Will Your Electric Service Need an Upgrade for an ADU?

By Buz Artiano, BuildX | February 2026

This is another fairly common question we get from homeowners when they are considering an ADU. They want to know if their existing electrical system can handle the additional pull from an ADU. And they are smart to wonder that, especially early on because the answer directly affects the project budget and timeline.

Trying to figure out all the specifics like amperages, panels, wiring, utility coordination, and more can be totally overwhelming. Most homeowners have never had to think about any of that sort of thing. At the end of the day, all you want to know is: will this be a simple connection to my existing power or is it going to be a major infrastructure upgrade? At BuildX, with our experience building ADUs across Massachusetts, we have seen it both ways. After walking countless properties and evaluating electrical systems firsthand, we can tell you that the answer depends on a few things, and we are always upfront with clients about what they are facing from the very first visit.

Why Do Most ADU Projects Require an Electrical Upgrade?

We kind of already touched on that. A modern ADU with electric heat, air conditioning, an electric stove, electric dryer, and the EV charger pulls a lot of power. Remember how we said that the average ADU pulls 120 to 130 amps with everything running? The EV charger requires 60 amps all by itself. Under the current code, there must be a dedicated 60-amp circuit for a future electric vehicle charger. That requirement alone forces us to bump it up to at least 200 amp service for the ADU.

As we tell our clients: we have to show we have a 60-amp dedicated box for a car charger. That is the fast charger you want if you get an electric vehicle. So when you add up the heat pump, the electric stove and dryer, and that 60-amp EV provision, you are quickly at or beyond 140 amps before accounting for lighting, outlets, and other loads.

What Size Service Does an ADU Need?

We always install 200-amp service for our ADUs. It makes no sense to go with 150-amp service because the cost difference is so little, and 200 amps just ensures you will never run out of power.

Some homeowners ask if 200 amps seems like overkill for a small space. It may seem that way, but when you account for the EV charger, a heat pump system, and appliances, 200 amps gives you the wiggle room you are going to need. We have had clients who initially wanted to minimize costs by installing 150 amp service, but they always decide on the 200-amp recommendation once they see the numbers.

What Are Your Options for Providing Power to the ADU?

There are several different ways we can go depending on your current electrical setup and property layout. We evaluate each property individually for the best solution, but these are the most common ways it can be done.

How Much Does an Electrical Service Upgrade Cost?

The cost varies quite a bit based on your property and existing infrastructure. A new separate 200-amp service for the ADU, like we talked about where it's run overhead and then underground, is typically included in your overall ADU project cost. It is a standard item on our estimates.

A full 400-amp service upgrade with trenching from the street and everything can run approximately $22,000+. That is because it involves digging up the yard, running new wires from the street, installing a new meter, and upgrading the main panel. If your electricity is currently underground and comes from a distant connection point, the trenching can add a lot to the cost. But the specific numbers depend on your property, and we provide exact figures during the planning phase after coming out and evaluating your site.

Does BuildX Handle Utility Coordination?

Yes. We coordinate everything with the utility company, as a homeowner you never even have to talk to them. When people ask if they need to contact National Grid or Eversource directly, the answer is no, we will handle everything. The permit applications, the service requests, the inspections, all of that coordination is part of our process. You don't need the headache of managing that yourself.

What About Solar Readiness?

Under the current code, we make every ADU solar ready as a standard. That means we install all the conduit from the roof area to the electrical panel so that adding solar panels later becomes much easier because the infrastructure is already in place.

Combined with the EV charger pre-wire, your ADU is positioned for future electrification without requiring another electrical upgrade down the road.

If you want to understand exactly what electrical work your property needs, we are happy to discuss that with you during our initial site visit.

Planning Your ADU Electrical Needs

Most ADU projects in Massachusetts require some kind of electrical upgrade. The upgrade that is best for the job depends on your existing service capacity, your property layout, and whether you want the ADU to be all-electric or part electric and part fuel powered. A separate 200-amp service with its own meter is the cleanest solution for most homeowners, especially those planning to rent the unit.

The electrical configuration affects your project budget, your ongoing utility costs, and your flexibility for future upgrades like solar or additional EV charging. Getting clarity on this early helps you make informed decisions about the rest of your ADU project.