Despite adding air conditioning, heat pumps will slash apartment building’s electric bill

Published: 2/28/2022 4:44:22 PM

The electric bill at 116-unit Crutchfield Apartments near the State House is about to be slashed because the building has switched from electric baseboard heating to modern heat pumps, despite the fact that the change also brought air conditioning to the apartments for the first time.

“We still expect to cut out kilowatt usage by half, even with those AC units,” said John Hoyt, who oversaw the change as executive director of Concord Housing, which owns the public building at 15 Pitman St. near the Merrimack County Superior Court. “We’re trying to do everything possible to cut our costs down.”

The transition cost about $940,000, covered by rebates from the electric utility Unitil through the NHSaves Low Income Weatherization program. The building will save more than 282,408 kilowatt hours per year, or more than $100,000 on electric bills depending on future rates.

That saving reflects why heat pumps are touted as a major method of reducing the future effect of climate change. They allow buildings to be heated and cooled using much less energy than other systems.

Heat pumps are a variable refrigerant flow heating and cooling system. They don’t create heat like a furnace but move it from one place to another via liquids, just as a refrigerator does. When the heat is moved indoors then the wall-mounted units warm the air; when the heat is moved outdoors, they act as air conditioners.

Installing new heating systems isn’t always straightforward in existing structures, although heat pumps require less work than forced hot-air or hot-water heating systems. Crutchfield Apartment was built in the 1970s from prefabricated modules made of concrete, each about the size of a railroad car, which complicated things.

“There’s only so much you can do in a concrete building,” said Hoyt, who stepped down as executive director last month.

A half-dozen large compressors were hoisted to the top of the seven-story building, one block away from the State House. Holes were drilled down in three places – the end of each wing and in the center of the building, to hold pipes carrying refrigerant into the building. Tubes were run in boxes along the hallway ceilings, splitting off the wall at each apartment to serve a unit known as a mini-split.

“We ran tubing just above the kitchen cabinetry so you couldn’t see it,” said Hoyt.

The total installation took five months and was done in stages to limit disruption to residents.

The savings at Crutchfield is notable because the previous system of resistance heating uses a lot of electricity. The monetary savings over gas or oil furnaces would be less, although it would still happen.

Hoyt said Concord Housing looked at putting heat pumps into another building that uses natural gas furnaces but the payback period was too long for the project to get support.

The Crutchfield project was undertaken and managed by Resilient Buildings Group, a Concord firm that designs and buildings energy efficiency and conservation projects.