I’m writing this in the middle of the coldest week of January, the few days for which heating professionals design for, the time when homes push their heating systems to maximum output. Our team has already called each of our heat pump customers, talked though how their heating system will respond, answered lots of questions and let them know we are here if needed. In this article you will gain information essential for you to know before (and after) installing any heat pump in a cold climate zone.
Designers really do care that you’re comfortable in the coldest part of the year. If not, they will be hearing from you! Good design is peace of mind for them, and for you. It’s also a time of year where the level of service for each company shines or dulls, delivers or misses, succeeds or fails.
My advice is to be prepared with the knowledge of how these machines will or will not meet your needs when temperatures drop to extremely cold levels.
Designing for 1% and 99%
With our heat pumps living in the wild, we are keenly aware of their strengths and weaknesses, where cost battles with function in discussions, and how our customers affect heat pump performance.
Your heating system is a bit like a Peak Power Plant, which sits around all day, and only turns on when the Grid demands high power. It’s called Peak Power. As everyone returns home, they turn on all the lights run the laundry, cook dinner, open the fridge, plug in EVs and generally double the home energy demand.
Like Peak Power, the heat pump runs at 100% to meet your home heating needs. With very little heat outside, it works harder, less efficiently and non-stop to satisfy your thermostat temperature setting.
This extreme cold event is the 1% design. Equipment is designed to put out heat ample enough to satisfy your home’s heating requirements. To do this a temperature is chosen (the Design Temperature) and usually near 5 degrees Fahrenheit in the Front Range of Colorado.
The 1% design is a compromise, a cost vs. benefit result that leaves the 0.1% in question. In my mind it’s a reasonable approach, albeit sometimes leads designers to oversize your heat pump, a mistake that can lead to several other problems.
The other 99% of the year, your heat pump should be modulating, varying its output and singing quiet songs of high efficiency, energy savings and comfort unheard of from nearly any furnace.
The question for your heat pump designer is this: What is the design temperature of the heat pump system?
With this knowledge in hand, you will have a good sense that your design will or will not meet your expectations for performance 99% of the time. Furthermore, this tells you what your heat pump will consider as extreme weather, which happens 1% of the year.
Cutout Temperature
If there is one critical metric that is often hidden or overlooked, it is the cutout temperature of the heat pump system. Be advised it varies widely!
Cutout temperature is a hard setting in the heat pump or a soft setting on your thermostat, which when the outdoor temperature drops below, your outdoor heat pump system turns off to protect itself. While higher cutouts are typical in non-cold climate systems, it is incredibly important to know what any heating system will do when temperatures head south of zero. After all, these are life support systems.
Cutout temperature results in your heat pump stopping heating. It usually happens during the evening, and can be quite a surprise if you’re not prepared.
Preparation for a cutout of 0 degrees Fahrenheit for example may take the form of an electric heat strip kit, a fireplace burning, space heaters, electric blankets and sweaters or more creative solutions.
Ill preparation for cutout temperature often takes the form of no heat strip backup, no fireplace, no space heaters and all too often total surprise when the heat pump takes a break on the first coldest night.
We have seen cutout temperatures set as high as 40 F. On the other hand some can be much lower, well into the -20s F, and below any low temperature weather records set in decades.
Many times, the installer may not know the cutoff temperature of the equipment they are installing. This is due to the “close to your chest” proprietary information and choices of many manufacturers to obfuscate this information in the manual, leave it out of their trainings, and generally behave secretively about their equipment’s deficiencies in extreme weather. Of course, manufactures with very low cutout temperatures, or none, will be more forthright with this information.
In this case, you can give a bit of grace to your installer because they may need go ask a brand technical advisor. You can ask: What is the cutout temperature rating of your home heating system?
With that information, you can better choose the experience you’ll have 1% of the year.
Efficiency & Comfort
Oftentimes (the 99%) comfort and efficiency are synergistic. After all, the heat pump was designed, engineered and paired with your home to achieve lower costs and increased comfort.
However, in extreme weather, an electric heat strip runs at nearly twice the cost of the heat pump for the same amount of heat. However, during the few extremely cold days, that 1% of the year, the added install cost of the heat strip or running another heat supplement seems like a smart choice. In this extreme weather event, your home stays warm and comfy. Or perhaps the heat supplement shows itself as essential if your temperature droops in your home, and the design missed a key inefficiency elsewhere in your home, such as air leaks which magnify heat loss in extreme weather. Either way, you have the power to turn on or off the supplemental heat as you see fit.
This question is thus for you to ask yourself: What is my 1% cost, temperature and comfort level?
If your 1%, extreme weather tolerance is high, then you’ll have options for lower cost equipment and operation. If it’s low, then you will be happier with built in supplemental heat and a vanishingly low to nonexistent cutout temperature. See our article on dual fuel, supplemental and emergency heat considerations.
When the energy bill arrives, if it increases by a few tens of percent versus the month prior, remember that it’s cold out and your home needs more energy to keep warm. That’s the 1% cost benefit balance payment come due. And if designed right, that 99% of the year energy savings more than makes up for the 1% extreme weather event. If your bill is fairly flat through the extreme weather, then your home, heat pump installation, and how you use it are ideal.
Got questions about extreme weather operation of heat pumps? Drop us a line and we will be happy to answer!
