I received a pricey estimate for a NEMA 14-50 installation because I apparently need an automatic transfer switch. Now I think I will go with a NEMA 14-30 DIY install instead. I am just wondering if my breaker will be able to handle the load without any issues. Also, the electrician said my home currently has an 88 amp load, and the addition of a 14-50 would raise that to about 112 amps. What would a 14-30 raise it to?

I plan on using this outlet mainly at night to charge my EV. I want to use 10 AWG Romex SIMpull NMD90 (10/3), routed from my breaker in the basement to my garage.

Edit: @Harper @machavity Sorry for the late response, the system wasn’t letting me for some reason. I don’t know how to do a load calculation myself (haven’t understood how to do it properly based on whaf I’ve searched online) so I’ve just mentioned what my electrician said. I have an Eaton breaker. Here are some pics: https://imgur.com/gallery/KYHLdjO

The major appliances that I can think of are: fridge, dryer, washer, air conditioner (only during summer), heater (fall/winter), furnace.

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    What is this about needing an ATS to install an EV charger?! What make and model of charger are you trying to install? Commented Jan 10, 2019 at 3:54
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  • I agree with the? on the ATS. If your actual load is 88 amps I am not sure how your electrician came up with 112a when adding a 50 amp outlet. We would need to know what the actual draw on the charger. Did the electrician measure the amperage to come up with 88 amps? If your true draw is 88 amps I don't know of any EV chargers that would work without upsizing the service.
    – Ed Beal
    Commented Jan 10, 2019 at 15:11
  • @machavity I don't think so, there's no way to get to 88 or 112 totaling up 15, 20 and 30 etc. It sounds like he did a loadcalc, using a rule that estimates needed service based on average usage. Obviously your 50A charger is dinging you for 24A more of general service need, which you are correct is a theoretical number and does not correspond to reality. Commented Jan 10, 2019 at 17:08
  • @Harper Did you mean to reply to Ed?
    – Machavity
    Commented Jan 10, 2019 at 17:16


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