I'm getting an EV charger installed, as we're getting an electric vehicle, and I want to check whether it's appropriate to do this install with the service we have now, or if we'll need to upgrade the panel before doing the charger installation.

Details: the EV charger will be run through a NEMA 14/50 outlet (40 amp charger). The house has gas heat, no AC (temperate climate), electric stove and dryer, and LED lighting. The usual other stuff for the most part - two TVs, one desktop computer, a fridge, a separate freezer, a microwave, a toaster oven. The house was built in 1980 or thereabouts, in California.

Also - if it matters whether the outlet is run from the subpanel (as all of the house is) or directly off of the main panel at service, please say so - I don’t know which would be preferable, and both are possible (as they’re both in or adjacent to the attached garage).

Range is on 50A circuit, dryer on 30A circuit.

image of subpanel notes

image of subpanel

image of main panel

image of main panel notes

picture of meter

clearer picture of main panel notes

  • What service do you have? I see a 90A breaker under a sticker that says "Service Disconnect". If you have 90A service and you're adding a 40A charger to an electric stove and dryer, it's time to upgrade.
    – jay613
    Dec 1, 2021 at 19:54
  • That’s part of my question I guess … the main panel mentions 125A max, but the breaker itself is 90A. Does that mean there’s room for more on the main panel, or is that just saying the panel itself could do 125 but I might only have ability to run 90 due to power co?
    – Joe
    Dec 1, 2021 at 19:56
  • With a clearer picture of the meter and any labelling on it, some people here may be able to tell you the size of your service. Even if it's 125A, you still ought to upgrade. Just guessing, if your range draws 40, your dryer 25, your car 30 and everything else 20 .... that's already over the continuous capacity of your panel and way over the capacity of your main breaker and most likely of your service. Look at the rating plates on your range and dryer for actual ratings. Assume you have everything on full power, since that's a realistic scenario.
    – jay613
    Dec 1, 2021 at 20:08
  • Added clearer pics.
    – Joe
    Dec 1, 2021 at 20:15
  • Well, that's a 200A meter in a 125A panel with a 90A breaker and unknown service size. To determine your capacity requirements requires knowledge of your floor area and other things and I'm not qualified but I'm pretty certain with the EV it'll be over 125. Everything will need upgrading, best case you have a 200A service drop but that's wishful thinking, it's probably 90. You may get some answers here from people more knowledgeable than me, but it's safe to say you need to hire an electrician to review your situation.
    – jay613
    Dec 1, 2021 at 20:34

1 Answer 1


Update: novice EVers always go straight for 50A because of being given wrong info, but at seven times level 1 charge rate, it's bonkers overkill (esp. for a typical Bay Area commute). 240V/20A is enough, noting that EVs become extraordinarily efficient in slow traffic, and you don't have deep winters to sap battery capacity. And also, new EVSE's ("chargers", but not actually) are now available that can put clamp meters on your service wires, and automatically adjust EV charge rate to stay within service limits. That means whenever you aren't running all loads at once, your EV can charge at max possible speed. Many electric companies including AMP require you notify them of EV charging.

First, I would have a conversation with AMP about why in green blazes is your main breaker 90A instead of 125A. I see 2 possibilities: #1 90A breakers are cheaper than 125A breakers, especially in 1980. If the house's Load Calc was under 90A, and that sounds about right, maybe the builder found a way to pinch pennies.

Or #2 a provisioning/delivery problem - they may not have the transformer ampacity up on the pole or pad, or they didn't in 1980 and may now. Obviously every power company is having to "reinvent" a lot of infrastructure to accommodate emerging tech like rooftop solar and EVs.

Or #3 the builder pinched pennies on the main feeder, using #3 aluminum between meter-main and inside service panel. That is good for 75A natively, or 90A for a whole house's service (rule 310.15(B)(7)). But that's a really weird size to even find, so that would surprise me. (and there's nothing wrong with large aluminum feeder.)

All of this will require a Load Calculation be done on your home. I'm not good at those, but it involves taking water heater and dryer power ratings, factoring range through some wild math, 1500VA for each 20A kitchen, bathroom, laundry and garage circuit, and then "3 VA per square foot" is a catch-all for all the little stuff, so you don't have to list PCs and TVs. (They haven't up-factored that for our highly electric lives, but they also haven't down-factored that for LED lighting. Probably a wash.)

My gut sense is your Load Calc will come out at 60-90A not including the EVSE.

Modern breakers

The panel labeling on both meter-main and panel indicate they are safety-rated for Eaton BR and BRD type breakers. That gives a wide set of options for replacement breakers. BRD quadplex breakers work a little differently than the Crouse-Hinds.

Try to bump your ampacity.

