How much heat could a heat pump heat if a heat pump could pump heat? Technically, the answer is about 3.
“Heat pump.” What a dumb, geeky name for what is arguably the most important climate modification device known to man. Heat pumps are really just refrigerators operating in reverse. Spelling-wise that would be a rotaregirfer. OK, “heat pump” is comparatively a better name.
Almost every building in the U.S. has one or more heat pumps — usually in the form of air conditioners or refrigerators. Air conditioning has been tremendously important to society. Could you imagine working in a high rise in Miami, Dallas, Phoenix or Atlanta on a hot summer day without air conditioning? Now this established technology for cooling is now being deployed throughout the world for clean and efficient heating.
So why is there so much excitement about heat pumps? Because they generate three times more heat than the electrical energy it takes to run the heat pump. Essentially, they are three times more efficient than an electric heating system or electric hot water heater — and almost always cheaper to operate than a gas furnace or gas hot water heater when the power source is from solar.
Most air-to-air heat pumps have an efficiency (actually a coefficient of performance) of 300%. Heat pumps achieve this high efficiency — without getting arrested for breaking the first law of thermodynamics — by moving heat from outdoors on a cool or cold day, to indoors to heat a building or water. Heat is removed from the outdoor air (making the outdoor air even colder), and then transferred to the indoor air (or water).
For example, a 2200 sf home in San Jose uses 520 therms of methane (AKA natural gas) for heating. At current PG&E rates heating the home would cost about $1,100. Converting to a heat pump would reduce annual heating costs (under the electric heating rate) to about $1,000. If the home had rooftop solar, heating the home would drop to about $300 per year! Many cities have rebates of up to $4,000 for the installation of a heat pump HVAC system.
The hottest type of heat pumps now, figuratively speaking, are heat pump water heaters (HPWH). These HPWH systems are a direct replacement for traditional methane or electric tank water heaters. For example, a 65 gallon methane hot water heater would use about 120 therms or $264 per year. Converting to a HPWH, energy consumption would drop to about 870 kwh or $250 per year. If the home had rooftop solar, heating water would drop to about $70 per year. Many cities have rebates of up to $2,000 for the installation of a heat pump water heater.
It is very likely that you will be electrifying your home in the future. EVs, heat pump water heaters and HVAC systems and induction cooktops are better, cleaner, safer and often cheaper than their polluting fossil fuel ancestors. For more practical information about heat pumps, please tune in to this week’s Energy Show.