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Time. The pumps and circuitry have to stay powered up twice as long on 120v.
Conversion efficiency. There is a slight efficiency boost trying to convert 340vdc up to 360 to 400vdc to charge over 170vdc.
170vdc is about what you get from rectifying 120v, 340vdc comes from 240vac.
The same resistance losses for double the power. 12 amps is 12 amps, the wires don't care if it's 120 or 240. Assuming a both circuits run the same size wire.
It appears the biggest efficiency boost comes from reducing time the charging system stays powered up.
So a 16 amp 240vac evse will be more efficient than a 12 amp 240vac evse.
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1984 chevy suburban, custom made 6.5L diesel turbocharged with a Garrett T76 and Holset HE351VE, 22:1 compression 13psi of intercooled boost.
1989 firebird mostly stock. Aside from the 6-speed manual trans, corvette gen 5 front brakes, 1LE drive shaft, 4th Gen disc brake fbody rear end.
2011 leaf SL, white, portable 240v CHAdeMO, trailer hitch, new batt as of 2014.
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