How Much Does It Cost to Run an All-Electric ADU? (One Family's Real Electric Bills)

By Buz Artiano, BuildX | March 2026

Watch: The Real Cost of an All-Electric ADU (One Year of Bills)

If you are thinking about building an all-electric ADU, the number one question in your mind is probably what will the electric bill actually be? You've probably heard that heat pumps are efficient and that going all-electric is the future, but you live in New England and our winters here are brutal. We all know that electricity is not cheap, and nobody seems to be able to give you real numbers from a Massachusetts ADU electric bill that show you what it actually costs to heat, cool, and power one of these units every month.

My name is Buz Artiano, and we've built dozens of ADUs across Massachusetts at BuildX, mostly around the South Shore and Plymouth County. Every ADU we build is all-electric, which means we know all about heat pump sizing, electrical panel upgrades, and energy performance on every project. We handle everything, the design, the permitting, and the construction under one roof. And since we work every day with Massachusetts' very specific septic constraints, lot coverage limits, and the by-right ADU laws, we know exactly how these units perform in real life.

Pam and John Myette are BuildX clients. We built their 900-square-foot, two-bedroom, all-electric detached ADU in Plymouth for their son William. Their ADU was the first one ever built in Plymouth, and they've now lived with it for over a year through every season. They tracked their electric bills from summer air conditioning through winter heating, and they are going to show us those numbers.

Of course we are always excited to share data from families who had a great experience. We're telling the Myettes' story because they have a full year of real utility bills from a real Massachusetts ADU. We want to show you the actual numbers, which is much more useful to you than printing an estimate on a brochure.

How Much Does an All-Electric ADU Actually Cost Per Month?

The Myettes' all-electric ADU in Plymouth runs between $212 and $300 per month. That covers heating, cooling, hot water, cooking, and all general electrical use for a 900-square-foot unit. It gets up closer to $300 during the summer when air conditioning runs constantly. The lower bills are usually for spring and fall months and winter periods when those fuel assistance discounts apply.

Before they got their first bill, Pam and John thought it was going to be much higher than it was. Pam told us that they assumed the bill would be outrageous. When the first monthly statement came in at $300 they were so relieved. Their bill settled into the $212 range and they had no more worries about the operating costs of their brand new ADU.

Those numbers are from an ADU that uses all electricity. There's no gas line, no oil tank, and no propane. The ADU uses a heat pump system for heating and cooling, an electric water heater, and an electric range. Every appliance and every bit of heat is metered.

Watch: Plymouth's First ADU | Our Life-Changing Journey with BuildX

What Drives the Electric Bill in an All-Electric ADU?

There are three things that determine the monthly bill in an all-electric ADU. The main one is the efficiency of the heat pump system. Second is the insulation and air-sealing quality of the building. And the third thing is the electricity rate you pay to the utility company.

The heat pump uses the most power out of anything. A heat pump is a system that transfers heat rather than creating it by burning fuel. When it's hot, it pulls heat out of the indoor air and sends it outside. In winter, it does exactly the opposite, it pulls heat from outdoor air and moves it inside. Because it moves heat instead of creating it, a heat pump gives you two to three times more heating energy per kilowatt-hour than an electric resistance heater. The efficiency of a heat pump is what makes all-electric the best option in New England.

The building envelope is just as important though. An ADU built with continuous insulation, sealed air barriers, and high-performance windows holds all your temperature controlled air inside the unit. When the building is nice and tightly sealed, the heat pump runs less, which means lower electricity bills. Every BuildX ADU is built to current Massachusetts energy code, which requires blower door testing and minimum insulation values that keep your heat pump from having to work so hard.

The third variable is the electricity rate itself, and that's actually where the Myettes saved the most money.

Can You Lower Your All-Electric ADU Bills with Utility Programs?

Yes. The Myettes reduced their monthly bill by signing up for two programs, and both are available to Plymouth-area homeowners.

The first program is a competitive electricity supply program through Constellation Energy. In Massachusetts, homeowners can pick who their electricity supplier is, with the delivery still going through their local utility company. The Myettes switched their supply to Constellation, because they have a lower per-kilowatt-hour rate than Eversource. John said it was very simple, just contact Eversource, ask about available supply options, and enroll in the one you want.

The second program is Eversource's fuel assistance discount, which applies from December through May. For people on a fixed income who qualify, it gives you a 25 to 30 percent discount on electricity rates during the winter. John said that qualifying for fuel assistance on top of the Constellation rate is what brought their bill way down. If a person is on a fixed income and has built an all-electric ADU, Eversource gives you a discount for the months when heating costs are highest.

Both programs are accessed through Eversource. John recommended that anyone in Plymouth contact Eversource directly to ask about the best available plan.