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How to convert your home into a small power plant, and make your money back doing it

The 1955 Cape-style home in Needham, which his family bought in 2000, was the “perfect candidate” for the transition, Mathew Tuttelman said.ryan huddle/Globe Staff; adobe

Mathew Tuttelman decided he was never going to pay a utility bill again — no gas, oil, or outside electricity to heat, cool, or power his 3,500-square-foot home. He was going to build a net-zero home, a structure that produces as much energy as it consumes.

Tuttelman, a senior account executive at CPower Energy where he provides energy expertise to companies, was motivated to cut his bills and his carbon footprint to combat climate change.

The 1955 Cape-style home in Needham, which his family bought in 2000, was the “perfect candidate” for the transition, he says. Between tax incentives from the state and Washington, D.C., here’s how he’s almost reached his goal.

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His first move was installing solar panels in 2019.

Solar panels (33 total)

Illustration of Solar panels on a roof

Upfront cost: $39,000

Savings: 30 percent, or $11,700, from federal incentives, plus an additional $1,000 state tax credit.

Final cost: $26,300

Payback: $4,500 annually

Estimated system payoff: 5.5 years

Source: Mathew Tuttelman, Energy Star, Mass. Department of Revenue

Next move: a home battery in his basement that stores energy to run his home in the event of a power outage. Last year, Tuttelman’s family lived through a 36-hour power outage, comfortably, thanks to the system.

Battery

Illustration of home battery in his basement that stores energy to run his home in the event of a power outage

Upfront cost: $23,000

Loan: Borrowed the money at zero percent interest on a seven-year loan

Estimated system payoff: 3.5 years

Source: Mathew Tuttelman

Then he insulated his home, creating a seal to keep heat from escaping.

Insulation

Illustration of rolled up home insulation

Upfront cost: $3,300

Savings: Mass Save picked up 75 percent.

Final cost: $740.

Source: Mathew Tuttelman, Mass Save

Last move, ditching the gas furnace and replacing it with two geothermal heat pumps, which use warmer temperatures underground, between 45 and 75 degrees Fahrenheit depending on the location, to transfer heat to the home in winter. Then in summer, when the ground below is cooler than the air, the system works in reverse.

Heat pumps (2)

Illustration of how a heat pump works

Upfront cost: $50,000

Savings: $15,000 from Mass Save, then a 30 percent tax credit from Washington DC, knocking off an additional $10,500

Final cost: $24,500

Estimated system payoff: Between 7-8 years

Source: US Inflation Reduction Act, Mass Save

Last year, a team from Dandelion Energy, a company that installs geothermal systems in the Northeast, drilled two 5-inch diameter boreholes, 350 feet deep, in Tuttelman’s yard. Then, the company connected the boreholes with lines that come into his house through the basement. Water and antifreeze solution coarse through pipes where the heat exchange occurs.

“It seemed like it was a no-brainer,” Tuttelman said. “A better technology that was going to use no fossil fuel, was going to be more efficient, and someone else was going to pick up more than half of the cost.”

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The total price tag for the entire home project was roughly $75,000, after rebates. But Tuttelman says it will pay for itself in about six years through energy cost savings.

Other benefits include the stress savings of not having to guess when a furnace, which typically lasts about 15 years, is on its last legs. The underground infrastructure for geothermal heat pumps can operate for 25 to 50 years, according to the US Department of Energy.

Mathew Tuttelman, with his dog Oliver, controls his home’s temperature through his smartphone and keeps monitors in his basement office to track the ebbs and flows of heat and power usage within his home.David L. Ryan/Globe Staff

His steps taken collectively, Tuttelman is close to his goal of living in a fully net-zero home. He still wants to install new windows to lower his energy needs and get rid of his hot water system that runs on gas. To do that, he needs to install a heat pump water heater.

John Sterman, a professor at MIT’s Sloan School of Management with a focus in sustainability, achieved the holy grail of net zero eight years ago. His 1920s Lexington home was due for an update, but instead of just “upgrading and renovating,” Sterman decided the “incremental cost of going deeper and doing a retrofit” was the right move.

A deep energy retrofit enhances a home’s sustainability and environmental footprint by using a “whole-systems approach.”

Sterman said he asked himself what actions would have the biggest payoff and went from there. For example, his home’s original windows from the 1920s were in rough shape, so he decided to tighten the building’s envelope, resulting in wider windowsills, where, added bonus, he can now display a robust plant collection.

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Window replacement

Illustration of energy efficient windows

Upfront cost: Highly variable by quality, size, and design.

Estimated savings: 7 to 15 percent on annual energy bills.

Federal tax credits: Up to $600 (or 30 percent of product cost) for upgrading windows in one taxable year.

State rebate: Mass Save offers $75 rebate per Energy Star window

Source: Energy Star, Mass Save

His remodeled home, which includes an air-source heat pump and solar panels, now produces roughly 40 percent more energy than it needs, all with zero fossil fuels. “My house is now a power plant,” he likes to say.

He estimates that without the retrofits, his annual gas and electricity bill would be about $3,200. Instead, he gets paid about $3,375 for his excess solar electricity production, in addition to charging two cars for free.

Heat pump water heater

Illustration of Heat Pump Water Heater

Average installation cost: $3,200 according to Mass Save

Estimated savings: Medium-sized households save $410 per year according to the Department of Energy.

Federal tax credits: 30 percent of project costs, up to $2,000

State rebate: Mass Save offers Up to $750 per unit

Source: Energy Star, Mass Save

Sterman acknowledges that he had the luxury to afford these investments, but says the economics have shifted dramatically since his installation — subsidies, tax credits, leases, and loans have made solar panels and heat pumps much more affordable. And while taking the plunge can be daunting, between the upfront cost and time investment, he says people should “consider the costs and benefits, not just the costs.”

At his home: no more cold spots in winter, ice dams, or risks of frozen pipes. With the radiators removed, he has more space. And with no fossil fuels used for cooking, his family has no exposure to pollutants that can cause respiratory problems.

“It’s a safer, more comfortable, quieter, and bigger place than it was before,” says Sterman. “All these benefits came as part of the deep energy retrofit.”

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Alexa Coultoff can be reached at alexa.coultoff@globe.com. Follow her @alexacoultoff.