Heat pumps: How much heat does your home really need?

Heat loss calculations help determine the size of heat pump a home needs, and getting the estimate wrong can leave a system inefficient or uncomfortable. As more homeowners seek to check installers’ recommendations themselves, experts say the calculations can vary widely and may overstate a property’s heating needs.

The article describes US tools such as Cool Calc and AutoHVAC, and the UK web app Heatpunk, which let users enter details about their homes. A Purdue University study of calculations for about 75 US households found that estimates often overstated heat loads by a factor of two or more; some homeowners paid over $1,000 for a survey, with one charge reaching $2,500. Oversized systems can use more energy and switch on and off frequently, causing uncomfortable temperature swings.