Compare pool heat pump and gas heater costs using your energy rates, equipment quotes, maintenance, and planned ownership period.
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Table of contents
How to use our Pool Heat Pump vs Gas Heater Lifetime Cost Calculator
- Enter Annual pool heat needed from an energy audit, prior heater-use estimate, or contractor load estimate. This is heat delivered to the water, not fuel purchased.
- Choose Gas heater fuel, then enter your bill's usage-based Electricity rate and matching gas or propane rate.
- Enter the Comparison period, both installed quotes, and yearly maintenance estimates.
- Open Advanced options and replace the example Heat pump efficiency, Gas heater efficiency, and service-life values with model or contractor information when available.
- Click Calculate, then check whether the yearly running costs and fuel use look reasonable against prior bills before using the lifetime savings and break-even year for a purchase decision.
Definitions
Annual pool heat needed: Useful heat delivered to pool water in one year, measured in million Btu per year. It is not the amount of electricity, natural gas, or propane purchased.
COP: Coefficient of performance. A heat pump COP of 5 means it delivers about 5 units of heat for each unit of electricity used under its rated conditions. [1]
Gas heater efficiency: The percent of fuel heat delivered to the pool. An 84% efficiency means 84% of the fuel's heat is counted as useful pool heat.
Therm: A natural-gas billing unit equal to 100,000 Btu. [1]
Lifetime ownership cost: Installed units, yearly energy, and yearly maintenance over the Comparison period.
Break-even year: The first completed year when cumulative heat-pump cost is no greater than cumulative gas-heater cost.
Common mistakes and quick fixes
Mistake: Entering purchased fuel or electricity in Annual pool heat needed.
Fix: Enter useful heat delivered to the pool in million Btu per year; the calculator estimates purchased electricity or fuel separately.
Mistake: Using a natural-gas price after choosing propane in Gas heater fuel.
Fix: Choose the actual fuel first, then enter the matching Natural gas rate or Propane rate from a bill or supplier quote.
Mistake: Treating Heat pump efficiency as a percent.
Fix: Enter the heat pump COP from its performance information, such as 5, rather than 5%.
Mistake: Entering a COP as Gas heater efficiency.
Fix: Enter the gas heater's thermal efficiency as a percent, such as 84, and keep it no higher than 100.
Mistake: Comparing only Heat pump yearly running cost and Gas heater yearly running cost.
Fix: Use Heat pump savings over the comparison period because it also includes installed costs, maintenance, and replacement units.
Mistake: Counting a replacement due exactly at the end of the Comparison period.
Fix: Do not add that unit because it is not used within the selected period; the calculator excludes it.
Limitations & Key Assumptions / Boundary Conditions
- Results use your entered annual pool heat estimate. They do not calculate heat demand from pool size, cover use, water temperature, weather, or location.
- Heat-pump COP can change with outdoor temperature, humidity, water temperature, and operating conditions. A single COP is a planning input, not a guaranteed yearly performance value.
- Costs are held constant in today's dollars. The calculation excludes utility price changes, inflation, financing, discounting, tax credits, rebates, salvage value, and unexpected repairs.
- Each replacement uses the entered installed cost and occurs at the entered service-life interval. Actual equipment life and replacement quotes can differ.
- Existing utility customer charges are excluded because they commonly continue even without pool-heater use. Include only usage-based energy rates.
- Break-even is checked at completed end-of-year points, so it is not an exact calendar date. A heat pump can catch up and later become more expensive after a replacement; the lifetime total remains the main comparison.
Methodology
Energy use and yearly cost
The calculator gives both heaters the same Annual pool heat needed. Heat-pump electricity use is based on COP and 3,412.141633 Btu per kWh. Natural gas uses 10 therms per million Btu before efficiency losses. Propane uses 91,452 Btu per gallon before efficiency losses. [1]
heat pump kWh per year = annual pool heat needed x 1,000,000 / (heat pump COP x 3,412.141633)
natural gas therms per year = annual pool heat needed x 10 / (gas heater efficiency / 100)
propane gallons per year = annual pool heat needed x 1,000,000 / (91,452 x gas heater efficiency / 100)
yearly running cost = yearly energy use x matching energy rate + yearly maintenance
Lifetime cost and replacement timing
The calculator counts the initial heater plus replacements that occur before the end of the Comparison period. A unit due exactly at the endpoint is excluded. Installed cost is multiplied by the number of units purchased, then yearly running cost is multiplied by the comparison years.
units purchased = ceiling(comparison years / service life)
lifetime ownership cost = installed cost x units purchased + yearly running cost x comparison years
heat pump savings = gas heater lifetime ownership cost - heat pump lifetime ownership cost
Break-even and example
The calculator checks year 0 and each completed year through the selected period. It returns the first year when cumulative heat-pump cost is no greater than cumulative gas-heater cost.
first-year ownership cost = installed cost + yearly running cost
For example, if a heat pump costs $6,000 installed and $657 per year to run, its first-year ownership cost is $6,657. If a gas heater costs $4,000 installed and $1,061 per year to run, its first-year ownership cost is $5,061. The heat pump starts higher, but its lower yearly cost can close that gap over time.