After the discussion with AMP, you will know if 125A is a trivial upgrade, or if service drop (lateral? 1980 neighborhood may all be underground?) needs to be upgraded.

You also need to evaluate the main feeder wiring between the meter-main and the 12-space panel. For 125A, due to a favorable 83% derate from 310.15(B)(7), the wire needs to be rated 104A. That happens with #2 copper or #1/0 aluminum, and aluminum wire is totally fine at these large sizes. Heck, it will be attaching to lugs which are made of aluminum (for good reason).

Whatever you can do to bump it to 125A will definitely help.

If your service is irrevocably 90A due to infrastructure limitations that are still relevant, I'm not getting warm feelings about supporting an EV of any size. You might be down to 16A (3840 W) or 40% of the rate you were hoping for. But like you say, good enough for 50 miles/day. If the car supports level 3 fast charging, look around the side of the local Target.

Fix the hole problem in the panel

The Crouse-Hinds panel uses a unique style of "half-width" breaker. The 2-pole half-widths straddle two breaker spaces. Their 1-pole half-width breakers come in "left-handed" and "right-handed" versions, and I think you have two there in breakers 10 and 11.

The problem is, the stack of 2-pole breakers on the left has an empty half-width hole at the top and bottom of the stack. This is a path for dust, leaves and curious fingers to get into the panel. Those MUST be filled. They make blank cover plates, but you can also put Crouse-Hinds half-width breakers there. It appears you have a left and right in breakers 10 and 11! So, have an electrician familiar with Crouse-Hinds carefully relocate them to fill the empty holes above 1 and below 6. The bus clips are fragile, and "force-fitting a breaker into a place it's not designed for will certainly mangle it beyond safe use. Hence the need for a careful expert in handling these largely unobtanium breakers.

That will leave an empty hole in the full breaker space formerly occupied by 10-11. Fill the empty hole with any Eaton BR breaker - they are cheap, and you'll never find an approved Crouse-Hinds empty-space cover that hasn't perished from age.

You could also junk ALL the Crouse-Hinds breakers and replace the lot with Eaton BR and BRD. Make sure that breakers for range and dryer, and to any NEMA 14 sockets, have common trip - they make quadplex models with and without it.

Where to put a 2-pole breaker in that

If you followed my advice above to fill those holes, there's an open space above and below breaker 12. Move breaker 12 up one space, and you can use the 2 spaces below to accommodate a 2-pole breaker for the EVSE.

"That was easy"

There's one other choice that can sidestep the requirement to upgrade your Main Feeder. But it's ugly, and you'll need a variance from your AHJ (Authority Having Jurisdiction) to use it. Look closely at the meter-main diagram. Yes, it has one breaker in it, as you'd expect. However, there are actually 4 breaker spaces there, which allows it to be configured as an obsolete and now-illegal configuration called "Rule of Six" -- where the so-called "main breaker" is actually up to six breakers. Their example drawing shows a quadplex breakers and four half-width singles, as six throws - that's an extreme use.

It would be possible to put the EVSE breaker right next to the main breaker, causing your house to have 2 main breakers. That's why you'd need a waiver, since it's illegal to do that since Rule-of-Six was outlawed.

(the point of Rule-of-Six was that as services got to 100A and larger, 15-60A breakers were affordable and plentiful, but 100A breakers were rare and "over the moon" in cost. (see start of this answer). So builders wanted to build panels with up to 6 main breakers - one each feeding dryer, range, Water heater, A/C and a subpanel for everything else. Overloading was avoided by making sure the Load Calculation was correct. Problem is, people would add stuff and not re-do the Load Calculation, and overload their service. This was outlawed for <=200A services when <=200A breakers got cheaper.)

  • Note that there's a goofy limitation in their panel's series ratings -- if they have a system that can put greater than 10kAIC at the lugs of the subpanel, they need to use a Siemens QP (designated replacement for Murray MP) breaker instead of an Eaton BR (even though their panel is otherwise listed for Eaton BR in addition to Murray MP) Dec 2, 2021 at 3:10
  • Update (partial)... two electricians in, two diametrically opposite answers. Probably both wrong. Sigh. (One says "Sure, I'll do it" (put a breaker in the main panel); but won't agree to pull a permit, so I'm assuming that's a bad sign... the other says "probably impossible without digging up the sidewalk", without actually checking what the service is.). Will be having convo w/AMP soon to see if I can get the answer myself...
    – Joe
    Dec 9, 2021 at 19:01
  • ... and the answer is 200A service. Yay?
    – Joe
    Dec 9, 2021 at 19:09
  • 1
    Wait. AMP thinks your service is 200A? Wow, that builder was cheap, all right. It's time to look at the size of the service wiring between the meter-main and the panel and see why they breakered it at 90A. Dec 9, 2021 at 21:07

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