This article first appeared on Grist.org.
Q. Dear Umbra,
I want to replace my aging gas furnace with a heat pump. But the heat pump is much more expensive than a high-efficiency gas furnace, and I’m only gonna spend the money if it cuts down on greenhouse gas emissions. And heat pumps use HFCs, which are potent greenhouse gases themselves, and some of them probably leak during manufacturing and installation. Should I spend the money on improving my insulation instead?
Ken
Corvallis, Oregon
A. Dearest Ken,
Somewhere in the world, there must be a place where it’s a steady 68 degrees at all times. The locals must feel completely comfortable in every season, never stress over all the oft-confusing options for home heating and probably get free ice cream every week too. What a charmed life that must be. For the other 99.99 percent of us, there’s at least some wrangling to be done over the heating and cooling of our homes (not to mention all the ice cream budgeting we must do). Now that the cold season is upon us, let’s untangle your options and get you toasty — without doing the same for the planet.
I’ll address your last question first: Should you upgrade your insulation instead of your furnace? Ideal answer: Do both! It’s a very smart move to button up your house as tightly as you can before making any major heating system changes. The less warm air that can escape from your home, the less energy any system will use. Investing in a spendy new system without sealing doors and windows or beefing up insulation is kind of like having a car that runs on clean biodiesel but has a gas tank riddled with tiny holes. Not exactly what you’re going for, is it? So first things first: Head over here and here for some tips on upping your home’s efficiency.
That said, Ken, an aging furnace can certainly be beat with today’s ever-improving heating technologies, so I’m glad you’re thinking about making an upgrade. If you have the scratch to spend up front, you’ll ultimately save both money and carbon emissions by breaking up with your less-than-efficient old furnace.
I’ll tell you from the get-go that there’s no definitive winner in the greenhouse-gas faceoff between high-efficiency gas furnaces and heat pumps. Far too much depends on the efficiency of the particular model you buy, the local climate, your area’s power grid, and how well you maintain the system. So before you sink any money into this shake-up, consult a qualified heating/cooling pro for a better idea about how either option would work for you.
With that in mind, though, it’s a good idea to consider that heat pump. Not that switching to a high-efficiency gas furnace is a bad move — it isn’t. Today’s furnaces can be up to 98.5 percent efficient, a huge improvement over yesteryear’s numbers of 56 to 70 percent. In fact, upgrading to a better furnace can slash your fuel costs and your carbon emissions in half, perhaps giving you such a warm, fuzzy feeling that you can even dial your thermostat down a little.
Heat pumps, on the other hand, tap naturally existing heat in the air or ground — not fossil fuels such as natural gas or oil — to cozy up your castle. Basically, they use a little electricity to move warmth from the outdoors (yep, even in the winter) inside; in summer, they work in reverse to cool the place. We like ‘em because they’re much more efficient than any furnace: An air-source heat pump uses 50 percent less energy than an electric furnace or baseboard heat, and a ground-source model is up to 45 percent more efficient than its air-source cousins. In fact, for every unit of energy they use, heat pumps produce three to five units of “free” heat. You can even link your system to the hot water heater and use that excess warmth to power your shower. In theory, heat pumps can be your ticket to 100-percent renewable heat — provided your electricity comes from totally green sources.
Alas, the pump isn’t perfect. As you well know, Ken, they’re more expensive than a new furnace. (Though government tax credits can help offset the cost; you can still get this 30 percent federal credit through the end of 2016, and the state of Oregon has one too.) Lower energy bills will eventually put you ahead, but it can take five to 15 years for the system to pay for itself (less if you’re replacing your air conditioner at the same time).
Another issue is that heat pumps still use electricity, which, depending on where you live, might be provided by dirty coal-fired plants or other nonrenewable fuels. This, plus your local climate (pumps work best in milder areas), matters a lot in terms of which heating system will be best for lowering your overall carbon emissions. One analysis found that high-efficiency gas furnaces had lower carbon footprints than the best ground-source heat pumps in very cold regions and places with carbon-heavy electric grids. But in green-power zones and more moderate climates — like yours in Oregon — heat pumps are better.
One more wrinkle: those hydrofluorcarbons (HFCs) you mention. These very potent greenhouse gases are used in heat pumps and refrigerators, and there’s some concern that HFCs are released during manufacturing, use, and disposal. One analysis calculated that these emissions add 20 percent to a heat pump’s carbon footprint; others argue that a properly installed system shouldn’t leak, and proper disposal helps prevent too many HFCs flying off into the atmosphere. Another study out of the U.K. crunched the numbers and found heat pumps still reduce carbon, even considering HFCs. The final answer remains murky. Meanwhile, new non-HFC pumps (some using ammonia) are beginning to gain steam.
I hope I’ve given you enough to start your own personalized analysis: I do think a heat pump could be a smart, green choice for you, but do look closely at the variables. Either way, upgrading from your dinosaur furnace will be a big step up — consider it an early holiday gift to yourself, and all the rest of us.
Geothermally,
Umbra
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