This calculator is built for comparison, not a universal forecast. It keeps the assumptions on screen so a homeowner can replace generic inputs with an actual utility rate and the exact heater specification.
This calculator is built for comparison, not a universal forecast. It keeps the assumptions on screen so a homeowner can replace generic inputs with an actual utility rate and the exact heater specification.
Enter the temperature event, not a monthly guess
Begin with one defined event: for example, move 14,000 gallons from 75°F to 82°F. That is a 7°F rise and a water-only requirement of 817,320 BTU. Monthly totals become easier after one event is credible: multiply by expected events or model ongoing daily heat loss separately.
Use efficiency correctly
Gas thermal efficiency is entered as a decimal, so 84% becomes 0.84. COP belongs to heat pumps and represents heat delivered relative to electrical energy consumed at specified conditions. A COP of 5 means roughly five units of heat delivered per unit of electrical energy at that rating point; it does not mean the unit will hold COP 5 in every season. Electric resistance is modeled near one unit of heat per unit of electrical energy at the element, while distribution and system effects remain outside the water-only baseline.
Choose a loss factor carefully
The loss-factor control is a scenario tool, not a measured universal correction. Set it to zero to compare pure water heating. Then test higher scenarios to see how exposed operation changes the economics. A better long-term approach is to calibrate the factor against actual run time, weather and energy use.
Include circulation
A heater usually depends on the pool pump. If heating requires extra pump hours beyond normal filtration, add pump kilowatts × extra hours × electricity price. Do not charge all ordinary filtration time to the heater if that runtime would have occurred anyway.
Read the output as a range
The least-expensive calculated column is not automatically the best choice. A slower system may miss the desired start time. A faster system may trigger utility upgrades. Solar may have low operational cost but high site dependence. Use the result to ask better questions when collecting installed quotes.
Privacy-friendly design
No address or account login is needed. The calculator can run in the browser and forget the inputs on refresh. Local rates can be entered from a bill, including supply and delivery charges that apply to incremental use.
The goal is clarity: a user should be able to explain why the result changed. If COP falls, heat-pump cost rises. If gas efficiency rises, therms fall. If the pool is covered and losses fall, every heating method benefits.
Frequently asked questions
What electricity rate should I enter?
Use the marginal all-in rate that applies to added consumption, including relevant supply and delivery charges. If pricing varies by time, calculate separate cases.
What COP should I use?
Use the model's published COP at air, water and humidity conditions close to your expected operation. Run a lower-COP scenario for cool weather.
Does the calculator include installation cost?
No. It estimates operating energy. Compare installation, utility upgrades, maintenance and expected service life separately.