Making an energy-efficient, fully-electric heating system for the Upper Midwest required a new way of thinking about heating and cooling.


For homeowners in the Twin Cities and throughout the Upper Midwest, running a furnace, hot water heater, and air conditioner is a major expense. And for many families, these appliances are the largest source of climate-changing greenhouse emissions.

The 2040 Energy home comfort system dramatically lowers the carbon footprint of heating, cooling, and hot water – with costs comparable to natural gas heating (and far cheaper than propane).

To accomplish this feat, we had to design a new way to heat and cool. Unlike a traditional furnace and air conditioner that heat and cool the air directly, the 2040 system heats and cools water, then flows this water through a heat exchanger in your ductwork to heat or cool your home.

Using water like this has some major advantages:

  • Energy storage means lower costs – The heating energy can be stored in a water tank, so the system can run hardest when it is most cost-efficient: when electricity is cheaper and when the outside temperature is milder.

  • More precise, comfortable air temperature – The amount of heating or cooling can be set very precisely by controlling how fast the water flows through the air handler. This means your system can blow a gentle stream of comfortable air all day long, rather than periodically sending out blasts of uncomfortably hot or cold air.

  • Compatibility with boilers and radiators – Many homes already use water for heating, via a boiler system with cast iron radiators. While the 2040 system is currently meant to replace forced air furnaces only, boiler replacement is definitely on our future roadmap.

Now let’s take a closer look at how the system actually works, by taking a tour through each of the components.


A hydronic air handler blows the heating and cooling through your home.

An air handler is essentially a furnace without the gas-burning parts. In our system, a hydronic air handler flows the hot or cold water through coils of copper tube in the air handler, and blows a fan through the coils to transfer the heat or cooling into your home’s air through the ductwork.

The air handler runs continuously to keep your home at an even temperature, regardless of the weather outside. The heat transfer is controlled very precisely by the speed and temperature of the water flowing through the coils, so your home is always exactly the temperature you want it.

An air-to-water heat pump outdoors provides cooling and light heating.

The workhorse of the 2040 system is an air-source heat pump located outdoors that heats and chills water. This machine expels heat from the house during the summer, and extracts heat from the outdoors during the winter. It is 3-4 times more efficient at heating than old-fashioned baseboard heat, and more efficient at cooling than any standard air conditioner.

The hot or cold water from this system can go directly to the air handler, be stored in a tank for later use, or be fed into the second stage of heating when more power is needed.

An indoor heat pump provides powerful heating and hot water.

As the weather gets colder, air-source heat pumps become less powerful and efficient. To meet the home’s heating needs at very cold temperatures, the 2040 system includes a second heat pump indoors for an extra boost of power. This dual-stage design also allows the system to efficiently maintain a high temperature (up to 140° F) for the hot water heater.

During cooling season, the indoor heat pump adds another benefit: it can simultaneously chill water for air conditioning while heating the hot water heater. This process is extremely energy-efficient, and means your hot water in the summer is essentially free.

An electric boiler provides reliable backup for extra-cold days.

At extremely cold temperatures (below -5°F), the dual heat pump system becomes ineffective. So as a backup, the system includes an electric resistance-heat boiler. This unit also provides redundancy in case of mechanical problems with either of the heat pumps.

A water tank stores thermal energy for heating.

The 2040 system includes a 150-gallon storage tank, capable of storing several hours of heating energy. Thermal energy storage allows the system to run the heat pumps harder when they are more efficient, when the outdoor temperature is milder. It also allows homeowners to take advantage of lower electricity prices by using the energy during “off-peak” periods when there is low demand and high supply. (And we are pursuing partnerships with utilities to achieve even greater savings with our unique technology.)

An indirect water heater uses the efficient heat pumps for hot water.

A 60-gallon water heater with a heat exchanger leverages the efficiency of the system to heat water. Heated water from the indoor heat pump is run through a coil inside the bottom of the water heater (where cold water enters). The coil preheats this water up to 120°, supplying most of the energy required to heat the water. An electric heating element at the top of the tank (where hot water exits) adds supplemental heat as necessary.

The water from the heating system is always kept separate from the potable water in the water heater.


If you have more questions about the system, please let me know! Feel free to write a comment below, or email me directly at [email protected].

Thanks for reading!


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