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We recently did a remodel and have 150 Amp Service. As part of our HERS, we needed to increase the Solar and add a car charger. The Solar Company's master electrician is saying we are maxed out and they cannot/will not add the car charger as required by code. They said the total load should be 80% max and we're close to 100% without the car charger.

Builder's electrician who wired the house said it's fine.

See attached load count and calculations done by solar electrician. Any suggestions would be helpful.enter image description here

ThreePhaseEel
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Jon
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  • Where in the world are you? Different electric code will apply. – FreeMan Feb 28 '24 at 19:11
  • you have only 150A for almost 4K sq ft ?? – amphibient Feb 28 '24 at 19:15
  • Please revise your title to ask a clear, specific question. See [ask] and take the [tour]. – isherwood Feb 28 '24 at 19:19
  • The wiring was fine for what you have. Why mess with possible insurance issues and voided warranties, let alone a house fire. 150 Amps for a 4000 sq ft home seems pretty low. In my area the rule of thumb is anything over 1800 sq ft. gets 200 amps. Go for the upgrade. – RMDman Feb 29 '24 at 00:21
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    The range line given makes no sense, unless it's an allowance for an electric igniter on a gas range, and even then, 1000VA is frankly shockingly high for running gas range/cooktop accessories. Can you revise your question with the actual nameplate wattage of the cooktop? – ThreePhaseEel Feb 29 '24 at 03:28
  • A bunch of things here don't make sense. 1,500W for a refrigerator seems very high. Why two dryers? 1,000W for an electric range seems very low. etc. Have you plugged all this into an NEC Load Calc. spreadsheet? – manassehkatz-Moving 2 Codidact Feb 29 '24 at 03:56
  • EV charging is actually 80% of your 12,000 = 9,600 - i.e., you charge at 40A on a 50A circuit. So you don't need to upsize (derate) it a second time. But 40A is likely double what you really need, so if in the end (not clear here) you can squeeze in 20A but not 40A or 50A then you do that and call it a day. OR you put in load shedding so that when your hot tub isn't running you have plenty of power for EV charging and it works automatically. – manassehkatz-Moving 2 Codidact Feb 29 '24 at 04:06
  • Thanks for all the comments thus far. Home is in Boulder Colorado. House was remodeled from 2800 to ~4200 q ft. There is an electric wall oven and a gas range/oven. There are two laundry rooms.

    My understanding now is that the service line into the house from the feeder box is only rated at 150amps. So Solar electrician is recommending a sub panel to split line to house from solar and car charger.

    – Jon Feb 29 '24 at 04:30
  • Sounds like when the house was remodeled from 2800 to 4200 and (very likely) lots of stuff added like 2nd laundry room that the heavy up to 200 or 225 (whatever is the local usual offering) should have been done at the time. Now you really need to do that. – manassehkatz-Moving 2 Codidact Feb 29 '24 at 04:54
  • I’m voting to close this question because questions about local code are off-topic. Here's what's on-topic and off-topic. – FreeMan Feb 29 '24 at 13:11

1 Answers1

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The Solar Company's master electrician is saying we are maxed out and they cannot/will not add the car charger as required by code.

Because he doesn't know what he's doing with EVs and should stick to solar.

There's a technology called EVEMS that makes it easy and cheap to add EV charging to any "maxed out" panel. Further, it plays extremely well with solar, allowing a mode I call "solar capture". Which makes it pretty unconscionable for a solar electrician to not know about it, IMO.

I would consider either a Wallbox Pulsar Plus with its power meter, or the Tesla [Universal] Wall Connector with its Neurio meter. Both these meters clamp onto your service wires and communicate with the EVSE ("wall charger") to tell the car to adjust charge to avoid service overload. If you boggle at how that's possible, read the above link. Now if you don't want data cables and love delivering stable WiFi to everywhere in the house and your appliances coordinating via "the cloud", Emporia makes a slightly cheaper solution in their Load Management bundle.

Solar capture is this: Your house's loads are very variable through the day. Most of the day, the house takes little, and almost 100% of your solar production is exported. Solar capture monitors this and tells the car to take exactly the current that you would otherwise be exporting. That way, the solar power goes into the car's battery instead of being sold back to the utility. Why would that matter? Because very few people are getting "net metering" deals anymore - you're being paid far less for the solar you're exporting by day than you pay for the power you charge your EV with at night. So solar capture is a win anytime it's possible.

Car charger 50 amp...... 12,000 VA

Existing amp load: 147.06 amp... with EV 169.56 amp

WRONG! So the EV only adds 22 amps even though he flat out says it's 50 amps? No. The guy completely botched the Load Calculation there. If you look at the common NEC 220.82 Load Calculation, most loads get a 40% fold-down, which you see the guy doing above. E.G. adding a 5000W water heater only adds 40% of that (2000W) to the Load Calculation. This guy incorrectly applied that fold-down to the EV load. EV loads are so extreme they do not get a fold-down at all, and are treated at 100% (actually 125%) -- meaning a "50A circuit" 9600W EV station should actually add 50 amps, not 22 amps to the Load Calc. But again, EVEMS makes this entirely moot, and EVEMS is such a smart play for you for 2 reasons that you'd be a fool not to do it. Now you just need an electrician who actually knows the topic.

A second extreme falsehood here is that EV charging requires 50A. No it doesn't! That's appropriate for overnight enroute charging e.g. at a hotel, but bonkers overkill for almost anyone's home charging. Technology Connections' video, linked in the above article, discusses this at length. But again, with EVEMS we don't need to care, since we are able to game around the house loads.

SMH wow, the solar guy doesn't know about EVEMS. Alrighty!

My understanding now is that the service line into the house from the feeder box is only rated at 150amps. So Solar electrician is recommending a sub panel to split line to house from solar and car charger.

Well, that is absolutely correct, and there's the guy's solar competence shining through all their EV ignorance. Not a subpanel exactly, but you insert a panel between the meter and the so-called "main panel with all your breakers". This breaks you out of the "120% of panel bus rating" limit you would otherwise have, if the solar fed the existing panel.

Harper - Reinstate Monica
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