CORE’s board was able to fast-track the grant approval process so the project could commit to being an all-electric community.
“We went to the board [and said], ‘We have to decide in the next two weeks if they’re going to put a gas line into this neighborhood. What can we do?’” Treadway said.
CORE provided Habitat with a $100,000 grant for heat pumps and mini-splits, Treadway said. He noted that using heat pumps instead of natural gas allows the homes to run on electricity with a 100% solar photovoltaic offset.
“There are plenty of net-zero homes that have gas heat, but they have more PV than they need or they have some solar thermal to heat the hot water in their boiler,” he explained. “When you’re truly electric for hot water and space heating, it just makes it a little cleaner [and] that 8kW PV in all 27 of these units is truly offsetting their electrical usage.”
Bilby of Holy Cross pointed out that natural gas was supposed to be a transition fuel to move away from coal to renewable forms of energy.
“We’re so close to being there that we need to really think about transitioning the infrastructure in the same manner that we were willing to transfer our infrastructure to natural gas,” Bilby said. “Projects like Basalt Vista are leading the way where they didn’t even bring natural gas into the facility.”
Designing a net-zero neighborhood
All of the homes at Basalt Vista will be powered entirely by electricity. Of the nine homes in the first phase of construction, four will be fitted with equipment donated by Holy Cross Energy, including solar inverters, battery inverters and batteries, hot water tanks and electric vehicle chargers, according to Bilby.
One of the questions Holy Cross hopes to answer is “can we set up one house to be self-contained, but also pull electricity from the other three units out there? How long can we do that for?” Bilby said. “We’re also looking at the ability to microgrid all four houses for a resilience demonstration.”
Holy Cross and NREL want to study “demand flexibility” in the project. Demand flexibility allows energy producers to shift consumption to match peak supply. A 2018 report from the Rocky Mountain Institute, a nonprofit that works with businesses on market-based solutions to encourage efficiency and renewable energy, found that households that employ demand flexibility technologies can lower their utility bills by between 10% and 40%. RMI estimated the incremental cost of these technologies ranges from $5 per controlled device for electric water heaters to $50 per kWh of thermal electric storage capacity. The report estimated the incremental cost of electric vehicle charging stations to be $100 per vehicle.
“When you look at a net-zero energy building, you can put as much PV on the roof as you can to offset the amount of energy used, or you can create its own little system and its own little incubator,” Bilby explained. “The PV knows when to charge the battery and the battery knows when to discharge to heat the water, and they all work together to create this symbiotic relationship of all these controllable assets.”
He noted that homeowners are getting more interested in microgrids: localized energy grids that can disconnect from the main grid to provide power during outages.
“People want that self-assurance that the battery’s there for them when they need it,” Bilby said.
‘Won the lottery’
Holy Cross’s goal for its part of the project is to collect “a whole bunch of data” and perform a cost-benefit analysis on net-zero homes “to see what it takes to ramp this from four units to 100 units, from 100 units to 1,000 units,” Bilby said.
Ultimately, the project could give Holy Cross and other energy stakeholders insight on “what it might look like 20 years down the road on our grid when we have 10,000 PV inverters that are working harmoniously to create their own grid.”
CORE shares Holy Cross’s goal of studying data gathered from the community for a larger purpose.
“We want to know that our estimates are correct. We want to know that these homes are actually going to perform [with] net-zero energy, and that they’re going to be quiet and comfortable places to live,” Treadway said.
He continued, “NREL’s studying smart-grid connection of all of these homes. That’s a really exciting opportunity for CORE because then we’re not just pushing PV on your roof, we’re pushing a smart and a beneficial way to connect it to the grid so that utilities can benefit and your bill goes down or goes away.”
There are some lofty goals for the project in terms of the impact on building efficiency, but as Gilbert of Habitat pointed out, the greatest impact will be on the people who live there.
“When people see these homes, they’re going to be blown away. They are truly aspirational,” Gilbert said. “They’re not just a box. They have really nice post-and-beam pieces out in front and out back.”
He added, “We want the teachers to feel like they won the lottery.”