The thermal balance point is the point at which a heat pump can move heat into the home at the same rate the home loses its heat. Above this point, the heat pump will not need any additional help to heat the home. But below it, the heat pump will need auxiliary heat with it to help maintain the temperature.

The thermal balance point is not a set number and depends greatly on the heat loss of the individual home (Manual J) and the specific capacity of the unit chosen (Manual S). This point can be as high as the 60s (unfortunately) or as impressively low as the negative numbers. 

On the other hand, the economic balance point is specific to dual-fuel heat. It's the point where it's more cost-effective (economical) to switch over to the secondary heat, such as natural gas, propane, or oil.

The actual number depends on the Manual J of the home and Manual S of the equipment, as well as the costs of electricity and secondary fuel. It is not a set number, and it can even change from one year to the next. For example, a customer may not have access to natural gas, so they are dependent on propane delivery or fuel oil delivery, which could possibly have a much higher cost than natural gas. That means two identical homes in a similar area could have different economic balance points because of the differences in secondary fuel costs.

All-electric homes don’t have an economic balance point. Even though the heat pump loses capacity as the outdoor temperature drops, and even though it needs assistance from the electric heat, it will still move more heat from the outside to the inside with less kilowatt energy than the same kilowatt energy for electric heat (as long as it's working properly). Even if the heat pump is running nonstop, it's moving more heat inside for less energy than if it were to run electric heat elements alone.

This tech tip isn’t meant to convince you to use heat pumps but inspire you to learn more about them so we can solve more problems together. I work on electric heat pumps and furnaces of all kinds: 60% furnaces, 80% furnaces, 90%+ furnaces, using natural gas, propane, and oil. It's all technology, each with its benefits and drawbacks.

—Ty Branaman