Looking for some advice, looking at a prebuilt new home, and found something weird with the electrical. Safety wise I guess this seems fine, but it just doesn't feel right.

The main electrical panel in this house is rated for 100 amps, but the meter outside along with all the wiring on the utility side are rated for 200 amps.

Is this against electrical code in any way or was the builder just cheep? Saved a few bucks on wiring between the meter and panel, and on a slightly smaller panel.

Seems like it would be really simple to upgrade later with a new panel and larger wires on the home side to the meter? Just seems like something I don't want to deal with on a new home. Any way to convince the builder to upgrade the panel?

This is in Canada...

Adding on: It seems this is a relatively standard practice that no one in my social circle here was aware of. Still a little odd, given how little the cost difference is at time of construction, but not a real issue.

We're going to confirm with the builder they intended a 100 Amp panel in the plans, and might look at getting it upgraded right away if we decide to move forward.

Also, just thought I would add in a link to the load calculator I was looking at for this. It is based on the Canadian electrical code. https://www.blackboxelectrical.com/pages/electrical-service-load-calculator-for-single-residences-canada


1 Answer 1


I can't imagine they stuck a 200 amp meter in the box

The meter itself has no role in determining service ampacity. The power company hates a) stocking 6 different varieties of a thing in warehouses and on trucks when 1 will suffice, and b) failing jobs because of supply issues. Thus if you order a 60A service you will get a 200A meter.

At least with a 200 amp service and gas heat there's a comfortable 50 - 75 amps available for EV's one day.

Wait, that's your concern?? Nobody needs a service upgrade to charge an electric car.

Modern 4th-gen* EV charging protocols, factor into their design, the ability to charge off any service. The "charger" as novices call it, is not a charger at all. Its job is to tell the car how much current it can safely take Right Now, and then it passes the 120/240V straight through. The car must obey, and it must respond immediately if that capacity signal changes. That is how all car "chargers" work already. Even though most of them never change the signal.

Of course you know, your large appliances only take power when they are actually operating - e.g. your water heater isn't 4500W at all times (otherwise your electric bill would be 3200 kWH/$500 a month for the water heater alone). Most of the time, and almost all the time at night, your house is drawing 2 or 3 amps tops - certainly less than 35 amps even if an A/C happens to cycle on. So that's 65A available for EV charging all night, the key is to know when.

You see the opportunity: it's a trivial matter for an EVSE ("charger") to attach clamp-on ammeters to your service wires, and adjust the EV charge rate as needed to prevent panel overload. In 2023 we typically recommend the Wallbox Pulsar Plus and a power monitor, the pair about $800 US before sales tax. The Wallbox doesn't require Internet (the link to the service panel is hard-wired).

  • The wiring to the meter also seems to be sized for a 200 amp service (everything on the utility side), it's just the wire through the wall, and panel that we're undersized to 100 amps. Apparently this is relatively standard practice, cost wise just seems really weird.
    – GrassMan
    Commented Oct 1, 2023 at 23:31
  • The main concern is actually based on the calculator edited into the original post we would expect to around 95 amps in the winter with a few things going on at the same time. (Laundry, Cooking, Heat, Cars Plugged in, ext...) It might not happen often, but its a reasonable scenario, and its a lot closer then I want to be to popping that main breaker and that assumes we don't add anything else in the future.
    – GrassMan
    Commented Oct 1, 2023 at 23:34
  • The EV thing would also be a big issue if we ever got one, let alone 2 of them potentially. A tesla on a level 1 charger is only picking up 4.8 ish KM per hour, if the car is only plugged in for 8 hours. (reasonable assuming day of work, and evening activity) Commuting to work, we would be putting on more than double that per vehicle when we can't work from home. So bar minimum we would be up to 65 or 70 amps for overnight vehicle charging. Running AC, laundry, cooking, or basically anything else and our cars wouldn't be charged enough to get to work and back. Yes its a future problem though.
    – GrassMan
    Commented Oct 1, 2023 at 23:44
  • @GrassMan 200A service entrance wire is about $5/foot in bulk quantity. Service entrance runs are generally pretty short (like 10 feet or less) so even if the smaller wire were free (which it obviously isn’t) the savings potential is limited and may not outweigh the cost of stocking multiple types for a mass-scale builder. They have different considerations than a DIY’er doing a one-off job.
    – nobody
    Commented Oct 1, 2023 at 23:51
  • @nobody We did walk around some of the other homes in the development, and talked to 2 of the other people on the street. It seemed like the other homes on the street all had 200 amp panels based on the wiring sizes running into homes and the talking to the neighbours. The service entrance is only 4-5 feet.
    – GrassMan
    Commented Oct 1, 2023 at 23:57

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