The age of the air source heat pump
By Tux Turkel
Transformational.
That’s a word to describe the heating transition in Maine a half-century ago, when home-owners started saying goodbye to their coal bins and hello to oil tanks. Compared to coal, oil was cleaner, more convenient and more efficient.
In 2015, we may be on the cusp of another transformation in the way Mainers warm their homes. This period may be remembered as the age of the air-source heat pump.
This may be the era when the oil tank that was the dominant fuel source in the majority of Maine homes since the 1960s gave way to an outdoor metal box with an electric fan, a device connected to living space only by wires and refrigerant lines. The box grabs warmth that’s present but hidden in frigid winter air. In summer, it reverses the trick to pull oppressive heat and humidity from inside the house.
And although a heat pump uses electricity, the fact that it’s only transferring heat and not burning a fuel creates very high operational efficiencies, typically 200 to 300 percent in the winter. For every unit of electricity used, two or three units of heat are produced. That makes heat pumps just about the cheapest way to warm a home today in Maine, on par with firewood and less costly than natural gas and oil, according to Efficiency Maine comparisons.
In the last two years, more than 9,000 air-source heat pumps have been installed in Maine homes. They can be spotted at subsidized housing projects and million-dollar mansions. Concealed from view, an array of heat pumps is set behind the historic Blaine House, the residence of Maine’s governor.
Heat pumps may be right for the Blaine House, but are they right for your house? Increasingly, the answer is yes.
Refinements in performance and installation techniques now are expanding the application of heat pumps, making them a good fit for more situations. A few years back, air source heat pumps were mostly considered a supplemental technology in Maine. The efficiency of heat pumps goes down as the air temperature drops, and earlier versions just didn’t function well enough to rely on in bitter cold. It still may be prudent to have a back-up heating system for the coldest days. But improvements are turning heat pumps into primary heat sources, even in cold-weather climates where the mercury can settle well below zero.
“I think we’re just scratching the surface,” says Dana Fischer, residential program manager at Efficiency Maine, the state’s energy conservation agency.
Fischer is a big fan of air-source heat pumps. He often makes the coal-to-oil analogy. But he also urges caution. Heat pumps have become so popular that it seems anyone with a pick-up truck and ladder is installing them. Efficiency Maine lists 423 vendors and 60 heat pump models that are eligible for $500 rebates.
Do your homework, Fischer advises. Get multiple quotes. Ask for references. And look for experienced vendors, using a search tool on Efficiency Maine’s web site that lets you find installers near your home who have done the most installations.
And consider tightening up your home, so that you’ll need a smaller heating unit and use less electricity. Efficiency Maine offers a $100 bonus for homeowners who do air sealing with an energy assessment, which qualifies for a $400 rebate. Taken together, there’s $1,000 available for installing a heat pump and sealing cracks and air leaks.
Many Mainers by now have heard of air-source heat pumps. They’re often called “mini-splits,” because the outside unit is separate, or split, from the indoor unit. People also refer to them as “ductless” heat pumps, because the conditioned air is circulated from the inside unit, not from a network of ducts, like on a central heating or air conditioning system.
The concept of direct heat is familiar in Maine. Thirty years ago, homeowners struggling with high bills started installing Japanese-made, direct vent heaters.
These units, pioneered by Rinnai and now-defunct Monitor, used kerosene to generate heat right where it was needed most. Tens of thousands were installed in Maine, and they’re still common fixtures in kitchens, living rooms and that hard-to-heat den in the ell. Today’s leading air-source heat pumps popular in Maine also feature Japanese technology, this time by familiar industrial giants such as Fujitsu and Mitsubishi.
And unlike the old kerosene heaters, today’s heat pumps are capable of warming more than just one room or one floor. Whole-house installations now are available for heat pumps that circulate air through a series of ducts spread around the house, connected to one outdoor unit. Sometimes, single and multiple units can be installed in tandem to achieve whole-house comfort.
This two-system approach was put in place earlier this year at a home in Falmouth. The installation highlights what’s possible today with heat pumps.
When the owners decided to upgrade their home’s heating and cooling systems prior to a renovation project, they faced a choice. The home is large, measuring more than 4,700 square feet on two stories.
One thought was taking advantage of new natural gas lines that were coming to the neighborhood. Also in the mix was a wood pellet boiler, or just staying with the existing oil boiler and installing central air conditioning in parts of the 42-year-old, contemporary style home.
But a heat pump offered a climate control system that’s much cheaper to run than oil in the winter and has the bonus of cost-effective humidity control and air conditioning in the summer. The old oil boiler could remain functional for backup, and for heating water.
Ann Goggin, president of Goggin Energy, stands in front of a new heat pump installation on a house in Falmouth. The units are installed high on brackets to be out of the snow, under the eaves to protect from ice damage and behind a bush to hide them from view. PHOTO: TUX TURKEL
That was the solution proposed by Ann Goggin, who is president of Portland-based Goggin Energy. The company installs solar panels and performs energy audits, but today, 80 percent of its business is heat pumps. Three quarters of customers want the systems to become their primary heat source.
“I really believe that in the next five years, we won’t see a house built that doesn’t have a heat pump,” Goggin said. “They make so much sense.” (Learn more about how heat pumps work).
Goggin acknowledges that heat pumps won’t be the primary source solution for every home. Natural gas may make more sense in a very large house where air conditioning isn’t a priority, she said. And homeowners who have a late-model oil boiler may find it economical to convert the burner for natural gas.
Another emerging option is heat pump central heating. Goggin carries the Daikin Altherma, which can transfer heat from the air to water for radiant floors and baseboards. But the unit is expensive and doesn’t raise water temperatures high enough to work well with existing baseboards, Goggin said. A model sold in Europe that can produce 160-degree water temperatures soon will be exported to the United States, she said, providing an alternative for homes with forced hot water heating.
