You’ve probably looked at your gas bill after a month of heating the pool and done a slow, pained blink. Maybe a neighbor told you their heat pump costs almost nothing to run, and now you’re wondering whether you’re leaving real money on the table every single month.
Here’s the short answer: a pool heat pump costs roughly $50 to $150 per month to run, while a gas heater typically runs $150 to $400 per month, depending on your pool size, local energy rates, and how often you heat. The gap is real and significant – but the full picture depends on a few variables worth understanding. This article walks through exactly how each heater type burns through money, gives you a worked example with real numbers, and helps you figure out which makes more financial sense for your setup.
How Each Heater Type Uses Energy
Before the numbers mean anything, it helps to understand why the monthly costs differ so dramatically. A gas heater burns natural gas or propane to generate heat directly – it’s essentially a furnace for your pool water. It’s fast (it can raise water temperature by 1°F to 2°F per hour), but it consumes a lot of fuel every time it runs. A 400,000 BTU gas heater is not uncommon for a mid-sized pool, and it burns through roughly 4 therms of natural gas per hour of operation.
A heat pump works completely differently. Instead of generating heat, it moves heat – pulling warmth from the surrounding air and transferring it into the water. This process is much more efficient. For every 1 kilowatt of electricity it consumes, a heat pump delivers 5 to 6 kilowatts of heating energy. That ratio is called the COP (coefficient of performance), and a COP of 5 or 6 is why heat pumps can be so much cheaper to run. The trade-off is that they’re slower – typically raising water temperature by around 1°F to 1.5°F per hour – and they need ambient air temperatures above roughly 50°F to work efficiently. For a deeper look at how climate affects heater performance, Florida Pool Heating’s comparison of heat pumps vs. gas heaters covers this well.
The Real Monthly Cost: A Worked Example
Let’s put this in concrete terms. Say you have a 20,000-gallon pool, you keep it at 82°F, and your heating system runs about 6 hours per day during the swim season.
Gas heater scenario: A 400,000 BTU gas heater at 85% efficiency needs to run roughly 4 to 5 hours to maintain temperature on an average day. At a consumption rate of about 4 therms per hour and a natural gas price of $1.50 per therm (close to the national average), that’s $9 to $11 per day. Over 30 days, you’re looking at $270 to $330 per month. If you’re on propane, multiply that by about 1.3 to 1.4 – so $350 to $460 per month is realistic.
Heat pump scenario: A 100,000 BTU heat pump with a COP of 5.5 consumes about 6.7 kilowatts of electricity per hour. Running 6 hours per day at $0.15 per kWh (near the U.S. average), that’s around $6 per day – roughly $180 per month. In warm-climate states like Florida or Arizona, where the heat pump rarely has to work hard to find ambient warmth, that number can drop to $75 to $120 per month. River Pools and Spas breaks down actual heat pump savings in more detail, including data from real installations.
The monthly difference in that example: roughly $90 to $250 per month in favor of the heat pump. Over a 6-month swim season, that’s $540 to $1,500 in savings.
Side-by-Side Comparison: Heat Pump vs. Gas Heater
| Factor | Heat Pump | Gas Heater |
|---|---|---|
| Typical monthly running cost | $50 – $150 | $150 – $400 |
| Energy source | Electricity | Natural gas or propane |
| Efficiency (COP or %) | COP 5 to 6 (500-600% efficient) | 80 to 95% efficient |
| Heat-up speed | Slow (1 to 1.5°F per hour) | Fast (1 to 2°F per hour) |
| Works below 50°F air temp? | Poorly or not at all (standard models) | Yes, in any weather |
| Upfront cost | $2,000 – $4,500 installed | $1,500 – $3,500 installed |
| Typical lifespan | 10 to 15 years | 8 to 12 years |
| Payback period vs. gas | 2 to 4 years | N/A (baseline) |
Why These Differences Matter for Your Decision
The efficiency gap is enormous on paper, but it only translates to real savings if the heat pump can run in your climate. In the Sun Belt – Florida, Texas, Southern California, Arizona – a heat pump is almost always the smarter financial choice. You’ll get the full benefit of that 5 to 6x efficiency advantage for most of the year. In the Northeast or Pacific Northwest, where nights dip below 50°F even in summer, the heat pump loses efficiency at exactly the times you need it most, and a gas heater may be the only option that reliably keeps up. Willsha Pools covers this climate dependency clearly if you want to map it to specific regions.
