Most homes in our area use natural gas for heating. When natural gas is burned in your furnace, it can be pretty efficient — up to about 95% efficient if you have an advanced system. But even the best natural gas heaters have some losses, for example, some of that heat goes out the flue as wasted energy. But no matter how efficient they are, natural gas furnaces consume fossil fuel and convert it to carbon dioxide. There’s just no way around that.

So, let’s compare natural gas–powered heating with electric heating. Most older electric heaters are called “electric resistance heaters” because when electricity flows through wires, they glow and get hot due to their resistance … just like what’s going on inside your toaster. They also create heat that is essentially 100% efficient: all the electrical energy is transformed to energy in the form of heat — well, where else would it go?

But electricity can be a pretty inefficient energy source on its own — only about a third of the energy generated from a natural gas powerplant makes it to your home due to transmission losses. So you’re not really getting all of that “100% efficiency”. In fact, electric resistance heaters are so inefficient, it’s illegal to use them in central heating systems.

So why are we hearing so much nowadays about the benefits of electric heating? It’s because modern electric heating uses something called a “Heat Pump”, which provides heat in a completely different way, making it the most efficient way to heat homes there is. Through the miracle of physics, a heat pump is about 300% efficient! For every unit of energy you put into a heat pump in the form of electricity, you get about 3 units of energy out.

Well, how can that be, you ask?  To understand it, you have to remember that a heat pump is actually a PUMP, and it turns out it takes way less energy to pump heat around than it does to “create it” out of electricity or natural gas. Think about how a normal water pump works: it’s a law of nature that water always flows from someplace higher to some place lower, right? If you have water that’s in a low place — let’s say a well — and you want it to be in a high place — say a water tower —it’s never going to go there on its own. You have to consume energy with the pump to move the water to a place it kinda doesn’t want to be.

So, think of a heat pump as like, well, a pump… for heat. Yeah.

You see it’s also a law of nature that heat always flows from someplace hotter to someplace cooler. If it’s winter and it’s cold out and it’s relatively warm in your home, heat is never going to flow from the outside into the inside on its own. Similarly in the summer: it’s not going to flow from inside your home into the sweltering Davis summer conditions outside on its own. You have to consume energy with a pump to move that heat to a place … it kinda doesn’t want to be. See the pattern?

In fact, you probably already have something that’s essentially a heat pump: an air conditioner! Air conditioners supply cold air in the summer by extracting the heat from inside your home and pumping that heat outside. You’ve probably noticed that even when it’s hot outside, the air coming off the outside condenser unit is even hotter. So, it’s pumping heat from inside to outside (where it didn’t want to be).

Now, in the winter months, imagine that you flipped it around, so now the heat pump is extracting heat from the outside and pumping it inside where you want it. (Yes, there is heat outside, even when it feels pretty cold!) A heat pump space conditioning system is essentially a specialized air conditioner, that has valves so it can be run forwards or backwards—to provide heat or cooling, depending on what you need.

Now here’s the beauty part: heat pumps that use electricity from a renewable source (such as Ultra Green power from Valley Clean Energy) don’t burn any fossil fuel. Because no matter how efficient a natural gas furnace is, it consumes fossil fuel. As we know, fossil fuel is pumped from underground (where we want it to stay) up here to the surface to be burned in furnaces, which then pump carbon dioxide into the atmosphere (where we really don’t want it to be!).

So … we need to turn OFF that carbon pump and turn on the heat pump, all-electric heat pumps!

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Kristin Heinemeier is a mechanical engineer working for Frontier Energy, a local Davis company. She also serves on the Cool Davis board of directors and as chair of the program committee where she is very active with the Household Engagement and Home Energy campaigns. Kristin recently had air source heat pumps installed to heat and cool her home so now she’s lived the heat pump experience from all angles.

Kristin Heinemeier takes a break from her work studying energy efficiency in cooling systems. Photo courtesy Claire Black Slotton.

Heat pump incentives

TECH Clean California

New TECH program incentives are designed to dovetail with the existing Comfortable Home Rebate program through PG&E whose website shows both rebates side by side:

The featured photo for this article is the work of Cool Davis volunteer Yvonne Hunter. 

The featured photo for this article is the work of Cool Davis volunteer Yvonne HunterTechnician working on a new heat pump system. Photo credit Yvonne Hunter.

A contractor tests for heat loss using an infrared camera. Photo credit Kristin Heinemeier.