400Amp Service


A post in another thread got me thinking and I didn’t want to derail that conversation.

For those people on the forums that have 400 Amps of service (either in one panel, or parallel feeds), how much power do you actually think you are using? I’ve seen a few times on here people mentioning x number of 20Amp breakers that total to over 200Amp, but really, when you take into consideration that its 200Amps per phase, I don’t think most people get that close.

I recently worked on a new 4500 square foot house. They installed a 200Amp service. I asked why so low and the response from the electrician was that with the exception of full electric heated houses, there isn’t really a need for it. Granted, this was new install, so appliances etc were pretty efficient, but it got me thinking.


I agree with you… Here in CA, a new house is 2x6 construction with exterior foam and R38 ceilings… That along with more efficient appliances, and LED requirements, I can’t see why a new home would need anything more than 200amp…

Now if you had a Tesla supercharger in your home, yes, you could be over 200amp… But as an energy consultant here, I make energy reports and hvac/mechanical layouts everyday… Given the level at which we build currently, a single a/c unit in a new home is usually 30~40amps…

Now, as you example electrian said, unless the home is full custom and all electric, 200amp is just fine…

Now I have seen people in this forum with multiple EVs and “special” setups in older homes, yes, I can see where they have a need for multiple panels and up to 400+amp service…


I’ll give another CA perspective. I live in a newish subdivision in the Bay Area built out in 1998-1999 with the type of construction @HiTechRedNeck describes, although the LED lighting was a primarily a retrofit - mostly can halogen lighting originally. All 179 of the standalone homes in the neighborhood, all between 3000 and 4000 sq ft., were built with 400A service, even though all used gas for forced air heating and hot water.

Why ? Likely due more to the the number of circuits in the homes - mine currently has 66 circuits after a few wiring additions over the years (EVs, outdoor lighting and heaters). They were going to need to install two panels anyway, so why not plumb for 400A.

As to actually usage - I never go above 200A, even with two Teslas and a Ford EV all charging at the same time with the AC on. I probably could in some ridiculous worst case scenario (Dryer on, AC on, cars charging, backyard heaters on, etc., backyard halogen lights on).


I think the sense hardware is not the longterm play. Already PG&E (and I assume others) offer data connections via smart meters. If you had this integration, you wouldn’t need the sense hardware. The value is in the data mining and the integrations with other platforms. My guess is that, 5 years from now, Sense is a software only company


re: longterm play, I also have a feeling that the IP that Sense is generating will have more value than the product platform. Fortunately, as it currently stands, the platform has good protections for its users’ data in the privacy policy, so I don’t think there’s tremendous value in data mining. Also, keep in mind that the current generation of smartmeters doesn’t have the capability to sample usage at high enough rates to use Sense’s ML tech, nor do the data backhaul networks have the capability to get that volume of information back to a useful location. But that could change.

re: 400A service, I have a feeling that it’s usually about breaker count, as @kevin1 notes. That said, it’s not too hard to crack 200A of usage with backup heat strips in a 3000+ sf house, or an electric tankless water heater, or a few EVs, etc.


@bhstark, I have a PG&E smartmeter today as well as a Rainforest Eagle to read it real-time, but quite honestly, it’s nowhere near a match for Sense for 3 reasons.

  • No integration with solar - could be done, but not today.
  • As @pswired mentioned, super slow data acquisition rate and delivery rate. Once per 2 seconds at best.
  • No identification of devices or integrations with home automations.

I do agree that eventually Sense’s biggest asset will be their software and machine learning IP.


I would assume that’s not some fundamental limitation on the A/D converters but more likely product decision “who needs sub-S sampling on power when you only care about kWh.” Just a guess
When I said “data mining” I was referring to the data set training ML models. There’s a threshold of accuracy where this tech goes from nice-to-have to a must-have. Its not there yet; my guess is the ML can only get you so far and the integrations are likely going to have longer term value


I think the PG&E limitation is the data backhaul network - they use a low power, high range mesh network. I think PG&E used Landis and Gyr’s Gridstream but not 100% sure. I don’t know max data rates, but it likely in the thousands of bits per second. Plus these meshes also have latency, typically only uploading your data every hour or so. Why send more samples than your network can handle.

But revenue grade meters do sample much faster locally for the power calculation, so they are accurate, usually thousands of times per second. Then the results are aggregated into the one or two second update readings.

From my perspective, the integrations with smart plugs are a double winner.

  • Value today for handling devices that might stump early machine learning
  • While collecting the “ground truth” to learn these devices in the future.


I would think you could talk to them about supplying a splitter/adaptor. Even with 400 amps service your still using the exact same two legs of split phase service but you have two legs of each of the 120. I just don’t know if it would be capable of identifying and combii g the sources