Installing electric car charger at home cost

The size of your circuit breaker box and service will decide how much it costs to add an electric ... [+] car charger.

Earlier, I wrote a guide to help you decide what range of electric car is for you, particularly with the Tesla Model 3. After you get your car, you want to install home charging for it where you park it (ie. your garage or driveway.) If you can’t install any charging at all, because you park on the street or in an apartment parking garage, then you face a challenge. If you can charge at your office (often for free) that’s great, though not without other issues. If you can’t do either, I don’t currently recommend purchase of an electric car, at least for now.

But you may find when you call an electrician and ask to install a nice Level Two charging station with a 50 amp circuit that they present a very expensive estimate — perhaps $5,000 or more — because you will need to upgrade the electric service into your home. Older homes often have only 100 amps of service, and electrical codes don’t let you exceed a given quota of devices and loads on them. Without going into the full formula, if you get 80 amps worth of 240v devices on a 100A panel you probably go over the limit. If you have things like a 30 amp dryer, a 30 amp electric oven, or an air conditioner or pool pump or other such device, you can easily go over the limit. Your electrician will tell you that you need to bring in new service from the power company (typically 200 amps) as well as whole new power panel. On top of that, they will need to run a line capable of 40 to 50 amps to your parking spot, and install a 50 amp plug (cheap) or hardwired wall EVSE (”charger”).

If you have newer service, fear not, you don’t need to change the panel, and you can just add a new circuit. If the wire is not that long, getting that plug may not cost that much. Sadly, many see a more expensive estimate. How can you get away from it? The answer is that while it’s nice to have enough power to recharge a car from zero to full in one night, you don’t actually need nearly that much.

Charging at Level One

The average car is driven only 40 miles/day. The Level One charger (which usually comes with almost any electric car) plugs into a dedicated standard house plug, and can deliver 12 amps. This means it will deliver 40 miles in an 8-hour overnight charging session. Most people have their car at home for much more than an average of 8 hours. So generally, even with this very slow charging, you will keep up. On the days you drive more, you won’t recharge fully, but as long as you don’t keep doing long days several days in a row, you will eventually make it back. (How quickly depends on whether you must limit charging only to off-peak electrical times.)

(If you are one of those people with a 100 mile commute, this is not going to work for you, and you may have to bite the bullet and get a new electrical service. But most people don’t go that far.)

Of course, adding 50 miles/night, sometimes you won’t have enough. For many, these times will be just a handful per year. Then, the fast chargers like Tesla superchargers can be your solution. This is OK if it’s not a common event. Other solutions can include charging at work. If you don’t commute, or have a round-trip of 20 miles or less, this solution will actually probably work for you — and it might even be free if you have a dedicated circuit plug in your parking spot. It has to be dedicated — nothing else on that circuit breaker.

One the left is a standard wall plug able to do 15 amps. The one on the right can offer 20 amps

In some cases, the dedicated plug may actually have a 20 amp breaker and 12AWG wire on it. In that case, the plug may already have the “T” slot in it that says it is 20 amp. Get the 20 amp plug (which Tesla sells and some other chargers sell) and you will see 50 miles or more in an 8 hour night, and you’ll definitely catch up with average driving.

At first blush, when you read that charging a 250 mile range car on Level One can take over two days you will think Level One is ridiculous, but in reality, the bigger the battery the more it can take the swings up and down and still leave you with enough capacity to do your driving. It’s the small battery car that absolutely needs to get to full every night. The large battery car doesn’t.

It should be noted in very cold climates this slow charging may not cut it due to the need to heat batteries and the larger drain of driving in the cold.

Charging at slower Level Two

A Level Two circuit runs at twice the voltage and usually at higher current. In fact, you can install these able to do up to 80 amps. For most people though, you don’t need nearly that much. You will be very happy with enough to restore about 60% of your battery, because your typical daily cycle should run from 20% to 80% full. On a 240 mile Tesla Model 3, you can get that in 8 hours with just 5 kw, which is what you get from a 30 amp plug, the same one that runs your dryer. (On any plug, the car charges at 80% of full current, in this case at 24 amps.) Such a circuit is going to fully restore you on almost any day you drive, particularly if you have more than 8 hours at home. You really don’t need it faster. The regular range Tesla can’t take more than 32 amps in any event (ie. a 40 amp circuit) but you just don’t need even that. If you can get it, of course you should take it, but you should not spend thousands to get that extra boost.

Your electrician might tell you you need a new panel for a 50 amp plug, but that you can put in a 30 amp or 20 amp without a new panel — which can save you a fortune.

