Upgrading from 100 to 200 amps: when you need it.

A lot of houses in Harford County, Baltimore County and Baltimore City still run on 100-amp service. For many of them that's fine. It stops being fine when the house is asked to do more than it was wired for. This guide explains how to tell which side of that line you're on, what a 100-amp to 200-amp service upgrade actually includes, and what drives the cost and the schedule.

What “100 amps” and “200 amps” mean

Your service size is the most current the utility connection, meter equipment and main breaker are built to deliver to the house at once. It's usually printed on the main breaker at the top of the panel. Doubling the service doesn't make anything use more electricity. It raises the ceiling on how much can run at the same time.

Signs 100 amps may not be enough

• You're planning a big new load: a Level 2 EV charger, a heat pump, electric range or dryer, a hot tub, or a generator hookup
• You're adding square footage, a finished basement or a detached shop
• The panel has no open spaces and circuits are already doubled up
• The main breaker trips, or lights dim noticeably when large appliances start
• The panel is an older brand your home inspector flagged, and it's due for replacement anyway

None of these on its own proves you need 200 amps. They're reasons to run the numbers.

The load calculation decides

The National Electrical Code sets out how to calculate a dwelling's service load in Article 220. An electrician adds up the house's general lighting and receptacle load, fixed appliances, heating and cooling, and any new equipment you're planning, applies the code's demand factors, and compares the result to the service you have.

That calculation can land three ways:

1. The existing service can carry it. You may only need a new circuit, or a new panel with more spaces on the same service.
2. It's close. Sometimes a smaller charger setting, or not running two big loads at once, keeps you inside the existing service. We'll tell you if that's realistic.
3. It doesn't fit. That's when a service upgrade is the right answer.

We'd rather tell you that you don't need an upgrade than sell you one you don't. The calculation is the reason either way.

What a 200-amp upgrade includes

A service upgrade is more than a bigger panel. Depending on the house, it can include:

• A new panel with a 200-amp main breaker, and every circuit moved over and labeled
• A new meter base and the service-entrance conductors between the meter and the panel
• Grounding and bonding brought up to the code in force
• A surge-protective device and an outdoor emergency disconnect, both required for dwelling service work under the 2020 and 2023 National Electrical Code
• Coordination with BGE, which owns the meter and the service to the house

Which code edition applies depends on where you live. Our guide to which electrical code applies in Maryland covers it.

What drives the cost

We don't publish a single price for a service upgrade, because two houses with the same panel can be very different jobs. The biggest factors:

• Whether the meter location and service entrance can stay where they are
• Overhead versus underground service, and how far the run is
• The condition of the existing wiring that lands in the panel
• How many circuits move, and whether any need repair to pass inspection
• Drywall, siding or masonry work around the panel and meter

We look first, then give you the price before any work starts. If you're hoping a federal tax credit will offset part of it, read is there still a tax credit for a panel upgrade first: the 25C credit ended with 2025.

What drives the timeline

The electrical work is usually the predictable part. The schedule depends on the permit, the inspection and the utility. Each jurisdiction has its own permit process, covered in our guide to electrical permits in Harford and Baltimore, and BGE has to disconnect and reconnect service for the swap. We line those up and tell you what to expect for your address before we start.

How the big loads fit in

EV chargers

A Level 2 charger is often the load that tips a 100-amp house over. See EV charger installation for how we size the circuit and check the panel first.

Generators

A standby generator connects through a transfer switch at the service. Planning both together avoids doing the service work twice. See generators and backup power.

Older homes

In older attached homes the panel and meter are often in tight spaces. Our rowhome service upgrade guide covers what's different there.

Wyatt Electric has done panel and service work across Harford County, Baltimore County and Baltimore City since 1986. We pull the permit, coordinate the utility side and stay with the job through inspection.