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I have a 125a service that’s part of a multifamily setup. I have been told by a licensed electrician contractor that upgrading my service to 200a would likely require $10k+ due to also needing to upgrade components at the meter bank that feeds multiple units. Let’s take that for granted for this exercise, but happy to hear feedback on this as comments.

My 125a panel is almost full in breaker slots and load capacity, and won’t support adding circuits for a few backyard appliances (hot tub, sauna, cold plunge).

The electrician asked if I could disconnect the 50a EV charger, which I do not currently use, in order to free up breaker space and load capacity. While reasonable, I would rather keep that feature of the home in case I do end up wanting to use the charger in the future.

I am wondering if it’s possible to have an electric panel that can dynamically disconnect or prioritize circuits depending on real time demand. The idea being that the system will keep me from overloading the 125a service by switching off power to the EV circuit if the backyard appliances are on.

I am only interested in code compliant solutions. My jurisdiction uses the NEC 2020 code with these amendments.

What are my options?

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  • If you don't actually plan to charge an EV any time soon, don't go overboard trying to keep the EV circuit powered right now. Go ahead and disconnect it and just make sure you reserve breaker space to hook it back up (likely with a load shed device) later. Just don't rip out the wiring, as installing the wiring is usually the hard/expensive part.
    – nobody
    Sep 28, 2023 at 2:45

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There are EV systems that will reduce the available current the car is allowed to pull based on the load on the rest of the house.

They way they do that is by monitoring current probes on the feeders of the panel and then telling the EV it is allowed to only pull less amps.

That way you can entirely discount the EV charger from the load calculation.

I am wondering if it’s possible to have an electric panel that can dynamically disconnect or prioritize circuits depending on real time demand.

Yes those are called "smart" panels which are starting to arrive on the market. Those will disconnect low priority loads (like the tanked water heater when there is still some hot water) when higher priority loads are active (like cooking or your leisure backyard appliances). These are going to be compatible with a smart EV charger to give the leftovers to the car to charge with.

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  • @FreeMan Could you clarify what you mean by "the majority oft he cost will be already budgeted for"? The electrician I contacted for this work thinks that it will be quite expensive to upgrade my service due to the way the community is setup. Granted, I do not know market rate for these panels yet, and only have one bid. It's still early in my research. Sep 26, 2023 at 14:08
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    @FreeMan the entire point of the smart panel is to manage an overloaded panel when it doesn't have leeway to let everything run at once. If you could put in a service upgrade and run everything at the same time the smart panel is useless. Sep 26, 2023 at 14:15
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Part 1: EVs

The idea being that the system will keep me from overloading the 125a service by switching off power to the EV circuit if the backyard appliances are on.

I find it interesting that you're wanting to do that with the one load specifically designed to be able to do that. I mean, they put a lot of tech into EVs to enable you to do exactly that thing. Except better.

For the EV part of the equation, see this Q&A here.

Implementation wise, you need a $450 Wallbox Pulsar Plus from Costco, a cat5e "ethernet" cable, a $300 power monitor that goes inside the main panel, and that's it. The EV charging will automatically self-regulate so it doesn't overload your panel.

It will charge at full speed until A/C, water heater, pool and sauna all happen to cycle on at the same time, then it will reduce to 25 amps. If you then ALSO turn on a hair dryer, it will reduce to 12 amps. But it will not stop. And of course all those loads are unlikely to kick at midnight.

Emporia's unit can do the same trick but REQUIRES a $125 software upgrade and functioning 2.4 GHz WiFi at both panel and parking spot. No WiFi, it defaults to a very slow speed. Do not use an Emporia without the software upgrade, because without it, no WiFi = highest speed, which is not safe. It is not UL Listed as a result.

Before you go "oh noes, that's $750 and I already like my non-Wallbox EVSE", yes, you can get dumb load sheds that simply do a hard power cut to absolutely any EVSE (“charger”). They cost more than $750, because they're doing it the hard way - with a hard interrupt of 40A (arcing and degrading the contactor) and generally suck. If you are doing session based charging (e.g. authenticating with Bluetooth to serve as a anti-Karen Lock), any hard power cut will end your session and stop charging.

(Karen locks are to keep an over-entitled neighbor from plugging into what they have decided is a free public station. The Wallbox has a Bluetooth lock which does not require functioning WiFi. The Emporia has similar if the WiFi is up.)

Part 2: Everything else

My 125a panel is almost full in breaker slots and load capacity, and won’t support adding circuits for a few backyard appliances (hot tub, sauna, cold plunge)... I am wondering if it’s possible to have an electric panel that can dynamically disconnect or prioritize circuits depending on real time demand.

The SPAN panel will do that, but since you bristle at $10,000 for meter work, I'm guessing that's Right Out at about $8500 installed.

However, you can still get this functionality with "dumb" load shed devices such as SimpleSwitch, DryerBuddy and the like. These knock out one load when another one is pulling. Many of them are marketed for EV charging, but disregard that - as dumb switches they are inferior for EVs. But very fit for dumb appliances.

I covered that material in the above link. For a catalog of those, see Reddit's load management wiki. These are costly, but can effectively have one load pre-empt another (dryer pre-empt water heater, etc.)

However, you should note that two different devices both putting CT clamps on the service wires is not going to work. They will dynamically "fight each other", causing pulsing power on both. So don't use a Wallbox for an EV and also a DCC on a hot tub.

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You could put in a transition switch for EV charger and backyard appliances, so only one or the other can run at the same time. You will need a subpanel for the new loads, so put the transition switch there and run the EV charger feed from it.

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The electrician asked if I could disconnect the 50a EV charger, which I do not currently use, in order to free up breaker space and load capacity. While reasonable, I would rather keep that feature of the home in case I do end up wanting to use the charger in the future.
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I am wondering if it's possible to have an electric panel that can dynamically disconnect or prioritize circuits depending on real time demand.

You are either completely overthinking something or I am misunderstanding the problem.

If your main panel is physically out of space then get a subpanel installed.

If you are tripping the 125A breaker then you need a bigger service, period. 125A is barely enough for a single family let alone a multifamily home.

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  • The 125A service is for a single unit within a multi-family setup. The first electrician I contacted said that I can't "just add a subpanel" since it might not pass inspection due to safety. I'm assuming that they meant that some due diligence should be made to compute the new load calculation instead of relying on the circuit breaker tripping. Does any of that make sense to you? Oct 2, 2023 at 22:20
  • @fernandomrtnz You should contact more than one electrician. Who came up with the idea to "prioritize circuits depending on real time demand"? That sounds like a recipe for disaster and way more dangerous than a subpanel. "Due diligence" - LOL. Since this is a multi-family rental, code enforcement is probably much more strict since you're risking the lives of several other families, you're basically being treated like a business. My gut tells me the first guy is trying to fleece you.
    – MonkeyZeus
    Oct 3, 2023 at 15:08

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