Last week we talked about using air source heat pumps to efficiently heat and cool South Portland homes. In addition to air source heat pumps, which heat and cool your living space, there are also hot water heat pump systems, which can provide your home with reliable, affordable hot water.

This week, we are focusing on heat pump water heaters: how they work, why they’re beneficial, and your options when getting one.

What are heat pump water heaters?

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Heat pump water heaters use ultra-efficient technology to pull heat from a room and into a water tank to heat it, similar to how air conditioners work. Because these systems are moving heat from one place to another as opposed to creating heat directly, they are roughly two to three times more energy efficient than traditional electric water heaters. In addition, they have the capacity to store a lot of hot water, making them extremely reliable systems.

Heat pump water heaters are at times referred to as hybrid electric water heaters due to their ability to switch to electric resistance heating elements for times when demand exceeds what the heat pump can produce. This means Maine households can be sure they will have plenty of hot water and energy savings all year round.

Benefits of heat pump water heaters


According to Efficiency Maine, tens of thousands of Mainers own heat pump water heaters. They are popular due to their many benefits: producing plentiful hot water, saving households’ money on energy costs, and dehumidifying your basement — where the heat pump water heater is — while simultaneously heating water.

Considering around one fifth of a household’s energy use goes toward heating water, the installation of a heat pump water heater offers significant cost savings for a household. Typically, one unit of electricity used will result in three units of heat added to the water in a heat pump water heater’s tank. Due to this high efficiency, Energy Star estimates that the installation of a heat pump water heater can save the average Maine household over $300 annually, and more than $3,500 over the course of the system’s lifetime.

In addition, many of these systems have a 10-plus year warranty, ensuring lower costs and reliable hot water for the lifespan of the system. Plus, with current incentives, these systems can be less expensive than traditional electric water heaters.

An additional benefit to installing a heat pump water heater in your home is that these systems dehumidify while they heat water. In fact, they can remove roughly a gallon of water from the air daily.

Getting a heat pump water heater (with help from Efficiency Maine)

Efficiency Maine acts as a hub for heat pump water heater information. The website has detailed information about installers and retailers, and breaks down the logistics and benefits of these systems.


Efficiency Maine offers numerous rebates and financing for efficient electric systems including heat pump water heaters. They currently offer a $750 mail-in rebate on heat pump water heaters. With this, it is estimated that the energy savings of your system could cover the installation cost in just two years. In addition, Efficiency Maine has a no-cost heater for low income qualifying households and multiple instant discount offers at varying stores.

For more information about heat pump water heaters, rebate opportunities and retailers and installers in our city, visit

Our Sustainable City is a recurring column in the Sentry intended to provide residents with news and information about sustainability initiatives in South Portland. Follow the Sustainability Office on Instagram and Facebook @soposustainability.

Mia Ambroiggio is a Greater Portland Council of Governments Resilience Corps Fellow serving in the Sustainability Office. She can be reached at

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