How Does a Heat Pump Work in Cold Weather?

September 18, 2014

A heat pump is basically an air conditioner that can work in reverse to heat your home in cold weather.

An air conditioner that heats?

Nonsense!

Oh, but it’s true.

So how the heck does it work?

We’re glad you asked. 

It’s just like cooling your home, but in reverse

To understand how a heat pump heats a home, you need to understand how it cools a home because it just reverses the cooling process.

Here’s what we mean:

An air conditioner/heat pump does not just “blow cold air,” it absorbs heat from your air.

Imagine this: To cool a home, an air conditioner/heat pump works like a “heat sponge”:

  1. First, the refrigerant in the inside unit absorbs heat from your air.
  2. Then the now hot refrigerant flows to the outside unit and disperses the heat so the refrigerant can flow back inside and absorb more heat from your air.

It’s similar to how you’d use a sponge to soak up water and then squeeze it out so you can use it to soak up more water.

So now to answer the original question: How does a heat pump heat a home in cold weather?

Once you turn a heat pump to “heat mode”, it reverses this absorption process using a reversing valve. Now the outside unit absorbs heat from the outside air and moves the heat to the inside unit, allowing it to heat your home’s air.

That’s a super simplistic way of looking at it, but that’s the basics.

"But I heard heat pumps don’t work efficiently in extremely cold weather!"

You heard right! At 40 degrees, heat pumps struggle to absorb heat from the outside. So the inside unit uses a backup electric heat strip (like the ones in your toaster) to assist heating your air.

But this electric strip is a ginormous energy gobbler (it’s not very energy efficient). So a heat pump would seem like it’s not a good choice for heating a Kansas City area home, right?

Not necessarily.

Heat pumps can be paired with a furnace in what’s called a “dual fuel system.” That’s a fancy way of saying the furnace kicks on instead of an electric heat strip when the weather gets below 40 degrees.

So a dual fuel system lets you have the heating energy efficiency of the heat pump with the reliability of a furnace. 

Want to learn more about heat pumps?

If you’re thinking about having a heat pump installed, check out our article HSPF: A Rating You Need to Weigh When You’re Buying Your Heat Pump.

To learn more about heat pumps in general, read energy.gov’s heat pump article.
 
Or contact us with your questions.
 
Santa Fe Air Conditioning and Heating serves the Kansas City area.


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