In addition to everything else that is known, like:
Slightly faster battery degradation
There is one more thing that is often overlooked.
I have 2014 Leaf with 134Mm or 83k miles, lost 9% of capacity during these years.
I have always charged to 80% (except before longer trips). Very often went down to very low warning and dashes.
(PS: please do not try to be a battery health expert and tell me not to go that low, reread my capacity loss if you don't get it).
I've measured it few years ago and once again recently and got pretty much identical results.
Charging from 0% (dead battery, 0,3kWh) to 95-96% happens at full speed of 16A (standard onboard charger).
And charging from 95% up to 100% takes a lot of time.
Actually, I measured.
My somewhat degraded battery that can still fit 20.5kWh of capacity (instead of new 22kWh) needs just 6.0 hours to get
19.3kWh of energy. And another one or two hours (depending on balancing and temperature) to get that last 0.4-0,8kWh.
Charging acceptance drops like rock. But electronics are still running. And charging efficiency during that last hour is way
down... to around 60%, or even 50%.
And charging those 95%, or 19,3kWh, consumed 20.8kWh from meter. Therefore efficiency from 0% to 96% is 93%.
Total charging efficiency from 0% to 100% is no more than 89%
. And even less if battery is cold (less than 4 bars).
These 4-5% of extra loss all add up in all those years.
For me it would mean 6Mwh*0,05=300kWh, therefore around 30€ each year. Just a parasitic loss of energy
This same story applies to those who charge any slower than 16A at 230V (aka 3,3-3,6kW).
Do not charge slower than 3kW. Especially on 110V in US. At least that one is no secret.
This efficiency loss also applies to EU "trickle charger". Which runs at 2,3kW. It's still trickle, like my signature says
Also there is almost no efficiency gains with 32A charging AFAIK.
So anybody who charges up to 80% (or even continues charge right before departure) at 3kW rate has 7% loss (maybe 6% in case
wiring from main meter to EVSE is short). Anyone who charges to 100% daily can not get less than 10% of loss.