Upfront cost cuts the other way: gas heaters are typically $500 to $1,000 cheaper to buy and install than a comparable heat pump. But with monthly savings of $100 or more, the heat pump often pays back that premium in 2 to 4 years. After that, you’re simply pocketing the difference every month. Shasta Pool Supply’s 2025 comparison walks through payback scenarios if you want to run the numbers for your specific setup.
Hidden Costs People Forget to Include
- Pool cover savings: A quality solar or thermal cover can cut heating costs by 50 to 70% on either system. If you don’t already use one, add this before comparing heater types – it changes the math significantly.
- Gas line and electrical upgrades: Installing a gas heater may require running a gas line, which can add $500 to $2,000. A heat pump typically needs a dedicated 240V circuit, which can cost $200 to $600 if one isn’t already nearby.
- Maintenance frequency: Gas heaters have more combustion components and tend to need service more often. Heat pumps are simpler mechanically and often go years without a service call, though the refrigerant system does need occasional attention.
- Propane vs. natural gas: If your home runs on propane, your gas heater costs will run 30 to 40% higher than the natural gas estimates above. This makes heat pumps even more attractive from a monthly cost standpoint in propane-heavy areas.
When Gas Still Makes More Sense
The heat pump wins on running costs in most scenarios, but there are real situations where gas is the better call. If you only heat the pool for occasional weekend use rather than consistently across a long season, gas makes sense because it heats quickly on demand and doesn’t need to run for hours to recover temperature. A heat pump is most efficient when it’s maintaining temperature steadily over time, not playing catch-up from a cold pool. Also, if you live in a region with genuinely cold summers or use an indoor pool where air temperatures are controlled and lower, a gas heater’s weather independence becomes a real advantage.
One more note: if your pool pump has been running rough or making noise, that can mask other efficiency problems. A heater running alongside a struggling pump is never as efficient as the specs suggest – worth a look if your bills seem higher than they should be, or if you’ve noticed anything like the issues covered in this post on pool heater problems after a storm.
A Note on Electricity Rates and Monitoring
Monthly heat pump costs are directly tied to what you pay per kWh. At $0.12 per kWh (below the U.S. average), that 20,000-gallon pool example drops to about $145 per month. At $0.25 per kWh (California or Hawaii levels), it climbs to $300 – which starts to close the gap with gas. Check your utility bill for your actual rate before assuming the heat pump wins in your zip code. AquaDoc pool test kits and water chemistry products won’t affect your energy bill, but keeping your water balanced means your heater isn’t fighting scale buildup on heat exchangers – clogged or scaled heat exchangers force both gas and heat pump systems to run longer to hit target temps, quietly inflating your monthly costs.
Frequently Asked Questions
How much does it cost to run a pool heat pump per month?
A pool heat pump typically costs $50 to $150 per month to run during active heating season. For a 20,000-gallon pool running in a warm climate at $0.15 per kWh, expect closer to $75 to $120 per month. Cooler climates where the heat pump works harder push costs toward the top of that range.
How much does it cost to run a gas pool heater per month?
Gas pool heaters typically run $150 to $400 per month on natural gas during heating season. Propane adds 30 to 40% to those figures, so $200 to $550 per month is realistic in propane-dependent areas. Actual costs depend heavily on how often you heat and your local fuel rate.
Is a heat pump or gas heater cheaper to run for a 20,000-gallon pool?
A heat pump is cheaper to run in almost every scenario for a 20,000-gallon pool, often by $100 to $200 per month. The exception is when ambient air temperatures drop below 50°F consistently, which limits heat pump efficiency and narrows the cost gap with gas.
Do pool heat pumps work in cold weather?
Standard heat pumps lose meaningful efficiency below 50°F and typically stop working well below 45°F. Low-ambient or inverter-style models can operate down to 35°F to 40°F but at reduced efficiency. In regions with cold springs and falls, a gas heater may be worth keeping as a backup or primary option.
What is the payback period for switching from a gas heater to a pool heat pump?
Most pool owners see a payback period of 2 to 4 years when switching from gas to a heat pump, based on monthly savings of $100 or more and an upfront cost premium of $1,000 to $2,500. A long swim season and high local gas or propane prices shorten that window significantly.
The bottom line: in most climates and for pools used regularly throughout a season, a heat pump will cost $100 to $250 less per month than a gas heater – and that difference compounds fast over a 10-year heater lifespan. If you live somewhere cold or heat your pool inconsistently, gas may still be the right tool for the job.