The Pros and Cons of Heat Pumps

by Erik North on June 13, 2017

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What is a Heat Pump?

Heat pumps are all the rage in Maine’s efficiency community in recent years. Efficiency Maine, the organization that, you guessed it, runs energy efficiency programs in Maine, has issued more rebates and loans for heat pumps than all other qualifying measures combined. But what exactly is a heat pump and why are they so popular?

A heat pump is a very efficient way to heat and cool your home year round. They are comprised of an exterior condensing unit that looks like a box fan and an interior evaporating unit connected to one another with a refrigerant line. Well, what does all that mean?

Also, we’re talking about air source heat pumps here. An air source heat pump is one of those things that you know how it works, you just don’t realize it. Without getting overly technical (which we’ll do in a later article), the mechanics of a heat pump are identical to those of a refrigerator. Have you ever felt the back of a refrigerator, which can get very warm? A refrigerator takes the air from inside it, extracts the heat, vents the heat out the back and blows the now colder air back into the case.

A heat pump works more or less the same way. It takes air from outside the house, extracts the heat from it, and either sends warm or cool liquid down the refrigerant line to warm or cool the house.

What are the Pros and Cons of a Heat Pump? – Pros

Low Cost/Efficient
Let’s hit the two big pros first: Efficiency and their ability to heat and cool. Heat pumps are very efficient. They are electric but are 3x efficient or more than standard resistance electric coils (basically every other type of space heater). If electric prices were $0.15 per kilowatt/hour (about current prices in Maine), that translates to about $1.40 per gallon of heating oil.

A/C and Heating
The second biggest pro for heat pumps is that despite the name, they both heat and air condition. This allows you to maintain comfortable, even temperatures year round. While cooling isn’t as big a concern in Maine’s climate, if maintaining a consistently comfortable living space, no matter the outside conditions, heat pumps work great.

Heat pumps also allow a degree of control and ability to adjust temperatures that standard air and hot water systems can’t easily match. While a hot air furnace can blast hot air through their ducts, rapidly heating the living space, they don’t heat the space very precisely. They will very rapidly get you from 50 F to somewhere around whatever the thermostat is set to. A heat pump can regulate it’s temperatures much more precisely.

Compared to the rumbling beast found in the basement of most homes, a heat pump is very quiet. Most people report that after a few days, they forget it is even there.

Again, compared to an oil or gas fired system, the heat pump comes out ahead. Mass produced electricity has a smaller carbon footprint than an oil or natural gas burning unit on site. Add the aforementioned efficiency and that electrical generation is moving toward more renewables, means that heat pumps are a green answer to heating moving forward.

Low Maintenance
Like your refrigerator, you only need to periodically need to clean the filter and have your HVAC pro do a check up.

Better Performance at Low Temps
A big knock on heat pumps in the past has been their inability to perform at low temperatures. Once the temperature got too low, they couldn’t extract enough heat to keep up with the needs of the house. However, modern heat pumps use updated technology that makes it much less of an issue.

What are the Pros and Cons of a Heat Pump? – Cons

Efficiency Drops with Temperature
Getting into the drawbacks, one is that the efficiency does drop with the temperature. While the new technologies allow the system to function at lower temperatures, there still isn’t much heat in the air. Less heat means more times the air must run across the compressor coils to extract the same amount of heat.

Movement of Heat
Another con is that heat doesn’t move particularly well around heavily partitioned spaces. So if you have a house with many rooms, that means those rooms may not warm up very well.

Primary Heat Source
Heat pumps do an amazing job as a supplemental heat source, but not quite as well trying to heat the entire home. If you have a house with many rooms, you need to put several interior units to ensure enough coverage. Which leads to…

If you want to heat/cool an entire building with heat pumps, that means several interior units. Several interior units can be very expensive. Installing four interior heads with a properly sized exterior condensing unit can be more expensive than a new oil or gas boiler.

There’s a lot to consider with heat pumps, but they can be a great addition to many homes, especially if you heat and air condition.

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