With any heat pump alternative, people want to know what a system will cost and when their investment will pay for itself in fuel savings, typically compared to oil. The answer depends, based largely on the size of a house, how well it’s insulated and air-sealed and future projections for the price of oil.
For example, Goggin recently completed a whole-house project in Portland that cost $13,000, after the Efficiency Maine rebate. If oil prices remain low, as they were last winter, the simple payback would be nearly eight years. If oil prices shoot up to levels seen in 2013, then payback would be closer to five years.
As another example, a single mini-split unit meant to heat the first floor of a two-story home on Peaks Island costs $3,501, after the rebate. Depending on oil prices, the simple payback could range from more than six to less than four years.
PHOTO: COURTESY OF MITSUBISHI ELECTRIC
At the Falmouth home, the owners had paid more than $5,000 for heat and hot water last winter and burned 1,632 gallons of oil. The heat pump system, which cost $10,700 after the rebate, was designed to meet at least half the home’s heating needs. It’s expected to save between $1,271 and $1,873 a year, based on oil prices over the past two years. The projected payback is between six and eight years.
Outside, two Fujitsu condensers are mounted side by side on the wall. Installation details are important. Efficiency Maine’s best practices require the units to be at least two feet off the ground, out of the snow. If they are under the drip line of a roof eave, they must be protected with a rain cap, to prevent ice damage.
The installation hits those marks. Raised on brackets and tucked under the eaves, the condensers are protected. As an added bonus, they are hidden behind a small tree on the side of the house.
One of the condensers, which is rated to -15F, is connected via refrigerant lines and control wires to a wall-mounted unit in the downstairs den. It will heat and cool that area. The other condenser is rated to -5F and is connected to a “compact duct” unit mounted in the attic. It will heat and cool the kitchen and living room, via short runs of insulated ductwork that connect to grilles in the ceilings.
By using two units, the house will have more heat output at lower temperatures that with a single “multi” unit, according to Goggin. Using the compact duct and grilles solved two problems. It was hard to find a good place for a wall-mounted unit, and the homeowner preferred the look of the discreet ceiling grilles upstairs, rather than the wall mount.
The downstairs unit, along with the existing oil boiler making hot water, should eliminate any worry about freezing pipes on the coldest days. Goggin recalls a client in Brunswick who had two heat pumps installed, in a home with a poorly-insulated basement. Goggin suggested fixing that, but the homeowner decided to put it off for a year. Without the oil furnace running, though, the basement got very cold.
“They never had to put the oil heat on again, but the pipes froze,” she said.
Beyond frozen pipes, reducing heat loss just makes sense in an overall strategy to cut home energy bills. That’s a message given by Central Maine Heat Pumps, which has offices in Benton and Falmouth.
Dawn Marin, part of the sales team, said homes first get a basic energy assessment to spot insulation gaps and major air leaks. Estimator crews perform a blower-door test, using a machine that helps measure air changes per hour. Central Maine has a sister company, Advanced Spray Foam, so it can also offer insulation services.
Homeowners are made aware of the Efficiency Maine bonus rebate. Most customers take advantage of it, Marin said, because a tighter house can reduce the size and cost of the heat pump installation and increase its performance.
“It makes a really large difference in how they will work,” Marin said of cutting heat loss.
The refinement of heat pumps also has created a new synergy with renewable energy, notably solar electric panels. Homeowners with a south-facing roof or open field can install photovoltaic panels with enough output to power a heat pump. It’s a great concept: run your electric heating system on sunshine. But in practice, there’s more to the picture.
First, PV panels in Maine generate most of their power in the summer. On a cloudy winter day and at night, you’ll still need power from the grid for your heat pump. Under Maine law, utilities credit your bill for the solar power you generate. So by banking credits in the summer, the overall electric bill will be much lower. This arrangement is called net metering.
Still, there are many winter days in Maine when sunshine can run heat pumps.
A solar array consisting of 51 PV panels powers a heat pump, hot water heater, a Chevy Volt electric vehicle, as well as the household electricity supply at the 2100 sf home of Mike and Louise Tabone. Their total bill for heat, hot water and electricity was $283 last year. PHOTO: COURTESY OF MIKE TABONE
In Oakland, Mike Tabone has 51 PV panels on his 8-year-old Cape-style house. Even on a cold but sunny day, they can feed his Fujitsu heat pump, with power to spare. That extra output can go back to the grid, or help run his 60-gallon General Electric hybrid water heater, essentially an air-source heat pump that warms domestic water.
Tabone, a retired engineer, invested in an oversized PV array to satisfy 90 percent of his energy needs. It cost $34,000. But at today’s oil and electric rates, he figures the investment will pay for itself in seven years. And last year, his total bill for heat, hot water and electricity was $283.
Tabone says he’s happy with the set-up, but if he were starting from scratch today, he’d prepare for getting off the grid completely.
“If I could do this again,” he said, “I would put the required interconnections for a battery storage installation in the future, once I was convinced that the battery technology was cost effective and applicable.”
For most Mainers, though, heat pumps are fast becoming the heating source of choice to get away from the volatility of oil and the expense of propane. Any doubt that these devices are well suited for Maine’s climate should be eased by looking at the experience in Atlantic Canada.
In Nova Scotia, Fischer said, Efficiency Maine’s counterpart has been offering rebates for roughly 24,000 heat pumps a year.
“I think we can get there,” Fischer said of converting Maine homes. “I do think this is as transformational an event as going from coal to oil.”
Related article: How a heat pump works
1 Comment