We have never had backup heat before. Why do we need it now, all of a sudden? And what in the world is supplementary heating? Isn’t the coldest night the worst time to run electric strip e-heaters? I’m buying a heat pump not a toaster oven!
My heat pump wasn’t installed with any backup heat or supplementary heat. But my house also dips in the coldest nights of the winter, so I get it. But my home also leaks like crazy. That’s my real problem, and showed up as a low energy audit score.
Thanks to our ability to do home energy audits in Just Heat Pumps, we measured my hourly air exchange rate a 10.56. I’ve got a long way to go to fix that problem! But, my already expensive winter bills would skyrocket with a toaster heater running to keep up with the huge heat loss. What’s the balance point, or sweet spot?
In this article, we explore backup heat and supplemental heat when designing a heat pump system. Spoiler: My opinion is to keep it simple, save money, stress on the grid, and reduce emissions when it matters most.
Backup Heat Increase Costs
Two costs increase dramatically with back up heat: 1. Another heating system (electric strips or gas fired) is strapped onto the heat pump. Double double with cheese please! 2. The added costs of operating and maintenance, called O & M in many businesses. Think of this a heating home economics 101. Two heating systems for twice the O&M!
With the recent landing of heat pumps in the US, backup heat has found its way into too many heat pump quotes, bids and proposals. Here’s the thing, backup heat is a total red herring. It’s not needed in most cases. Only a heat pump that is well designed to match your home’s heating needs is all it takes.
Blackouts Shut Off Backup Heat
Backup heat does not work during an electrical outage. Neither the fan or board in the gas furnace nor the electrical strip heater can run without electricity. Backup heat indeed!
A true emergency heat plan is actually what is needed, in the event of blackout or extrene winter conditions.
Supplementary Heat is Not necessary. Think fireplace, kerosene or other very simple, no nonsense form of heat. That’s what you’ll need when the power goes out, that or a friendly neighbor with a fireplace or other emergency heat plan.
Supplementary Heat Adds Costs
Supplementary heat is another expensive add on. Although there’s a substantial point to consider for including it. In the coldest nights of winter, an electric or gas supplementary heater can add BTUs to your heat pump’s total heat output, and makeup for the colder derated capacity.
Even a cold climate heat pump under 100% operation will move less heat into your home when there is less heat available in the air. The least expensive method to accommodate for extreme cold heat pump derating is included in the design of the system.
Matching your home’s heat load and the derated heat pump heating capacity at 3 degrees Fahrenheit (or 5 deg F) in Denver ensures that nearly all of the hours your heat pump runs, it will meet your home’s heating needs. A few days of negative temperatures, and one or two extreme cold days are the only time your home would feel chilly.
Supplemental Heat Is Optional
If the heat pump were undersized, supplemental heat is therefore a personal decision. And there’s advantages to undersizing vs. oversizing. But the key point is to RIGHT size the equipment to meet your home’s heating demand on those cold nights as well. This is easy. Just ensure the heat pump design will meet 100% heating demand on those extremely cold nights.
A well designed system will under perform just a few hours per year, perhaps ten. The variable motor speed and compressor output will modulate the heat the rest of the relatively mild winter.
Choosing to not include supplemental heat reduces the install costs and the O&M. An electric strip heater requires added equipment and a larger electrical circuit at greater install price. The, gas supplemental heat requires added equipment, install costs and regular maintenance.
If the heat pump were actually to fail, the gas or electric would run full time, and you may never know till those extreme cold nights when you ONLY have the limited supplemental heat.
Here the backup and supplemental heat problems are similar. If your heat pump install was less than good, then you might be running for years on the backup or supplemental heat only, never the wiser.
Signals of A Poor Design
If you are planning to include backup and/or supplemental heat, be sure that your thermostat can communicate any ERROR messages. The smart thermostats are notorious for not communicating error messages, due to proprietary control software and optimization systems.
Go with the same name brand as the equipment, and ask if this feature is included. We often include supplemental heat with this key design point in mind.
A simple RIGHT sized heat pump design is better, cheaper on your wallet, will use less energy and going to save the planet faster. Save the planet faster how, you might ask? By using less materials (mining, processing) and reducing the need for peak power plants (gas fired) which are only used a handful of days per year to meet peak power demand, peak power which is increasing when all the toasters are ON during extreme weather.
Summary
The two key points to remember are: 1) backup heat is not needed in most cases, and usually employed as a major fudge factor for a poor design. 2) supplemental heat is optional, and should be approached with caution. That caution and request for a properly designed heat pump for your home can save you money, and help the planet.
Got questions? We love those! Contact us here.