Pool heating is often the single largest operating expense for pool owners who use it. Understanding the real monthly cost of each heater type — gas, heat pump, and solar — before making a purchase or recommendation prevents expensive surprises. The math is straightforward once you know the variables.
| Type | Upfront Cost | Monthly Running Cost | Response Time | Best For |
|---|---|---|---|---|
| Gas (natural gas) | $1,500–$3,000 | $180–$350 | Fast (2–4 hrs) | On-demand heating, cold climates |
| Gas (propane) | $1,500–$3,000 | $350–$700 | Fast (2–4 hrs) | No natural gas access |
| Heat pump | $2,500–$4,500 | $50–$120 | Slow (12–24 hrs) | Mild climates, daily heating |
| Solar panels | $3,000–$6,000 | Near zero | Very slow (days) | Season extension, warm climates |
| Solar cover only | $50–$200 | Near zero | Passive | Heat retention, any climate |
Natural gas pool heaters are rated in BTU/hour output. The most common residential sizes are 250,000, 300,000, and 400,000 BTU/hr. A 400,000 BTU heater running at full output consumes approximately 4 therms of natural gas per hour.
At a national average natural gas price of $1.20 per therm:
In practice, pool heaters don't run at full output continuously. A thermostat-controlled heater cycles on and off to maintain the set temperature. In mild shoulder-season weather (pool at 72°F, target 82°F, ambient 65°F), a 20,000-gallon pool might run the heater 3–4 hours/day to maintain temperature — costing $175–$250/month.
In cold weather or when heating from 60°F to 84°F, runtime increases substantially. Propane costs 2–3x more per BTU than natural gas in most markets, making propane pool heating expensive in cold climates.
Heat pumps are rated by COP (coefficient of performance) — the ratio of heat output to electricity input. A quality heat pump (Hayward HeatPro, Pentair UltraTemp) achieves COP 5.0–6.5 in warm air temperatures (above 60°F). As air temperature drops, COP drops. Below 50°F ambient, most pool heat pumps stop functioning efficiently.
At COP 5.0 and $0.15/kWh electricity:
Heat pump efficiency drops in cold weather. In climates where night temperatures regularly fall below 55°F during swim season, heat pump effectiveness is limited. In Florida, Texas, Arizona, and Southern California, heat pumps are the dominant and most cost-effective choice.
Solar pool heating uses the existing pool pump to circulate water through roof-mounted collector panels. The operating cost is essentially the incremental electricity cost of running the pump at the flow rate required by the solar system — typically included in the existing pump schedule at minimal additional cost.
Solar works best for extending the swim season by 2–4 months rather than providing on-demand heat. They can raise pool temperature by 8–15°F above ambient on sunny days. In the Southwest, well-designed solar systems can maintain comfortable swimming temperatures from April through October without any gas or electric heating.
The $3,000–$6,000 installation cost ($1,500–$3,000 for equipment, $1,500–$2,500 for installation) has a payback period of 2–7 years depending on local energy costs and climate.
Regardless of heater type, a pool cover dramatically reduces heating cost. A solar cover (blue bubble-wrap style) reduces evaporative heat loss by 50–70%. Covering the pool overnight when not in use can cut gas heater monthly costs by $75–$150 and significantly extend heat pump efficiency.
A quality solar cover costs $50–$150 for the blanket plus $100–$250 for a reel system to make it easy to deploy and remove. The ROI on a pool cover is typically measured in weeks, not months, for any heated pool.
When servicing heated pool accounts, note the heater type and age in SplashLens. Gas heaters over 10 years old often have reduced efficiency (heat exchangers scale up, burner assemblies wear). A heat efficiency check — comparing thermocouple response times and burner firing duration to temperature rise — can identify aging heaters before they fail mid-season.
Log heater model, installation date, last service, and any error codes for every heated pool account in SplashLens. Free for pool service professionals — offline-first, no account required.
Open SplashLens Free →A 400,000 BTU gas pool heater running 6 hours per day costs approximately $180–$350 per month at current natural gas rates ($1.00–$1.50 per therm). Propane costs 2–3x more than natural gas for the same heat output. Running a gas heater only to raise temperature and then using a pool cover to maintain it reduces monthly cost significantly.
Yes, significantly. A heat pump with a COP of 5.0 uses 1 kWh of electricity to produce 5 kWh of heat. At $0.15/kWh electricity, a heat pump costs $50–$120/month to maintain pool temperature — vs $180–$350/month for gas. Heat pumps cost more upfront ($2,500–$4,500) but pay back in 2–4 years of operation.
A general rule: 1 BTU per gallon per degree of temperature rise needed. A 20,000-gallon pool needing to rise 15°F requires 300,000 BTU of heating capacity. Account for heat loss to air temperature, wind, and pool cover use. Most residential pools use 250,000–400,000 BTU gas heaters or 100,000–140,000 BTU/hr heat pumps.
Solar pool heaters circulate pool water through roof-mounted collectors that absorb solar heat. Operating cost is essentially zero beyond pump electricity (already paid for the pool pump). Solar panels add $3,000–$6,000 installed but operate for 10–20 years with minimal maintenance. They can extend the swim season by 2–4 months in most US climates.
Yes — significantly. A solar cover (bubble wrap-style) reduces heat loss by 50–70% overnight and captures additional solar energy during the day. Using a pool cover consistently reduces gas heater monthly costs by $60–$150 and extends heat pump efficiency. A cover is the single highest-ROI investment for pool heating in most climates.