First of all, yes, we’re going to talk with an electrician. But here’s the story: We live in a 6-unit condo building. Below the building, each unit has one parking space. The electrical panel for the building is in a utility room that’s near the parking spaces. Some of the units are rented out, some are owner-occupied.
New renters in one of the units in our building have an EV. The owner is willing to install power to their parking space and the renters would pay for the charging unit. The owner got a quote from an electrician to provide and install new 50-amp sub-panel, provide and install 50-amp line for sub-panel, provide and install 50-amp GFCI breaker for sub-panel, run a 50-amp line from the electrical room to the parking space, and install a charger provided by the renters.
Will this have any negative effect on any other units, either now or in the future? Apparently the total power coming into the building is not changing? Does this reduce the power available to the other units? If, in the future, other units want to install EV charging, would the configuration installed for the current renter forestall any other possible configurations for the other units?
What ideally should be done? A quick fix for the one unit, or something that can be scaled in the future if other units also want EV charging? (Keeping in mind that the other units don’t want to pay for something they’re not going to use.)
You need to do a load calculation. The power company will size the transformer feeding your meter room appropriately. If the load for every unit goes by by 30A, the transformer needs to handle an extra 180A,
When we were in our condo our EVSE was somehow connected to our own breaker box. I have no idea the specifics but it was new construction.
Meanwhile future proofing for additional residents with EVs as time goes on - maybe the idea is a sub box that can handle several EVs with “load-managed EV charging infrastructure”?
Increased potential resale value of all units to know that the spaces are EV capable.
IMHO this is less a technical problem and more a collaboration/political one. You can spend weeks and months discussing what to do with the other condo owners (is there an HOA that can facilitate this?) to come up with some sort of scaleable, futureproof solution… or you can get this installed and ready by next week.
I think the chances of getting past this stage:
Are slim to none. Cross that bridge if and when you get there. It’s pretty unlikely the other units will all suddenly want EVs in the short term. And longer term, who knows what’s going to happen? Maybe smart load-sharing chargers will be more standardized, maybe public EV infrastructure will get better, maybe electricity prices will skyrocket from AI demand and EVs will be even less popular… not something to worry about today, IMHO. Until then, it’s first-come-first-serve for the unit that actually has an immediate need and are willing to pay for it. It’s not their responsibility to plan (and preemptively pay) for every possible future contingency.
Missing from this discussion is the electricity cost. Does each tenant have their own meter, or is it shared? Would the feed then come off the one tenant’s meter? Would it be simpler to put a NEMA 14-50 socket and put a plug on the charger unit, for future flexibility…? Otherwise, the occupant wishing to take the charger with them later, leaves a dead end circuit.
(I should note too the newer Tesla chargers have the capability to share one 50A circuit between two chargers, connected by a communications line so they ensure the circuit never exceeds the rated capacity - so there would be room for expansion, but again it’s back to how the power is metered…)
Also, I tell my Tesla to start charging at 12:30AM when most household loads are minimal, to avoid tripping the main household breaker. And, I’ve dumbed charging down by telling the Tesla to only charge at 26A instead of 40A (80% of 50A circuit) at home. Proper scheduling can reduce the risk of overloading your condo’s power, if/when everyone charges their EV and are considerate about it. I presume in future there will be distributed multi-point charging systems that will do this sort of job automatically (and likely track power for billing, instead of having to wire 6 different circuits). But for now, no such thing.
They exist now. Search for “dynamic load management infrastructure” - example:
Key is that they can be set to in aggregate only pull so much at a time and the software divvies it up intelligently. As one draws less the others can draw more. If I understand right in this case it is just sizing the one circuit to as large as the building feels it has capacity for, having a smart meter, its “energy gateway”, a router, and then each added charger has to be of the same type to network.
Thanks to everyone for your responses. And the remark from Reply about first-come first-serve / immediate need is spot on. So it sounds like we’d want to just let that one unit do their thing and not worry about setting up for the future for everyone else.
So now my main concern (and yes we will check with an electrician) is: Does their proposed 50-watt sub-panel branch off of their unit’s circuit, or is it a new independent circuit that will have an effect on the building as a whole, maybe reduding the available capacity for the other units? Their estimate said: (1) Provide and install new 50 amp sub panel. (2) Provide and install 50 amp line for sub panel. (3) Provide and install new 50 amp GFCI Breaker for car charger. (etc…) Does that sound like it comes off their own circuit or does it affect the building in any way? i.e. is a “sub-panel” a child of the unit’s, or a child of the building?
It sounds like the electrician didn’t specify. Running a new panel shouldn’t affect the power available to the other panels, if it’s set up properly.
It’s slightly more future-proof if it’s a separate panel, because then it could later be upgraded to something like ChargePoint, which would let each person using it pay for their own charge. But it’s probably not a big deal either way.
Does each unit have their own electrical service (separate meter provided by the electric utility and separate billing) and main panel? If so make sure that their electrician connects the subpanel to the correct main panel and you should be set. If the service is shared then that’s a different story.
For now, I would imagine the owner sets up his own service, sub-panel, etc. off his main panel. If he exceeds the max load for his unit, he will pop his unit’s main breaker.
The follow-on question I would have is - does the feed for the entire building add up to the total for the individual units? I.e. if the unit has a 100-amp panel, for now, the 50-amp comes off the unit’s 100A and the owner cannot exceed 100A total, charging or not. (The car would pull a 40A load, the code sying max 80% of breaker) For example, my house has a 50A circuit for the charger off a 100A main panel, and only once did I pop the main breaker (which is why I dialled charging back to 26A from 40A)
But you have 6 units? Is the total feed for the building rated as 600A, or is it built with the assumption that all 6 units will never be pulling 100A at the same time? (For example, add up all the breakers in my house, they total well over 100A. But I don’t plug a toaster in every outlet, so it’s a safe bet…)
The problem you - or future owners - will eventually run into is - do you want to have all 6 units do the same thing? Is there even room on the electrical room wall for 6 of the 50A sub-panels? How tidy will it look? And maybe while the first panel is going in consider this - my experience with electricians and telephone workers where I worked was - given a big open blank space, they will plunk a new panel or baord right in the middle, no regard for future needs and other equipment.
OTOH - if you get to the point where 3 or 4 others want chargers and want to install a load-balancing system with metering and charge-backs (as linked above), the first one or two who paid to install their own will balk at having to pay again their share of a group charger… I hear condo boards can be fun…
Each of the units has an electric meter that says CL200 which I think means each unit has 200 amps. So presumably the “new 50 amp sub panel” is associated with the meter for one particular unit. So each unit has 200 amps available, and that the EV charger would not affect anyone else’s electrical supply. (Correct me if I’m wrong.)
CL200 means the meter can handle up to 200A, it does not mean the service is 200A. CL200 meters are used for any service size 200A or less (60A, 100A, 125A, 150A).
My neighborhood is rather old. Many houses, built in the 1950’s have 60A fuses. When I sold mine, the insurance company made the buyer change to a 60A breaker.
