What Size Heat Pump Is Right for My Portland Home?

In the market for a new heat pump? If you’ve done any research, you’ve probably noticed that heat pump systems come in many different sizes—and you might be confused on which size to get.

Four Seasons is here to help.

In this article, we’ll walk you through:

  • How heat pumps are measured
  • Why proper heat pump sizing is important
  • How to get the right size heat pump

Need quote to install a heat pump? Call us at 503-538-1950 or schedule an appointment online. Four Seasons will make sure you get a system that fits your home perfectly.

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How heat pumps are measured: BTUs & tons

Heat pumps aren’t measured by their physical size, but rather by how much heat they can move into or out of your home.

Heat pump capacity is measured in 2 units:

  • BTUs (British Thermal Units): One BTU is the amount of heat required to heat one pound of water 1°F, or approximately the amount of heat generated by burning a single match. Most residential heat pumps typically range from 12,000–60,000 BTUs.
  • Tonnage: Tonnage (also called “ton”) is another measurement of heat energy. One “ton” is the amount of heat needed to melt one ton of ice in 24 hours. One ton is equivalent to 12,000 BTUs, so residential heat pumps range from 1 to 5 tons.

Now that you understand how heat pumps are sized, we’ll go over why it’s important to get the size right.

Getting the right size heat pump is important

Think about buying a pair of shoes. You get the pair that fits just right because shoes that are too big or too small can cause problems, right?

The same principle applies to buying a heat pump: You need a system that fits your home perfectly, otherwise you’ll see problems (expensive ones) down the road. We’ll explain.

A heat pump that’s too small will run constantly without ever being able to properly heat or cool your home. It’s small capacity won’t be able to keep up with the demand.

A heat pumpthat’s too big will “short cycle”, which is when the unit turns on, heats/cools your home too quickly, then shuts off.

In both situations, an improperly sized heat pump can cause:

  • Higher energy bills. Undersized heat pumps will run longer—and consume more electricity—than they’re supposed to. While a heat pump that’s too large will turn on more frequently, which requires a lot more energy than starting up and running a regular cycle.
  • Inconsistent temperatures. Because an oversized heat pump only runs for short periods, it doesn’t have time to heat/cool every inch of your home. This also makes your home more humid because it won’t run long enough to remove the moisture.
  • Shortened heat pump lifespan. The starting and stopping of oversized systems and constant running of undersized systems causes parts to wear out quicker than normal.

So, how do you get the right size heat pump for your home? You need a professional to perform a heat load calculation (also called a Manual J Load calculation).

How to correctly size a heat pump: heat load calculation

A heat load calculation is a complex set of measurements that determine how quickly your home loses heat.

When performing a heat load calculation, a tech will look at factors like:

  • Square footage and layout of your home
  • Number, size and orientation of windows and doors
  • Height and size of rooms
  • Climate conditions of your area
  • Quality of your home’s ductwork and insulation
  • Amount of shade your home gets
  • Type of roof and flooring
  • And many more factors

Because a heat load calculation is so complex, it’s best to leave the work to a trained professional who will have the proper tools, software and know-how to accurately determine what size heat pump you need.

Now that you understand the complexity of sizing a heat pump, we’ll leave you with a warning: Don’t trust a tech who gives you a generic recommendation based on the square footage of your home.

As you saw above, square footage is just one of many factors that impact how quickly your home loses heat. Recommendations based on square footage are bound to result in an improperly sized system.

Need help finding the right size heat pump?

Give us a call at 503-538-1950 or schedule an appointment online. One of our techs will calculate the right size heat pump for your home, and work with you to find one that fits your budget.

Schedule service