When the summer temperatures climbed, it not only got hot in Rob Amrein’s two-bedroom apartment, it got cacophonous. “We had three window air conditioners and it got pretty noisy,” he said.
It also got expensive with electricity bills for some months tripling, reaching as high as $170.
Those days are gone. Now on a hot day there is only a gentle “whoosh” of a fan and potentially lower energy bills thanks to the installation of an energy-efficient heat pump under Denver’s commercial and multifamily building electrification pilot program.
The aim of the pilot is to help the city’s Office of Climate Action, Sustainability & Resiliency to gather data to better set rebates and incentives for heat pumps, said Mac Prather, the office’s residential energy efficiency administrator.
So far, 64 properties have applied to the $7.5 million pilot program with eight projects moving ahead with installing equipment. Program participants include retail stores, office buildings and multifamily apartments buildings.
And that is how Rein’s garden apartment complex in the city’s Sunnyside neighborhood found its way into the pilot. Since the rents for the units were below market, the project was in line for extra funding from the city.
“I got a notice from Denver about converting from natural gas to heat pumps and it caught my eye,” said Bret Anderson, the owner of the six garden-apartment complex. “Since the rents were below 80% of typical market rents it qualified as an equity priority for the city’s program.”
Anderon hired Denver-based Elephant Energy to install the heat pumps and the installer put together a package of rebates from the city and Xcel Energy that covered the entire $153,000 project.
That included $120,000 from Denver, $24,000 from Xcel Energy and $9,000 in heat pump discounts from the state.
“To be energy efficient, a home ought to be weatherized as well,” said Bobby Foley, Elephant Energy’s head of sales. “We contacted Energy Outreach Colorado, whom we work with, to insulate the units.”
Energy Outreach Colorado, provides a range of energy-related services to low-income households including help paying bills. One of those services is a multifamily energy efficiency program, which administers federal weatherization aid.
The program weatherizes 30 to 50 buildings a year across the state, according to Kelsey Engelking, agency’s multifamily program manager. For the garden apartments heat pump project, the energy efficiency program provided $14,716 to insulate the roofs.
An “air source” heat pump moves heat. It can move it from the outside to the inside when it is cold and from the inside to the outside when it is hot.
How? A refrigerant, with a low boiling point, something like 55 degrees below zero, runs through a pipe exposed to the outside air and even a little bit of heat vaporizes the refrigerant.
The vaporized refrigerant, with the heat, goes through a compressor — squeezing the air and raising the heat to about 105 degrees as it is moved on into the house.
The refrigerant, once again a liquid, is sent back outside to pick up some more heat. In the summer the process can be reversed, moving heat from inside to outside, cooling the house.
Elephant Energy outfitted each apartment with a new electrical panel and a Mitsubishi heat pump, rated to work even at 13 degrees below zero.
“Two things we wanted to make sure was that we sized the heat pumps appropriately and that the ducts will work,” Foley said.
The apartments had gas-fired furnaces and the ducts are often smaller for a gas furnace than what would be used for a heat pump. To make sure, Elephant Energy crawled in to check the ducts.
“The major concern for the residents was to get cooling,” Anderson said. “They had a hodgepodge of window air conditioners, portable ones and fans.”
Unlike an air conditioning unit, which kicks on and then off when a thermostat hits the desired temperature, “the beauty of the heat pump is it moves more air over time,” Foley said. “Set it and forget it, it is working all day.”
Amrein agrees. “You really don’t hear it and it’s been comfortable,” he said. The heat pump had only been operating for three weeks so Amrein said he didn’t yet have a sense of what it will mean for his electricity bill.
“My estimate and the city’s estimate are that the bill will be about the same,” Anderson said. “If they were cooling with AC, it would be less. … We do expect it to be positive on the bill for the most part.”
“It definitely wouldn’t have happened without the aid of the Denver program,” Anderson said.
Denver is offering rebates for a variety of heat pump technologies, including ground-source heat pumps, which pull their heat from below ground, and rooftop heat pumps.
“We continue to see increased enthusiasm and participation as time goes on,” Emily Gideon, a spokeswoman for the city’s climate office, said in an email. “As a result, if a Denverite — a single-family homeowner or 20-story building owner — is thinking about ditching gas and going electric, Denver has a heat pump rebate available for them.”