How to Keep Your Pool Warm Without Running Up Your Electric Bill

What a pool heater does and why you might need one

A pool heater raises the temperature of your pool water so you can swim comfortably outside the warmest months of the year. Most pools without a heater sit between 65 and 75 degrees Fahrenheit depending on the season and your location—cold enough that most people won't stay in long. A heater can bring that up to 78 to 82 degrees, which is the range most swimmers find comfortable.

You don't need a heater to own a pool, but you do need one if you want to use your pool during spring, fall, or winter, or if you live somewhere the water never naturally warms up enough for regular swimming. The type of heater that makes sense depends on your pool size, your climate, how often you use the pool, and how much you want to spend on fuel or electricity each month.

Key Takeaways

• Gas heaters heat water quickly but cost more to run month-to-month than heat pumps or solar heaters.
• Heat pumps are efficient in warm climates but slow to heat and stop working well when outdoor air drops below 50 degrees Fahrenheit.
• Solar heaters have almost no monthly fuel cost but require roof or ground space and work best in sunny climates.
• Pool size, your climate, and how many months you want to swim determine which heater type saves you the most money over time.

Gas heaters: fast heat, higher monthly bills

A gas heater burns natural gas or propane to warm pool water and can raise the temperature 6 to 8 degrees in a few hours. This speed makes gas heaters popular for people who want to heat the pool on weekends or for occasional use. If you already have a natural gas line to your home, a natural gas pool heater usually costs less to install than a propane model.

The trade-off is fuel cost. Gas heaters run up your monthly utility bill faster than other types because they burn fuel continuously while the heater is on. In climates where you need heat for many months, or if you want to keep the pool warm all season, a gas heater can become expensive. Gas heaters also need annual maintenance—a technician should inspect the burner and heat exchanger each year to keep them running safely and efficiently.

Heat pumps: efficient in warm climates, slow in cold ones

A heat pump pulls warmth from the outside air and transfers it into the pool water. This is much more efficient than burning fuel because the pump uses electricity to move heat rather than create it. In warm climates where the outdoor air stays above 50 degrees Fahrenheit most of the year, a heat pump can cut your heating costs in half compared to a gas heater.

Heat pumps work poorly in cold weather. When outdoor air drops below 50 degrees, the pump has to work much harder and heats the pool very slowly—sometimes taking days to raise the temperature a few degrees. If you live in a place with cold winters or want to swim during those months, a heat pump alone won't meet your needs. Many pool owners in cooler climates use a heat pump during spring and fall, then switch to a gas heater for winter, or skip heating altogether during the coldest months.

Solar heaters: lowest fuel cost, requires space and sun

A solar heater uses the sun's energy to warm pool water through a system of panels or a mat. Once installed, a solar heater has almost no monthly fuel cost—you pay only for the small amount of electricity the pump uses to circulate water through the panels. Over many years, this can save thousands of dollars compared to gas or heat pump heating.

Solar heaters work best in climates with consistent sunshine and require either roof space or ground space near the pool to mount the panels. They heat the pool slowly—usually 3 to 5 degrees per day on a sunny day—so they work better for maintaining warmth than for rapid heating. On cloudy days or during winter months with short daylight, solar heaters produce little to no heat. Many pool owners combine solar with another heater type: solar does the work on sunny days, and gas or a heat pump takes over when the sun isn't strong enough.

How to choose the right heater for your situation

Start by answering three questions: How many months per year do you want to heat the pool? How much sun does your yard get? What is your budget for installation and monthly operating costs?

If you want to heat the pool for only a few weeks in spring or fall, a gas heater is usually the cheapest option because installation is straightforward and you won't run it long enough for fuel costs to add up. If you live in a warm climate and want to extend your swimming season by a few months, a heat pump pays for itself over time through lower monthly bills. If you have good roof or ground space and your area gets consistent sun, solar can be the most economical choice over the life of the heater, though the upfront cost is higher.

Your pool size also matters. Larger pools take longer to heat and cost more to operate with any heater type. A small above-ground pool might heat adequately with a solar mat, while an in-ground pool usually needs a more powerful heater. Your pool installer can calculate the heater size you need based on your pool volume, climate, and how quickly you want the water to warm.

Installation, permits, and safety considerations

Gas heaters must be installed by a licensed technician and usually require a permit from your local building department. The heater needs proper ventilation to release exhaust gases safely, and the gas line must be inspected before the heater can operate. Installation typically takes one to two days.

Heat pumps and solar heaters have fewer safety restrictions but still benefit from professional installation. A heat pump needs to be positioned where air can flow freely around it, and solar panels must be mounted securely and angled correctly to capture maximum sun. If you're handy, some solar mat systems can be installed as a DIY project, but roof-mounted solar panels should be installed by a professional to ensure they're safe and watertight.

Before you buy any heater, check with your local building department about permit requirements and any restrictions on heater type or placement. Some neighborhoods have rules about where heaters can be located or how they can be vented.

Maintenance and how long heaters last

Gas heaters typically last 8 to 12 years with regular maintenance. Annual inspection and cleaning of the burner and heat exchanger keeps them running efficiently and catches problems early. You should also drain the heater at the end of each season if you live in a freezing climate, because water left inside can crack the heater when it freezes.

Heat pumps last 10 to 15 years and need less frequent maintenance than gas heaters—usually just an annual inspection of the compressor and coils. Solar panels last 20 to 25 years or longer and require almost no maintenance beyond occasional cleaning to remove leaves or dust.

The longer lifespan of solar and heat pump heaters means their higher upfront cost is spread over more years, which can make them cheaper in the long run even though gas heaters cost less to install.

Frequently Asked Questions

Can I use a pool heater with a saltwater pool?

Yes, but saltwater is corrosive to metal parts. Gas heaters designed for saltwater pools have titanium heat exchangers instead of copper, which costs more upfront but lasts longer. Heat pumps and solar heaters work with saltwater pools without special modifications, though you should rinse solar panels occasionally to prevent salt buildup.

How much does it cost to run a pool heater for a month?

This varies widely based on heater type, pool size, and how warm you keep the water. A gas heater might cost 50 to 150 dollars per month during heating season, while a heat pump in a warm climate might cost 20 to 50 dollars per month. Solar heaters have almost no monthly fuel cost. Your pool installer can estimate operating costs based on your local energy prices and climate.

What temperature should I keep my pool at?

Most people find 78 to 82 degrees Fahrenheit comfortable for swimming. Keeping the pool warmer than 82 degrees uses significantly more energy and can promote algae growth. If you're not using the pool, lowering the temperature by a few degrees saves money without making it uncomfortable when you do swim.

Do I need to turn off my heater in winter?

If you live in a freezing climate, yes—you should drain a gas heater before winter to prevent freeze damage. Heat pumps stop working efficiently when outdoor air drops below 50 degrees, so there's no point running one in deep winter. Solar heaters can stay in place year-round but produce little heat during winter months, so many people cover or drain them to prevent damage from ice and snow.

Can I install a pool heater myself?

Solar mat systems can sometimes be installed as a DIY project if you're comfortable with basic plumbing. Gas heaters and roof-mounted solar panels should be installed by a professional because they involve gas lines, electrical work, or structural concerns that require permits and inspection. Improper installation can create safety hazards and void your warranty.