Terms of use

What you are using

This site publishes planning arithmetic about swimming pool heating. Results are estimates derived from your inputs, published data and stated assumptions. They are not a quote, not an engineering design, not a code compliance review, and not a guarantee that your pool will reach or hold any temperature at any cost.

Professional advice and local rules

Installing or replacing a pool heater involves gas piping, combustion venting, electrical service, equipotential bonding and permits, all of which are governed by local code and none of which this site evaluates. A licensed contractor's assessment and your jurisdiction's requirements control. Where they conflict with anything here, they win.

Accuracy

Sourced figures carry the date they were retrieved and go stale. Assumptions are labelled and may not fit your case. The model runs on climate averages and does not attempt to predict weather. Use of the results is at your own discretion and risk.

External links

Links to publishers are provided so a figure can be verified at its source. This site does not control those sites and is not responsible for their content.

Specific limits on the estimates

The model runs on twenty-year monthly climate averages. It cannot tell you what a particular week will do, and a season's actual cost will differ from the estimate by whatever margin your weather differed from the average. Sizing figures carry a design margin for exactly this reason, and that margin is a judgement rather than a standard.

Several inputs are stated assumptions rather than measurements — how much wind reaches your water, how much sunlight your pool retains, how a cover performs. Each is listed on the methodology page, which also names the page where it can be changed, directly or by picking a different option. A page that uses an assumption does not always offer a control for it, and one, a fixed 12-hour daylight window used to split cover hours, cannot be changed anywhere. If you leave them at their defaults, the output carries their uncertainty.

Energy prices are published averages at the retrieval date shown. Your marginal rate, on your rate plan, in your billing period, is the number that will actually appear on your bill, and it is frequently higher.

Safety

Nothing here is safety guidance. Thermal pool covers are not safety covers and will not support a person or an animal. Water temperature affects people differently and elevated water temperatures carry real medical risk for some, particularly in spas; that is a question for a physician, not for a calculator.

Use of the site

You may read, print and cite these pages, including for commercial purposes, provided the source is named. Do not present the calculators or the text as your own work, and do not represent output from this site as a professional opinion, an engineering calculation, or a compliance determination.

Availability and changes

The site is provided as-is, with no undertaking that it will remain available, that figures will be updated on any schedule, or that a page you relied on will still exist. Terms and figures both change; the date at the foot of each page is when that page's content last changed.

Liability

To the fullest extent permitted by law, no liability is accepted for any decision taken on the basis of these estimates, including equipment purchases, installation work, or energy costs incurred. The estimates are a planning aid and the decision remains yours.