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Domestic Water Heaters

Domestic Water Heaters accounts for about 18% of your home's energy use according to energy.gov.  This is an excellent website to find out more about your choices. There are three main alternatives to traditional electric or oil burner water heaters, Solar Thermal, Tankless, and Heat Pump. 


Solar Thermal Water Heating

Solar thermal water heating (using heat from the sun to warm water) is the most cost- and energy-efficient renewable energy alternative for water heating. This is because renewable electric systems, like solar electric and onsite wind power, have substantial energy loss when converting electricity to heat. With solar thermal water heating, there are a multitude of options, and the best choice for you will depend on your local climate and architectural factors, visit energy.gov for more information


  • You must have space on your roof that gets fairly direct sunlight and it must face in a southerly direction. 

  • You may want a second storage tank which holds the water as it preheats (there is a MA rebate for this) which would require additional space near your existing water heater.

  • You will need an alternate source of heat during the winter months. This can be an electric element in the tank itself or a fossil fuel system. 

  • You can choose a drain-back system to eliminate the possibility of freezing or overheating. 

  • Maintenance: The propylene-glycol in the solar piping should be replaced every 5 years approximately because it breaks down over time. Some systems have only water in the pipes. Some systems have an expansion tank just as a conventional water heater does. These need replacing every 5-10 years. 

  • Longevity: SHW systems are installed with a stainless steel tank. The system should last 20 years or more but does depend on water quality.

  • Cost: These systems run about $9000 but there are significant incentives in MA that bring the cost down.

  • There is a 26% federal tax credit (2020 that drops to 22% in 2021) on solar hot water heaters.


Tankless Water Heater

Tankless water heaters, also known as demand-type or instantaneous water heaters, provide hot water only as it is needed. They don't produce the standby energy losses associated with storage water heaters, which can save you money.


  • Tankless water heaters are especially good when you spend large amounts of time away, such as in a second home, because they are not wasting energy to keep a tank of water warm when not in use.

  • Tankless water heaters work best for smaller demands. This may not be the best choice for a family which draws large amounts of hot water all day long.

  • Gas fueled Tankless water heaters must vent through an outside wall.

  • Tankless water heaters are much smaller and can fit in more awkward spaces than a full sized water tank.

  • Gas fueled tankless water heaters need gas piped to their location. 

  • They do not need to be situated next to a furnace/boiler. 


​Heat Pump Water Heater

Heat Pump water heaters transfer heat from the surrounding air outside the tank to the water inside the tank  like a refrigerator but running in the opposite direction. These can save you money, reduce your carbon footprint, and help you electrify your home. There are some things to consider to be sure they are the right fit for your house and lifestyle.


  • Heat Pump water heaters can help dehumidify an area.

  • Heat Pump water heaters pull heat from the surrounding air, so they work best in a warm area like a furnace room to use the residual heat. If installed in a living space it will draw the heat from your conditioned air.

  • It must be installed in a large enough space so that there is adequate circulation, ~1000 sqft.

  • It should be installed away from bedrooms because the fan makes noise between a refrigerator and portable dehumidifier. 

  • Air source heat pump water heaters have a fan and condenser on top so they require more headroom than an ordinary hot water tank.

  • There is a Massachusetts incentive of $600 for a 55 gallon tank or smaller.

  • Air source heat pump water heaters have an electric resistance back up for winter and when the draw on it is high.

  • Be sure the unit meets the Northern Climate Efficiency Specifications which tests reflect colder ambient air and water intake.


For more information see Energystar.gov