Disclaimer

Estimates, not quotes

The calculators work out figures from the values you enter plus the labelled default assumptions on each page. They are arithmetic, not predictions. Treat every result as a well-explained estimate and check it against your own documents, quotes, labels or measurements before acting on it.

Not professional advice

Heating, cooling and ventilation decisions involve large sums of money, building codes and real safety risks. The calculators and guides are not a substitute for a licensed HVAC contractor, plumber or electrician, for a Manual J load calculation, or for the codes and permits that apply where you live.

Some work must be done by a licensed professional. Refrigerant may only be handled by technicians certified under the US EPA’s Section 608 rules. Gas lines, gas appliances and combustion venting carry fire and carbon monoxide risks and usually need a permit and an inspection. New circuits for air conditioners, heat pumps, electric heaters, tankless water heaters and backup strips must be sized and installed to the electrical code. Nothing on this site tells you that such work is safe for you to do yourself.

Specific limits of this site’s calculators

Equipment sizes are estimates from floor area, climate zone and a few adjustments. They are useful for checking whether a proposed size is in the right range, not for buying equipment. Before you buy, ask for a room-by-room load calculation (ACCA Manual J) and equipment selection (Manual S); for new or altered ducts, a duct design (Manual D). A system that is the wrong size costs comfort and money for its whole life.

Running costs depend on your prices, your equipment’s real efficiency in your climate, how the system is installed and how you use it. Installed costs are national ranges from dated surveys with simple regional adjustments; a written quote for your house is the only real price. Take energy prices from your own bills, efficiency ratings from your equipment’s label or the AHRI directory, and code requirements from your local building department, not from our defaults.

Ventilation, exhaust and humidity figures are code minimums and common rules of thumb. They do not account for specific health conditions, combustion appliances in the house, or radon, mould or other hazards that need a specialist.

Sources and updates

Default figures come from public sources named on each calculator’s assumption table and on the methodology page, with the date they were last checked. We update them when sources change and at least once a year, but a default may be out of date on the day you use it. Your own figures are always better than ours.

Advertising

Advertisements on the site are served by Google AdSense and are labelled as advertisements. We do not choose or endorse the products advertised, and an advertisement’s appearance next to a calculator does not mean the calculator was built with that product in mind.

Errors

If a calculator or a guide is wrong, we want to know. Write to contact@hvacscalculator.com or use the contact form; error reports are checked first. Our editorial policy explains how corrections are made and recorded.