Energy Star chargers

Energy Star chargers

I just received a note from my electric company strongly recommending that I buy an Energy Star charger for my car. They claim that non-Energy-Star chargers waste a lot of energy when idle, i.e. when not charging.

I haven't been able to find anything about whether my original charger (from 2012) has this problem. Does anyone know?


ArthurG | 22 mai 2019

P.S.: My charger is the original Tesla charger.

andy.connor.e | 22 mai 2019

If you're worried about that, throw your breaker when you're not charging. I would try to find out what kind of power drain the Tesla charger has before you consider buying another charger, because it smells like BS to me.

T35LAX | 22 mai 2019

I suppose BS stands for Best Solution :-)

andy.connor.e | 22 mai 2019

Sure. I went to energy star website about EV chargers, and they say energy star chargers use up to 40% less. Key word: "Up To 40%". But if the charger is using 10W while idling (which is really quite alot), 40% less which is the maximum indicated on their website, thats still 6W.

Thats why i say to figure out what the Tesla chargers idle power draw is first. Because in this scenario, you would have spent all that money to have an energy star charger installed, to save 57 cents per month. ($0.20/kWh)

Dramsey | 22 mai 2019

10W is "quite a lot"?

No. It's not. It would be barely enough for a tiny reading light. When I'm charging my Model S at 50amps on a 240 volt line, that's 12 KILOWATTS. At 13 cents per kilowatt-hour here in Nevada, 10 watts of wasted power would cost me a less than a dollar if the charger sat idling for a month.

All that said, we really don't know what the Tesla charger's idle power draw is.

andy.connor.e | 23 mai 2019

"It would be barely enough for a tiny reading light."

Depending on what kind of a bulb you are using, i can get an 800lm LED bulb drawing 9.5W. Yes, it is alot for idle power drain. Why are you comparing idle power drain to light bulb usage? I dont really get that kind of comparison.

Doesnt matter how much power something draws with load. Full load power has nothing to do with idle power draw. And yes thats correct, as i stated, 10W of wasted power costs about 57 cents per month. Again, thats why i said to check what the idle power draw is before you start going out and spending money on new chargers.

EVRider | 23 mai 2019

Or turn off the breaker like @andy said earlier. Problem solved.

greg | 23 mai 2019

I think the missing word on the Utility companies claim is the word "can".

As in:

"non-Energy-Star chargers CAN waste a lot of energy when idle."

And also (not stated) by your utility company:

"EV chargers CAN ALSO waste a lot of energy when CHARGING"

Energy Star ratings are usually pretty vague about what the Energy Star is actually awarded for.
You can't easily look up exactly what the product is so superior and efficient for that it deserves a star.

In the past, often the Energy Star rating only covered the *stand by* or idle power efficiency.

Whereas the main issue to consider is the amount of wasted power the EV charger uses when the charger is running.

As not all chargers are equally as efficient at converting and the delivering the incoming energy - which is what you pay your utility company for, to the energy that goes into battery of the EV.

And there can be many causes for this.

You'd have to think that a Tesla wall charger would be matched to work with their cars better than some non-Tesla charger, and also, have low stand by power drain as well.

However, its certain a 7 year old Tesla Charger might not be as efficient as one sold today. So yeah upgrading to a newer Tesla one might be an option. But realistically, its hard to know. You can measure this usage by using special tools. But the energy savings probably wouldn't make it worth the money to replace the old one with a newer one.

I recall 15 or years ago Energy Star ratings suddenly started turning up on Plasma TVs. WTF!?

All proudly proclaimed that this or that TV was an "Energy Star". Again WTF!?

Turns out that the "Energy Star" only applied to stand by power.

And never ever considered at all, the power use for when the TV was actually running.

And as we know [or should know], Plasma TVs in use were the TV equivalent of gas guzzling H2 Hummers and then some. Yet the worst power hogs for these TVs were still getting slapped with "Energy Star" labels, when the adjacent flat screen TV using LED/LCD on display beside it would have used and wasted a lot less energy over its lifetime than your Plasma used in a year.

But you'd never know if all you did was take the "Energy Star".product.

All up, that was a bit like giving a H2 Hummer an Energy Efficient label - just because it used very little fuel [so had a high "stand by" MPG] when it wasn't running. But not considering its MPG when its running.

Key thing is that "energy efficient" means a *lot* of different things to a *lot* of different groups.
And what they mean by Energy Efficient and what you mean by it may not be the same thing.

Short answer is - you gotta do your homework. If you can't be bothered or can't find out.

Do as others suggest and simply flip the circuit breaker. Problem solved.

ArthurG | 24 mai 2019

Thanks for all your replies. My local power company, PG&E, includes inserts with my bills comparing my energy use to that of "similar homes." They never define "similar," so I don't know for certain whether they're comparing mine only to other houses with electric cars. Still, they frequently say I use more power than similar homes, and I'm guessing that they included the Energy Star charger message because they know I have an EV.

