More than 30 years ago I lived in a Merrimack townhouse served by a heat pump and, boy, was I unimpressed.

Whenever it got too cold outside, the air from the vents was tepid at best, leaving us shivering. I was delighted when we bought a house with that New Hampshire staple, an oil-fired furnace in the basement.

But times change and so do technologies. Today, I’m looking to replace the furnace with a heat pump, and I’m not the only one.

“I find it very pleasant. I’m just as warm this winter as I was any winter before using the oil boiler,” said Pat Martin of Rindge, who is in her first winter with heat pumps.

Martin, a well-known environmental activist, is one of a half-dozen people who responded to my request for the experience of those who had used heat pumps in New Hampshire. I sent out the call because I’ve heard that the technology has improved and I wondered how they do in real-world use.

Note: I’m talking about air-sourced heat pumps. Ground-sourced pumps are much more effective but also much more expensive, and I doubt they’ll catch on much for homeowners.Electrify everything

Heat pumps are getting attention because one of the main slogans for those trying to reduce future climate change is to “electrify everything.”  Electricity can become clean in ways that fossil fuels can never be and electric motors are usually more efficient than internal-combustion motors – and heat pumps are more efficient than fossil-fuel furnaces, often by a factor of three or four. This is why Massachusetts wants to switch 1 million homes from oil or gas to heat pumps by 2030.

So what is a heat pump? (Terrible name, by the way). Just a machine with the same technology as a refrigerator. It absorbs heat in one place by condensing liquids, pumps that liquid somewhere else and then expands it to release the heat.

Most home heat pumps consist of an outdoor compressor that looks like a ground-mounted air conditioning unit, with tubes that go into the building carrying liquid or vapor, generally ending up in wall-mounted units called mini-splits (another terrible name). Those units blast out warm or cool air.

Cool air? One of their huge advantages is that the heat can be moved from indoors to outdoors or the other way around. In other words, they are simultaneously a furnace and an air conditioner.

As New Hampshire’s summers get hotter this is a big selling point, said Austin Atamian, who owns Atamian Heating in Greenland.

“A lot of people call and say hey, I’ve got baseboard hot-water heat and looking to add A.C. When I let them know they can use this for heat and save money. it’s usually a huge perk,” he said. “Generally people are in search of A.C. and the heat is a bonus.”

And before you ask – yes, modern heat pumps can keep us warm even in mid-winter, although they lose efficiency on the coldest nights and cost more to run. In case you doubt this, consider that they are very popular in Sweden, where winters are at least as gnarly as ours.

I admit it seems crazy that you can draw heat from the outdoors when it’s zero degrees but that’s because we use the Fahrenheit scale. Measure things in degrees Kelvin, which starts at absolute zero, and it makes sense: The record coldest ground temperature ever recorded in New Hampshire (minus 50) is still 227 degrees K, which leaves a lot of heat to pump.Not many responses

After my call for comments, I heard from a half-dozen heat-pump owners. I had expected more.  I’m not sure if this number is due to a rarity of heat pumps or an appeal that fell short.

All who responded were fans. The reaction from Nancy Hirshberg of Wolfeboro is typical.

“I got heat pumps this fall and it’s been great so far! Much lower cost than oil. And of course, I’m super excited for next summer when I will have cooling for those hot spells,” she wrote in an email.

Hirshberg is also an example, however, of unintended consequences. She didn’t realize how much she depended on wasted heat from inefficient furnaces to keep water pipes in her basement from freezing on “super-cold nights.” Now, she said, “I might have to put an electric heater in the basement for the future.”

Kiki Tidwell told of changing an 1840’s house in Portsmouth to all-electric service, including heat pumps. 

“All these heating guys said oh, you can’t do that, it’s not going to be warm enough,” she said.

But the result, said son-in-law Brendan Barker, proved them wrong. “The house is warm and toasty and we often only need to turn them on downstairs and the upstairs stays warm without turning anything on up there.”What about cost?

Right now heat pumps are generally more expensive to buy and install than oil or gas furnaces because of economies of scale if nothing else, but there are some subsidies available if you’re making the switch. Operating costs are generally much lower because they’re much more efficient, although swings in prices of fuels and electricity make it hard to predict how much you’ll save.

Martin is keeping track of heating costs in her 1,800 square foot house, built in the 1980s, compared to past years that involved just oil-fired hot-water baseboard heat, a system that is still intact and she says she has used occasionally for portions of the house.

Through December and January last year she used 153 gallons of oil, over that period this year she used 45 gallons.  At $2.87 a gallon that’s a saving of $415. Her electric bill for the two months totaled $405, compared to normal winter usage of $60 a month. Net result, she says, she has saved an estimated $131. That’s nothing to sneeze at, although it will take a long time to recoup installation costs of about $12,000.

Another advantage is the ease of installation compared to sticking a big furnace indoors plus oil tanks or gas hookup, and pipes carrying hot water heat or ducts carrying hot/cold air throughout the building.

“It’s a lot less invasive of an install vs. trying to find places to run ductwork in a house that wasn’t built for it,” said Atamian.

So what’s my conclusion from all this?

I’m definitely leaning toward a heat pump, partly to get the A.C. in the upstairs bedroom, which is sweltering on a few nights each summer, and partly because I have solar panels which will offset part of the extra load. (You can’t do that with an oil furnace.)

The cost won’t be trivial, like buying half a new car, I think. It’ll take a long time to recoup that from lower bills.  But I think it would be worth it in overall comfort (maybe I can sleep better in mid-July) and that warm glow of reducing the damage I’m doing to my kids’ future.

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