After living in their West Denver home for nine years, April Armijo and her five children were able to enjoy the luxury of central air conditioning for the first time in the last two weeks.

“Especially when we were cooking dinner, it was really hot in the kitchen,” said Armijo from her porch. “Now it’s nice. Nice and cool.”

Armijo lives in Dispersed West Public Housing, a 17-unit complex owned and operated by the Denver Housing Authority. Until recently, residents relied on small window air conditioners that Armijo said weren’t powerful enough to cool her upstairs bedroom during the city’s increasingly hot summers. To escape the heat, she often slept downstairs.

However, these homes represent Denver’s first attempt to fully electrify a public apartment complex, which brought with it the added benefit of central air conditioning.

On Thursday, local officials and affordable energy advocates gathered on the front lawn of the building to announce the completion of the $661,000 project, which was largely funded by Xcel Energy and Denver’s Office of Climate Action, Sustainability and Resilience. The climate office is funded by a sales tax approved by Denver voters in 2020.

Joshua Crawley, COO of the Denver Housing Authority, said his organization has built all-electric homes in the past, but this project is the first time it has retrofitted existing homes and removed all natural gas appliances. Even the gas meters behind each unit have been covered and will be removed.

“We are pleased to be able to eliminate the use of natural gas at this site and even more so to equip these homes with central air conditioning for the first time,” said Crawley.

Climate activists are advocating projects like these to ban natural gas from existing buildings. In addition to eliminating indoor air pollution sources like gas stoves, electrification also allows buildings to take full advantage of a grid increasingly powered by carbon-free power sources like wind and solar.

What has held back these efforts so far are concerns about reliability and affordability. A study published earlier this year by the National Renewable Energy Laboratory found that most households would see a reduction in their energy bills by using heat pumps, especially if they rely on energy sources such as fuel oil or comparatively inefficient electric resistance heaters.

Things get more complicated when a household relies on natural gas. The authors found that most high-quality, efficient heat pumps would help families reduce their energy costs, but these devices typically come with a higher initial cost.

Xcel Energy, Colorado’s largest utility, has also expressed concerns about whether the grid can handle a rapid transition to heat pumps. If more homes rely on electricity to keep warm, that could lead to a sharp increase in electricity demand on cold days.

To mitigate these spikes, the utility has suggested that many homes could use gas furnaces as a replacement for all-electric heat pumps. Climate activists and heat pump engineers, meanwhile, claim that the technology can effectively keep residents warm in Colorado’s climate without causing power grids to collapse.

At the press conference, Grace Lopez Ramirez, a senior area manager at Xcel Energy, said one goal of the new project is to study how fully electrifying the residential complex will impact the grid and energy prices.

“We’ll see. We hope that this project will provide the necessary insights into how customers can work together to reduce their greenhouse gas emissions,” said Lopez Ramirez.