I purchased an EV in 2026 feeling great that I would be saving $$$ while oil prices are soaring. After driving and charging my modern non-Tesla EV for several weeks, I found out that there was way too much energy waste with Level 1 charging and nobody is talking about it much.
Level 1 Charging Efficiency Claimed on the Internet
If you ask Google or AI on Level 1 charging efficiency, it typically says 70-80% (some even say 80-90% efficient) efficiency for Level 1 charging and around 90% charging for Level 2. I roughly trusted that amount before buying an EV and it seemed most people on the internet or Reddit seemed to quote that a lot or they said the measurement / conditions were wrong if it was lower than that.
This could not be further than the actual truth.
Level 1 Charging – Main Inefficiency
Level 1 charging is typically done at 120 volts with a current of 12A. Theoretically, this would be 120 x 12 = 1440 watts of charging but a Level 1 charger charges slightly lower than 12 amps, around 11.3A. so that would make charging at 120 x 11.3 = 1,356 watts.
However, I was pretty puzzled when the EV charging screen said the car was charging at 900 watts. I expected it would be well over 1000 watts but it just wasn’t around there. It turns out, to charge the battery efficiently, the EV’s ICCU (Integrated Charging Control Unit) uses up a lot of power to condition the battery and charge the battery efficiently. A LOT more than you think.
So according to what the EV says it is charging the battery at, the efficiency seems to be calculated at 900w / 1,356w x 100 which turns out to be a 66.37% efficiency. This is clearly below the 70% to 80% efficiency mentioned, just to start with.
However, it doesn’t stop there!
There is more…. just because your EV tells you your battery is charging at 900 watts doesn’t mean that your battery is actually taking all of that power and storing it. By dividing the total watts the battery was charged by the number of hours it took to charge it, I came to a number of about 745 watts of actual charging. So we are losing about another 150 watts here.
If you combine those 2 losses, loss from the ICCU and loss from the actual charging, I was getting a charge of 744 watts while using (or paying for) 1,356 watts of energy. 744 watts / 1,356 watts x 100 = 54.87% efficiency!
The Numbers Don’t Add Up
The internet claims Level 1 charging is 70-80% efficient. Maybe this is based on a Tesla? I don’t own one so I can’t tell but maybe you can make your own measurements the way I did and come up with a number that you can share. Mine is made by Toyota and I assume Toyota would know a thing or 2 about batteries and charging so I wouldn’t blame my EV quality is too cheap.
What Are Your Numbers?
Please share them in the comments below while I go through my measurements and calculations on Level 2 charging as comparison!