What does 200 A or 400 A mean?
The number is the rating of the electrical service: the utility connection, the meter and the main breaker. It is the most current the house is built to draw at one time. The Massachusetts Clean Energy Center suggests homes with less than 200 A consider upgrading for heat pumps, solar and EVs. Large homes may have 400 A or more.
What pushes a 200 A house toward 400 A?
Electrification. An EV charger, heat pumps that replace an oil or gas boiler, an induction range, a heat pump water heater, a pool heater or an addition each adds load. On a load calculation those add up fast, even though the car charges at night and the heat pumps work hardest on cold mornings.
| Question | Upgrade to 400 A | Manage loads on 200 A |
|---|---|---|
| What the load calculation counts | Every load at its demand value | The energy management system's setpoint for managed loads |
| Utility involvement | Work request, design, payment and a scheduled connection | The utility service stays as it is |
| Inspector | Inspects the new service | Inspects the energy management system |
| Daily life | Everything can run at once | Low-priority loads pause during peaks |
| Extras | Room for future loads | Circuit monitoring, outage scenes, battery and EV control |
What does the utility upgrade process look like?
In Eversource territory the electrician starts a work request for new or increased service and gets a work request number that tracks the job. After the town wiring inspector gives final approval, Eversource says it installs the service within 5 business days, provided its requirements are met. National Grid, Unitil and the municipal light plants have their own processes.
How does managing loads keep a house on 200 A?
Section 220.70 of the 2023 National Electrical Code lets the electrician use an energy management system's ampere setpoint in the service load calculation, with the system installed under 750.30. With Savant, modules sit on the circuits you choose. When the house nears its limit the system turns off the lowest-priority circuits, then turns them back on when use drops. Savant's service upgrade avoidance was approved in October 2026. Your electrician's load calculation decides whether it works for your house.
The step-by-step version is in how to avoid an electrical service upgrade, and the homeowner's view is in home load shedding explained.
What about 400 A to 600 A?
The code rule does not change with the service size, so a large house on 400 A can plan the same way. Bigger homes usually have more loads that can wait, such as snow melt, pool equipment and a second or third EV. Savant lists its Power Storage for services from 200 A up to 800 A if a battery is part of the plan.
