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Question DetailsAsked on 4/12/2016

can I charge my electrical car with 100amp electrical panel in my garage ?

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1 Answer


Essentially all electric/hybrid vehicle plug-ins (excluding some golf-cart sized brands) require (in the US) a unique type J1772 power outlet, sometimes with individual power regulation and surge and overcurrent protection, so you will undoubtedly need an electrician to put that in anyway. Generally, a standard 15A outlet circuit is limited to 12A demand in continuous charging use (personally I would not go over 10A), so unless you use slow charge rate on a low-amperage Level 1 outlet car like A Volt you will almost certainly need a dedicated 220/240V circuit and outlet for your car. Almost all all-electric cars require a Level 2 220/240V dedicated circuit.

Whether your current panel has the power capacity needed depends on your car model (some draw only 8-20 amps at 120V while charging so can run off a normal outlet designed for winter block heaters (commonly 20-30A capacity) or at the low end even a normal utility outlet, but some draw up to about 20-25KW, which requires about a 100-120A circuit at 220/240V - so at or above the total capacity of your existing panel.

Generally, I would say if the 100A panel is the panel for the entire house (as opposed to an independent panel just for the garage and power tools coming straight off the incoming feed rather than through a primary panel), then almost certainly no. Generally, I would say for significant load hybrid or all-electric car charging you need minimum 150A household capacity, and commonly 200A if you have electric appliances (dryer, range, A/C etc) - and sometimes 225 or 250A for all-electric houses that use electric water and furnace and maybe dsauna/hot tub/pool or alot of exterior lighting as well.

You will need to research the peak and normal charging loads for your car (to provide to the electrician - should be in owner's manual) and then have electrician in to see if that panel - or even your overall household service - can handle that load. Many, many hybrid and especially all-electric car buyers are getting $3-5,000 and occasionally up to $10,000 or more nasty surprises when they find their household power system needs a major upgrade to charge their car - in addition to the typically $1200-2500 for the new circuit and outlet and charger.

Note - a few charging stations now come with a manual lockout on rapid charging that permanently (at least unless you open the casing up and reset it to high rate charging) restricts the demand to something more reasonable for a normal house circuit - though of course that means overnight rather than an hour or less to recharge, and if the car is used late at night as well as to commute might not even result in a full recharge overnight.

Note - there have been a few articles of people tapping off existing circuits with nominally OK but not oversized wiring or overloading panels to charge their car - with resulting fires, so do not skimp on this. I emphatically recommend, and would never do less than this myself, that you get a dedicated circuit witih slow-blow overcurrent protection at/in the charger (OEM or third party if OEM does not supply) so if there is a problem with the charger or battery it trips a separate breaker AT the charger, and does not count on the breaker box and wiring to it handling the overload. I also recommend at least a one and preferably a two wire size upgrade on the wiring - because the building codes and wiring allowances on household sized wiring and fixtures are not predicated on long-term continuous demand, so using normal household size wiring for the demand can result in both overheating at any nominally damaged insulation or iffy connections, as well as greater energy losses in the wiring than are necessary. I saw one article that the payoff for upsizing the wiring so teh demand does not exceed half the rated continuous capacity, in energy loss savings, runs about 5 years for all-electric car charging and a nominal 25' circuit length when done as part of the initial circuit installation - because you are paying additional only for larger wire and connections, which is a small pdercentage of the total installation cost.

I have read of cases where charger or battery failure has lead to surge loads of several hundred amps, which can cause almost immediate wiring/connection failure and possible fire in the house wiring or service entry, especially if you have a breaker failure in the breaker panel (not uncommon with older breakers), so I recommend the breaker panel breaker be used as a backup not the primary protection. There is some discussion in the electrical code contributor forums to make requiring overload protection at the outlet a code requirement in future code revisions, and many OEM's are now putting this sort of protection in the charger or car plugin itself (which in my opinion should always have been the case). Also - if getting a third-party charger - go with a good brandname, not some unknown brand from Home Depot or Lowes or Joe's Five and Dime. If you have ever seen a high-amperage fault throwing molten metal and sparks 10 feet and causing almost instantantaneous combustion and blowing-out of an entire wall drywall or siding section you will realize the benefits of upsizing the wiring and connection quality (though the breakers should be sized to the actual design load, not oversized, as that is what shuts off the power in the event of an overload. Consider also that this high-amperage load is commonly left on while you are sleeping - so equivalent safety wise to leaving a dryer or oven going while you are asleep - just an unnecessary risk in my mind unless you take measures to ensure against overload problems.

Answered 3 years ago by LCD

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