That 20 amp Level 2 charger will recover about 14 miles for each hour you charge, or around 110 in an 8 hour night. That’s more than enough for most people — again remember that the average car does 40 miles per day. You will find a few days or stretches of days when you don’t get full, but you might find only a couple of days a year that the supercharger is called for. Again, you don’t want to be slow, but if it will save you $3,000 to go with 20 amps instead of 50 amps, then do it. Ask your electrician to install a “6-20” plug which has 240v at 20 amps. It uses a horizontal pin (like the 20a pictured above) but on the other side. Get that adapter for your car.

If you have a truly dedicated plug (it is the only thing on a breaker) then in many cases an electrician can, for not much money, replace a regular 120v socket with a 240v stocket for twice the charging rate, changing the plug and breaker as long as the wiring is rated for the higher voltage. Ask about that — it can almost surely fit your panel’s load maximum. (While the USA runs on around 120v for normal plugs, and much of the rest of the world runs on 220v, US homes can install 240v plugs and there is a well established standard for doing it.)

Sharing with your dryer

Most houses have a 30 amp electric plug for your dryer. It may be easy for you to switch to a natural gas dryer, particularly if you are in the mood for a new dryer. They cost only a little more, but they cost a fair bit less to run, and as such they save money in the long run. They also cost the same day and night. You do need to get a natural gas line at your laundry room. Adding that can cost real money — or be cheap — depending on how far it has to come. Perhaps you can even sell your electric dryer to somebody on Craigslist.

If you do this, you remove 30 amps of load from your house, and now you can add a 30 amp line for your car without needing a service upgrade. Your electrician can also in some cases just run a line from where your electric dryer plug is (was) to where your car is. This is more than enough power for your needs, and even though a new gas dryer is not free, it can be the cheapest option of all.

You can also buy a device called a “Dryer Buddy” for about $350 which lets you plug your car and dryer into the same plug, if your car parks close to your dryer. This device simply sees when the dryer is on, and shuts off car charging when it is. This is also a relatively cheap solution. Unless you run your dryer after midnight you won’t even notice sharing the plug.

A smart charger

In truth, while the electrical code demands that your house be able to handle everything being turned on at once — dryer, oven, air conditioner and car — the reality is you never need to actually do that. If car chargers were smart, they would come with circuits which detect when the other devices are on, and reduce or stop car charging when that’s happening — which is a very rare event. Such chargers would let everybody install car charging without a service upgrade. Sadly, they are not yet to be found. There is a device made in Canada called the DCC-9 which can go in your electrical box and it shuts off power to the charger when other appliances are on. Sadly, it costs around $1,000, when this is something that should come for almost free in the charger. But that can be much cheaper than service upgrade. Some day this technology may become lower cost and easier to install. An open source device known as SmartEVSE is able to do this but requires some more advanced set-up knowledge.

What about the high end?

This advice is for those with a 100 amp service in their house. If you have larger service, like 200 amps, there is no reason not to install a nice circuit to a 50 amp plug, known as the 14-50 plug — the same one big RVs use. You can’t use all of it, but you might buy a bigger electric car in the future, and you might even buy two electric cars, and wish you could get 60 or more amps. Price out getting bigger wire than you need, it may only add a modest amount to the price of your install. Tesla Wall Connectors have a nice feature which allows them to “daisy chain” and share the power between two of them when you have two Teslas.

Even if you go for one of the cheaper plugs described, like the 6-20, you should run thicker wire to it able to handle 30, 40 or 50 amps. Price it out. If you do, and later you do upgrade your house service, you won’t need to rewire that circuit to get that maximum power.

Of course, there can be other reasons to increase the service on your house. It’s a bit safer, and can offer room for other expansion you might do in the future, such as more cars, air conditioning, a hot tub and other things. All those reasons might justify the upgrade — the main point of this article was to examine when the car alone doesn’t need it.

By the way, if your employer gives you free charging at work, then of course take advantage of that perk. It may mean a bit less convenience when you park, or it may mean a premium spot. Even so, you should still have at least Level One at home, since that’s cheap. That will keep you boosted on weekends and holidays.

When you charge

Your power company may offer you “time of use” billing for power. This means that instead of paying a flat rate all day, you pay higher rates at peak times (usually afternoons and early evenings) and lower rates at off peak times (nights and sometimes mornings.) It all balances out except when you can move power usage to the off peak time. If you charge a car at night, that’s just what you do, and this is a big win for car owners. In fact, in California and some other places, owners of electric vehicles can request a special “super time of use” rate which is even cheaper at night and only available for EVs. The good news, if you get this rate, is you pay a very low price at night for your car. The bad news is that the rate in the day is quite high, and you will want to avoid things like running the dryer then. If you do a lot of air conditioning it may not be a win, but it usually is.

The other downside is that you don’t charge your car during the peak, so that if you do only have Level One, there will be fewer hours in the day you can recover. If you can charge 24 hours a day, even Level One can add a lot of power per day on the days when the car stays at home.

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