The CO2 heat pump boiler system that will revolutionize home heating.


I started 2040 Energy last year with a simple vision: to heat every home in America with clean electric heat.

Today I’m writing to introduce the vision for the product line that will help make this a reality: RenewaBoiler.

The Problem

Nearly every building in America is heated by burning fossil fuels. The climate impact of these fuels is massive: about 700 million tons of greenhouse emissions per year, or 10% of the nationwide total. We desperately need an alternative heat source.

The mode widely-accepted clean energy solution for building heat is the air-source heat pump. Unfortunately, today’s air-source heat pumps have two big problems:

  1. Their performance struggles in cold weather.
  2. Their output temperatures are not very hot.

The cold-weather problem means that in much of the country, heat pumps generally require a backup furnace. The output temperature problem means that forced-air heat pumps often feel uncomfortably cool, and radiant heating systems typically can’t use a heat pump at all.

RenewaBoiler is designed to solve both of these problems.

The Solution, Part 1: CO2 Refrigerant

Because it uses carbon dioxide as its refrigerant, RenewaBoiler can achieve much high temperature output than any existing heat pump.

Traditional refrigerants exchange their heat by condensing into a liquid. This condensation happens at a constant temperature, which sets an upper limit on how hot it can heat the air or water. For most heat pumps, this limit is around 120°.

CO2 refrigerant is different because it never condenses. Instead, it will transfer heat to the air or water across an increasing temperature range of up to 300°F.

This means there is no limit to our output temperature! We can make a much more comfortable forced-air system with slower, warmer airflow. And we can easily run radiant heating systems that require very hot water.

Side Benefit: a Climate-Friendly Refrigerant

There’s another important benefit to using CO2. When traditional refrigerants inevitably leak into the atmosphere, they are extremely high contributors to global warming – 2,000 times more potent than CO2. Because of this problem, some governments are even beginning to require alternative refrigerants.

CO2 refrigerant is one of these climate-friendly alternatives, as it has a negligible climate impact at the scale involved for a heat pump.

The Solution, Part 2: The Cascade System

By combining two heat pumps in a “cascade” configuration, RenewaBoiler can operate at much lower outdoor temperatures than heat pump available today.

It’s a common misconception that heat pumps cannot operate in the extreme cold. They can! Commercial deep freezers chill to -40° and below. RenewaBoiler applies this same technology in an air-source heat pump to operate effectively when it’s deep-freezer cold outside.

The limiting factor is how much temperature “lift” can be accomplished with a single heat pump. To get all the way from -40° outside air to 160° hot water, we need to split the work across two heat pumps.

This is how RenewaBoiler works: an air-source heat pump outdoors, a water-source heat pump indoors, and cool water flowing through a pipe connecting them. The outdoor unit extracts heat from frigid winter air and adds it to the water to maintain a temperature of around 40-60°. The indoor unit extracts that heat from the water and adds it to your heating system.

The result is much better performance in subzero temperatures than any other heat pump.

Side Benefit: Geothermal Compatibility

Another benefit of the cascade system is that the indoor unit is completely compatible with a ground-source (geothermal) system. In fact, you can think of the outdoor unit as simulating a ground loop in the wintertime.

Ground-source is a niche player in the heating market, but it’s an important and growing niche. RenewaBoiler is a perfect match for it.

Side Benefit: Easier Installation

Yet another benefit of the cascade system is a much easier installation process. A traditional heat pump requires high-pressure refrigerant piping to be run from outdoors to indoors and back again. Installing this in a customer’s home is difficult and requires special training and equipment.

Running a cool low-pressure water line between two factory-sealed heat pumps is much, much easier. With push-to-connect fittings and flexible PEX tubing, it can even be done by many homeowners. This simpler installation process will greatly lower the overall system cost.

Why Radiant Heating

Radiant heating is a much smaller market than forced-air. However, it makes a great starting point for RenewaBoiler because:

  • The radiant heating market isn’t served by any cleantech product today.
  • Radiant systems tend to be more expensive to service and maintain, and tend to be in larger and historic homes. These customers are more able and willing to pay a premium price for their heating system. (Until RenewaBoiler achieves some manufacturing scale, it is going to be a bit pricy.)
  • Cooling functionality is not required.
  • In my experience local to the Twin Cities area, a large proportion of climate-motivated consumers have this type of heating system. It’s a natural correlation of our politics and geography.

Forced-air heating is critical to the long-term success of RenewaBoiler. But it’s going to take lower prices and more functionality to be competitive than we can accomplish in the near term.


If you think RenewaBoiler sounds like an interesting product, I’d love to hear from you! The three best ways to get involved are:

  • Email me directly at [email protected]. I read and respond to every email!
  • Subscribe to my email list below to stay informed about RenewaBoiler
  • Add a comment or question below.