320 or 400 amp service: when to go past 200 amps

Most houses that feel cramped on 200 amps aren’t. They’re short on breaker spaces, or their load is poorly distributed. Both problems can be fixed without redoing the service.

But real cases do exist. This guide helps you tell them apart, because the price gap between “fixing it another way” and “going to 320 amps” runs into the thousands of dollars.

When 200 amps really isn’t enough

In our experience on the North Shore and in Laval, a 200 amp service is truly outgrown when several of these add up:

• A large electrically heated house, over 3,000 square feet, with several zones
• Two electric vehicles charging in the evening, with no load sharing
• A detached garage or workshop with heavy tools, a compressor or a welder
• An electrically heated pool, often with a spa
• An accessory dwelling unit or an addition with its own heating load
• A central heat pump with electric backup heat that piles on top of everything else in January

One of these on its own almost never justifies going past 200 amps. Three or four together, yes.

320 or 400: the difference

These two numbers actually describe the same equipment from two angles.

In a house, the standard setup past 200 amps is a meter base rated 400 amps, with a continuous capacity of 320 amps. That’s the usual safety margin: you don’t run a service at its full rating continuously. That’s why people commonly say “320 amps” for a home, and “400 amps” when they mean the equipment rating.

A true 400 amp continuous service does exist, but you’ll mostly see it in commercial, institutional and multi-unit buildings. On a house, it’s rare, and it needs an even stronger load calculation to back it up.

The possible setups

Going past 200 amps doesn’t mean installing a panel twice as big. In practice, three setups keep coming up.

Two 200 amp panels fed by a 400 amp meter base. It’s the most common setup in homes. Power arrives at a single meter base, then splits toward two service boxes, often one for the house and one for the garage, the workshop or the accessory unit.

A main panel and a remote subpanel. When the extra load is concentrated in one place (a detached garage, for example), we run a dedicated feeder to a subpanel instead of stretching many circuits over a long distance.

Keeping the 200 amps with load management. It’s the third option, and it’s the one we choose most often when the calculation allows it. It touches neither the service entrance nor the meter.

What the load calculation has to show

A load calculation isn’t an estimate or an electrician’s opinion. It’s a standard method, set out in the Code, that adds up the living area, the heating, the fixed appliances and the special loads.

Past 200 amps, it matters even more: it’s what justifies the capacity you ask for, to the inspector and to Hydro-Québec alike. Since 2026, it must also include the load of EV chargers.

It has to show three things:

• That the calculated load really exceeds what a 200 amp service can handle
• That this load can’t be brought back under the limit with load management
• That the capacity requested matches the need, with no needless oversizing

You should also know that Hydro-Québec has to confirm the capacity available on the grid at your address. In an older or already busy area, that isn’t automatic, and this check is part of the schedule.

What drives the cost up

The cost doesn’t follow the amperage in a straight line. It climbs in steps, because each threshold changes the nature of the job.

The whole service entrance. Mast, hardware, meter base, conductors: everything is larger and rated higher, so it costs more and is heavier to handle.

Two service boxes instead of one. Twice the equipment, plus the work of splitting the circuits between them.

Hydro-Québec’s schedule. This is the part few people see coming. The standard allows a master electrician to disconnect and reconnect the service themselves only up to 200 amps, at 120/240 V. Above that, Hydro-Québec has to step in, and the timeline is no longer in the contractor’s hands.

Distance and routing. A feeder to a detached garage crosses the yard: trenching, conduit, and putting the yard back in shape.

Grid capacity. If the area can’t supply it, there may be work on Hydro-Québec’s side, with delays and sometimes fees.

For reference: at STM-Électrique, a 200 amp service entrance and panel redone together on a single-family house come to around $2,900. A 320 amp service is well above that, because it’s a different job, and it’s priced after the visit and the load calculation, never over the phone.

Frequently asked questions