Electrical Grid Infrastructure

A household-scale “nanogrid” with direct current (DC) wiring could trim electricity use by almost a tenth compared to a conventional alternating current (AC) household system, according to a new analysis. The study combines computer simulation, laboratory testing, and rare real-life field data to provide some initial clues about the best opportunities to use DC power in a decarbonized energy system.

The power grid that connects homes and businesses to electricity is built on AC wiring, the result of infrastructure decisions made about a century ago. But most household electrical items, from lighting to computers to kitchen appliances, run on DC.

“This setup requires many conversions between DC and AC, all of which lose some energy,” says study team member Kevin Kircher, a mechanical engineer at Purdue University in Indiana. They also require additional devices such as inverters and rectifiers with the attendant use of critical materials like copper and aluminum.

As the push to “electrify everything” proceeds, those inefficiencies add up, prompting a growing number of researchers to analyze the potential of a streamlined all-DC setup. “We investigated the alternative of connecting natively DC devices through DC wiring,” Kircher says.

One of the most important such devices is a heat pump, a heating and cooling system that represents a big chunk of energy use in all-electric households. “I was surprised by how hard it was to find an off-the-shelf heat pump that could run on DC right out of the box. It was impossible, actually!” Kircher says. “While many heat pumps use DC under the hood, manufacturers configure them to plug into conventional AC outlets.”

So the researchers retrofitted a commercially available household heat pump, which they tested under controlled laboratory conditions. They also installed a retrofitted heat pump in an all-DC “test house” inhabited by a trio of Purdue graduate students. The researchers say it is the first laboratory test of the heating function of a DC-based household heat pump, and the first field test of such a device.

Both laboratory and field test data show that a conventional off-the-shelf heat pump can be retrofit to run on DC without loss of performance. The researchers then fed their laboratory and field test data into a model of a DC-based household nanogrid consisting of a rooftop solar array, a storage battery, and a heat pump. With a retrofitted DC heat pump, the system would use 8% less energy over the course of a year compared the same setup with an off-the-shelf, AC-configured heat pump. A heat pump designed to run on DC wiring would yield 9.2% annual energy savings.

These savings correspond to 12.5% and 16.7% lower annual energy costs, respectively, according to the model.

“With a relatively simple retrofit, homeowners with solar power could better utilize their system’s generated power,” and save on their electric bill—just by switching their heat pump to DC, says study team member and Purdue graduate student Aaron Farha.

In monetary terms, however, the savings work out to only about $60 per year. At those rates, it probably wouldn’t make financial sense for people to retrofit individual homes or heat pumps to run on DC power. Nor are we likely to be uprooting the whole AC-based distribution grid anytime soon.

“The important part is that in some ways these systems can live in tandem to each other over the long term,” Farha says. “AC power lines are still an efficient way to transmit power over long distances, and DC power works best when paired with on-site photovoltaics and electric batteries.”

And the energy savings identified in the study could be persuasive for installing DC in new construction or pursuing retrofits of bigger buildings. “There’s a global community working on DC technologies at various scales,” Kircher says. “In my mind the most important direction for work right now is to identify applications where DC makes economic sense.”

https://www.anthropocenemagazine.org/2026/07/the-overlooked-wiring-problem-in-the-clean-energy-transition/