed in smaller spaces or in indoor locations where venting a gas heater is not possible. There is no exhaust, no fuel, and no outdoor air requirement.

The cost of that simplicity is electrical load. The Raypak E3T installation and operation manual covers single-phase models from 5.5 kW to 27 kW, all rated for 240-volt power only. The largest model lists a nominal total draw of 112.5 amps and three 50-amp double-pole breakers, and the manual tells installers to make sure the home has sufficient electrical power for the maximum amperage load before installing. It also requires installation by a licensed and qualified electrician following the electrical code for pools and local codes.

Compare that with the heat pump figures above and the trade-off is clear: the resistance heater draws far more current for its heat output. On a spa that only needs a few degrees before a soak, or a small pool in a pool house, that can be acceptable. On a full-size backyard pool that you want warm all season, it rarely is.

Running Cost and Purchase Price

Exact costs depend on your local gas and electric rates, your climate, the pool size, and how warm you keep the water, so no single answer fits every yard. The pattern from the makers is consistent, though. Hayward’s heater comparison page describes gas heaters as having lower operating costs for intermittent heating and heat pumps as having lower operating costs to maintain temperature. The Pentair overview adds that heat pumps thrive in mild to warm climates where electricity costs are low to moderate, and that gas heaters can be a great option in cooler climates where gas prices are low to moderate.

Put together, the running cost question becomes a question about habits. A pool held at swimming temperature from May through September usually favors a heat pump in a mild climate. A pool heated a dozen weekends a year favors gas, because the heater only burns fuel when you need it. Resistance heaters carry the heaviest electrical load per degree and make the most sense where the volume of water is small. Installation costs vary as much as running costs: a new gas line, a propane tank, or an electrical service upgrade can outweigh the difference in heater price, so get quotes for the hookup along with the heater.

Which Heater Fits Your Backyard

• Gas line already at the pad, weekend or holiday use: Natural gas. You get fast heat on demand, and the fuel line is the hard part already done.
• No gas line, swimming most days in a warm or mild region: A heat pump on a dedicated 240-volt circuit, run with a cover.
• No gas line, cool shoulder seasons, and room for a tank: Propane, sited according to the heater manual and your propane supplier.
• Spa, plunge pool, or very small pool: An electric resistance heater, if your panel can carry the load.
• Equipment indoors or in a pool house: A resistance heater, or a gas heater with the indoor vent system the manual specifies. A heat pump is not an option in an enclosed room.
• Long season plus quick boosts: A heat pump for daily use with a gas heater for cold snaps. Hayward’s comparison page describes this pairing as using the heat pump a majority of the time and switching to gas when the temperature drops.

Once you know which energy source fits, the next step is choosing a pool heater model sized for your water volume and climate. A cover and solar panels reduce how hard any heater has to work, and they belong in the plan for how to heat a pool at a lower running cost.

Who Should Skip Each Type

• Skip gas if you want to hold a warm temperature every day all summer and gas prices are high where you live, if there is nowhere on the property to place the heater away from windows, doors, and propane storage, or if no one in the household wants combustion equipment near the house.
• Skip a heat pump if you swim mostly in cool spring and fall weather, if the only spot for the unit is enclosed or heavily shaded, or if your electrical service cannot support another large 240-volt circuit without an upgrade you do not want.
• Skip a resistance heater for a full-size backyard pool that you heat for weeks at a time. It is not a good fit unless the volume of water is small or the alternatives cannot be installed.

When to Call a Pro

Every heater in this comparison is a job for licensed trades. Call a licensed gas contractor or your gas supplier for meter capacity, gas piping, propane tank placement, and venting. Call a licensed electrician for any new circuit, breaker, disconnect, or bonding work. The Pentair MasterTemp guide, the Hayward heat pump manual, and the Raypak E3T manual all note that some states or jurisdictions require installers to be licensed. If a gas heater smells of gas or exhaust, shut it off and call the gas company or a qualified technician. If any heater trips a breaker repeatedly or shows scorching, turn off its power at the breaker and call for service.

More heater comparisons and guides are collected in the pool heaters section.

FAQ

Is a gas or electric pool heater cheaper to run?

It depends on how you use the pool. Pentair rates heat pumps as having a lower operational cost and gas heaters a higher cost to operate, while Hayward describes gas as cheaper for intermittent heating and heat pumps as cheaper for holding a temperature. Electric resistance heaters draw the most power for the heat they produce. Your local energy rates and swim schedule decide the real answer.

Is an electric pool heater the same as a heat pump?

No. A heat pump uses electricity to move heat from the outdoor air into the water, so its output depends on air temperature. A resistance heater turns electricity directly into heat with elements and works regardless of air temperature, but it needs much more electrical capacity for the same output.

Does a gas pool heater need electricity?

Yes, for many current models. The Pentair MasterTemp guide says the heater requires an external 120 or 240 volt power source for its controls and hot-surface ignition. Plan for an electrical connection along with the gas line.

Can a natural gas pool heater run on propane?

Not as delivered. The MasterTemp guide says to use the heater only with the fuel it is designed for and to refer any fuel conversion to a qualified service technician or gas supplier. Check the rating plate for the fuel type before installation.

What size breaker does an electric pool heater need?

It varies by model, so follow the manual and a licensed electrician. As examples, the Hayward heat pump manual lists recommended breakers of 40 to 50 amps for its 90,000 to 140,000 Btu/hr models, and the Raypak E3T manual lists one 30-amp breaker for its 5.5 kW model and three 50-amp breakers for its 27 kW model.

About the author