How do heat pump water heaters work?
Heat pump water heaters also use heat pump technology to transfer heat from one place to another. Unlike heat pumps, which are used to heat and cool the air in your home, heat pump water heaters extract heat from the air and move it into a tank to heat water. As a result, heat pump water heaters are often over 3 times more efficient than electric resistance water heaters, and are also more efficient than natural gas water heaters.
Most heat pump water heaters differ from air source heat pumps in that all of the heat pump elements are indoors and combined within a single tank. Most heat pump water heaters are “hybrid” heat pump water heaters and also include conventional electric resistance heating elements to provide backup heating when hot water demand is high.
What are the key benefits of heat pump water heaters?
The primary benefits of using heat pump water heaters are energy savings, reduction of greenhouse gas emissions, and dehumidification.
Energy savings
If you use an electric resistance tank to heat your water, a heat pump water heater will generally cut your water heating bill by more than 50%. You can also usually save on your water heating costs if you replace an oil or propane water heater. There may also be some savings if replacing a gas water heater.
For example, replacing a conventional 50-gallon electric water heater with a 50-gallon HPWH can reduce daily power consumption from around 8 kWh to around 4 kWh. This can save upwards of 1,460 kWh over the course of the year or over $320 — not including the savings from no longer having to run a dehumidifier. During the winter, the cooler dry air from the heat pump water heater is directed to the area around the heat pump or to the outside through ducting.
Reduction of greenhouse gas emissions
Because they operate very efficiently on electricity, heat pump water heaters eliminate fossil fuel emissions from gas, oil or propane water heaters. If replacing a conventional electric water heater, the amount of electricity consumed is reduced, lowering emissions produced in electric power generation. If using electricity that is provided from renewable sources, you further minimize the emissions from electricity generation produced to power your water heater.
Dehumidification
Humidity can be a problem in many basements. A heat pump water heater will dehumidify whatever space it’s in, greatly reducing the need to run a dehumidifier in your basement.
Who can benefit from a heat pump water heater?
Homes with a conventional electric, oil, or propane water heater will see the biggest savings in fuel costs. Homes with a natural gas water heater will generally see some savings. The savings from moving to a heat pump water heater and available rebates will usually offset the added upfront equipment costs and pay back your investment over several years.
Homes with a partially finished or unfinished basement with enough clearance are the best candidates. Heat pump water heaters are slightly taller than most traditional hot water heaters but need sufficient airflow space around the unit to operate. Additionally, they should ideally be placed in an unconditioned space (like a basement that doesn’t have heating) to minimize the use of heat provided by your heating system to heat the water tank. If you have enough space next to your furnace or boiler in an unconditioned space, a heat pump water heater will be able to take advantage of the waste heat generated by your furnace or boiler.
What are the tank sizes for heat pump water heaters?
They are available in a variety of tank sizes, typically 40, 50, 65, and 80 gallons.
Will I need an electric service upgrade?
Most HPWHs run on a 240V circuit; the same as a conventional electric water heater. If you are replacing an electric water heater, there should be no electrical upgrade needed. If you are replacing a gas, oil, or propane water heater, you will need to run a 240V, 30A wire from the breaker box to the water heater. If your circuit breaker box is full, you may need to add a subpanel to make room for the HPWH circuit breaker. If you don’t have enough capacity to add a 30A breaker to your home’s electrical service, you may need to upgrade your service to a higher capacity. If you are unsure, ask your installer about it when they do a site visit. Your installer will assess the current state of your electrical service and make recommendations on what electrical work will be needed for the HPWH. Some newer HPWHs can run from a standard 120V outlet, but they may be less efficient than a 240V unit.
Homeowners switching to heat pumps from inefficient systems that run on fuel oil, propane, or traditional electric resistance can save close to $1,000 per year.