Should You Run Separate Electric for Your Massachusetts ADU?

By Buz Artiano, BuildX | February 2026

The subject of shared utilities comes up quite often with people planning to build an ADU. They want to know whether they should run a separate service line or share utilities with the main house. Which sounds like no big deal, but whatever you decide will affect everything from your monthly bills to your long-term options.

After building dozens of ADUs all over Massachusetts, we have seen what happens when homeowners make this choice without fully understanding it. At BuildX, we walk through this decision on every project we take on. But if you want the short answer, a dedicated service is almost always the best option.

Why Is a Dedicated Service the Right Choice for Most ADUs?

We always recommend that you separate as many utilities as possible, and the electric is number one on the list. Most people have 200-amp service in their house, but that's not enough power to run an ADU. On average, these units require about 125 to 130 amps of power just for themselves.

We recommend a dedicated 200-amp service. It costs almost the same as a 150-amp service, and with 200 amps for your ADU, you are guaranteed to never run out of power. Having that extra amperage matters, especially because energy codes now require us to account for electric vehicle charging.

What About the EV Charger Requirement?

Under the current energy code (see Massachusetts ADU guidelines), we are required to install a 60-amp outlet on the outside of every ADU we build for a future electric car charger. It is a fairly new law and it's not optional. Since we have to prove the system can handle that extra 60-amp load, 100-amp service would not be enough. The math just doesn't work.

The EV charger is the main reason that 200-amp service has become the standard for all ADUs we build. It accounts for the EV-ready requirement with plenty of extra for all of the other electrical needs the ADU has.

How Much Does a Dedicated Service Cost?

The cost really depends on your property. If you have overhead service with a utility pole nearby, adding a new line is usually pretty simple. If your electricity comes underground from far down the street, the trenching adds a lot to the cost. In our experience, the difference between 150-amp and 200-amp service is too small to even consider. You want to go with 200 amps and pay the small amount they charge to upgrade.

What If Your Electric Comes Underground?

We understand why this is such a common question, especially for homeowners whose existing service runs underground from the street. The good news is that you don't necessarily need to dig up your entire yard.

In most cases, we can run a new 200-amp service to your existing house location first, then run it underground from there to the ADU. The underground wire is not super invasive. It only needs to be 18 inches deep. But we also run a one-inch conduit right next to it in the trench for your ADUs internet cable, so everything is neatly buried together.

Another option, depending on your property, is if the main house is ready for a service upgrade anyway, we can install a 400-amp dual meter setup. That gives you 200 amps for the house and 200 amps for the ADU, all from one pole, but with two meters. Each unit will always be metered separately.

What About Overhead Service?

If you have overhead service with a utility pole nearby, running a new line is usually the easiest. We can add another overhead wire for the ADU and then run it underground from your house to the unit. We handle all the coordination with National Grid, including setting up the new account. You don't even need to speak to the utility company.

Will My ADU Get Its Own Address?

Yes. When you install a separate meter, the ADU gets its own address. If your main house is 58 Main Street, the ADU will become something like 58A Main Street. The main house keeps the original address, and the ADU has its own meter associated with the new address.

When Might Shared Electric Make Sense?

We almost always recommend a dedicated service line for your ADU, but that's not the case 100% of the time. The truth is, there are situations where sharing can work.

If your existing service comes from far down the street and runs underground, running a new line might mean digging up a huge part of your yard. If that's the case, sharing electricity is an ok compromise. You just install a private sub meter. A sub-meter is inexpensive and lets you track exactly how much electricity the ADU uses, even though it shares service with the main house.

The problem with that is if you share, you will likely need to make sure your appliance usage is mostly gas to keep the electric pull to a minimum. That means a gas dryer, gas stove, and gas water heater in the ADU to keep that electrical load down. With all gas appliances, the ADU might only need 20 to 30 amps, which a shared 200-amp service can handle.

But this limits your options and what you can do in the future. No situation is perfect, there are always tradeoffs, but we help you weigh them based on your specific property so you can make the right decision.

Why Does Separate Metering Matter for Rentals?

If you plan to rent your ADU at any point, even years from now, having separate meters means separate utility bills. The tenant just pays their bill directly to the utility company. You are not in the middle trying to calculate their share of your bill or dealing with disputes about usage.

This separation is one of the main reasons we always encourage homeowners to run separate utilities to their ADUs. That means separate septic, separate water, and separate electric. When it's time to rent the place out, you are already set up. Our site assessments include a full review of your current utility setup and the best path forward.

What About Future Condo Conversion?

Massachusetts law now allows ADUs to be converted to condominiums under certain conditions. If you ever want to go that route, separate utilities make the ownership transfer so much easier.

Shared utilities can cause problems in condo arrangements. For example: Who pays when the septic needs replacing? How do you split the bill fairly? With independent utilities from the start, each unit has its own systems. It is much cleaner if you decide to turn your ADU into a condo down the road.

Are BuildX ADUs Solar-Ready?

Yes. Every ADU we build is already set up for solar, whether you want to install panels now or later. The rafters are rated for the extra weight of the solar panels, we pre-run conduit from the crawl space to the roof, and we pre-wire everything as well. Also, if you ever get an electric car, you can just put the charger on the side of the building.

We don't believe you should have to take a saw to your brand-new house to install solar panels. The conduit costs about $200 during construction. If you decide to skip that and add it all when you do solar later, you are looking at $5,000 or more to install the conduit, plus the mess and aggravation.

Ready to Plan Your ADU Electrical Setup?

For most Massachusetts homeowners building an ADU, a dedicated 200-amp service is the right choice. This way you know you have enough power, it keeps billing clean for rentals, and positions you well for converting to a condo later.

If you want to understand how electrical service would work on your specific property, our site assessments include a full review of your current service, utility access points, and our recommendation for the best way to run the electric to your new ADU.