In any case, I'll do some research to see whether my old Tesla charger is efficient. That will be easy to do when the car isn't charging, but harder when it is. I suppose I could compare my house's electric meter rate to the rate at which the car is charging and see how much loss there is.

andy.connor.e | 24 mai 2019

Saving 40% of idle electricity usage will never offset hundreds of dollars to install a new charger. Hope you find your answers though. | 24 mai 2019

Ok, I actually tested the idle current of the MC, and it was under 100 mA (the bottom limit of my measuring device). That's less than 1 KW/h in a year. In most places 1KW/h costs less than $0.40. A typical 4W night light takes 40 times more power. | 24 mai 2019

On to Energy Star - This is a voluntary program that some vendors use. Looks like Tesla never bothered to submit to getting the Energy Star label (and the costs involved). I suspect they would qualify.

Next - Charger - The charger is inside the car. There are no options to remove it and replace it with something else. There is an EVSE (Electric Vehicle Supply Equipment) that is often called a charger, but is not. This is the device that connects the 240VAC to the vehicle. Most non-Tesla EVs require an expensive EVSE, and some are better than others. Tesla doesn't require this at all, and the MC connects to a NEMA 14-50 (and other receptacles) eliminating the need for an EVSE. The optional Tesla HPWC is sort of an EVSE too and uses very little power while idle - likely under 100 mA (although I haven't measured it). Lastly, you can buy and EVSE and use Tesla's included J1772 adapter, but I can't see why anyone would bother unless you also have a non-Tesla EV that requires an EVSE and you wish to share it with your Tesla.

milesbb | 25 mai 2019, check your math. 100ma at 240 volts is 24watts. I get 8.6 kWh for a month. $0.86 if you pay 10 cents per kWh. | 25 mai 2019

@milesbb- Thanks. yep, I blew that one, but I was using 120 VAC (using a cheap plug-in monitoring meter). So 1/2 of what you came up with (i.e. 12W max).

I'll try and get a better measure of the current, but I'll have to take apart the electrical panel to get a current probe on the conductor. | 25 mai 2019

Ok, used a clamp on meter on the 240VAC connection for more accuracy. | 25 mai 2019

It's under 5 ma at 240 VAC, or 1.2 W max. | 25 mai 2019

Could be less, as it's at the limit of my clamp on meter. | 25 mai 2019

So the worse case is 1.2W * 24 hours * 365 days = 10.5 kW/h. So using $.40 kW/h (a very high rate), an idle cost of less than $4.20 per year. At $0.10 kW/h (common in some areas), the cost is less than $1.05.

@milesbb - check my math too :) | 25 mai 2019

Sorry for the split up post - forum was having problems with the text and wouldn't let it all appear together.

Tesla-David | 25 mai 2019

I have two HPWC's for charging our two Tesla's (MS and M3) coupled with solar + 2-PW2's to store excess solar, operating in self-powered mode, and monitor our electric usage every day, and do not believe that I am seeing excessive energy usage from our chargers when not in use. We are currently producing all our electricity with no grid energy usage since mid-February, exporting the bulk (70 percent) of our solar back to grid after supplying our all electric home, and charging both cars.

ArthurG | 26 mai 2019

Okay, you all have convinced me. I'm not going to bother doing any more research. It seemed unlikely that Tesla would screw this up, but PG&E got me worried.

Thanks to everyone.

jordanrichard | 27 mai 2019

Ummmm, why are people buying or looking into buying third party chargers? Your car has a built in charger and all you need is an outlet.

Dramsey | 27 mai 2019

Well, all you need is a NEMA 14-50 outlet on a 50-amp, 240 volt line...(using a 120v outlet isn't really practical for most people)

But seriously, there are several good reasons to get a separate wall "charger", Probably the main one is convenience: if you don't have a wall charger, you need to use your mobile charging kit (which I assume is still delivered with each car, although frankly it would not surprise me to learn that it had been made optional). This means it likely won't be in the car should you need it on the road.

Second, a wall charger (on a dedicated high amperage line) is the only way to get more than 40 amps/240v charging. I understand that current Teslas have been gelded to 48amps max charging (non-Supercharger), but the older cars can charge at 72 or 80 amps, and while I don't need "fast charging" often, it still does come in really handy every now and then.

DAlexModel3 | 28 mai 2019

I plugged my Tesla connector (110v) into a Kill-a-Watt meter; according to the meter, the connector consumed about 1 watt when not connected to the car.

reed_lewis | 28 mai 2019

The wall unit has no efficiency issues whether it is a J-1772 or a Tesla unit. The wall unit is merely a glorified switch which turns on the power to the car when conditions are right for moving power to the car is satisfied.

100% of the power (less the small amount required to operate the unit) goes directly to the car. It is a relay.

So no wall unit is more or less efficient than any other one. The only variable is the standby power required to operate the unit. This is most likely the same amount of power used whether the unit is allowing power to flow or not. Although maybe a little more because the relay is energized which requires power.

andy.connor.e | 28 mai 2019

Glad someone had the equipment to measure it. I couldnt imagine that the power draw was anything significant.