Mind Your Units!
By Edward Ang
December 22, 2003
I had enough of these for the year and want to make
this clear before the year ends. We have to get the
units correct. Stop using Amp to refer to battery
capacity, kW or kW per hour to refer to energy etc.
It causes me pain to read a post that says something
"My EV uses 200W per mile."
This is like saying I run 5mph per mile. What?! It
should be 200Wh per mile.
"My charger puts out 3kW per hour."
I run 5mph per hour?! What?! It should be 3kW
"My EV takes 7kW to get a full charge."
It should be 7kWh. It would be nice if your EV
becomes fully charged instantly the moment your
charger puts out 7kW of power.
"My battery is 20A per hour." Huh?!
It should be 20 Amp hours. It would put out 20A for
an hour. So, it is Amp multiply by hours.
"I get 13kW per hour from my solar panels." What?
It should read 13kW if you are referring to peak
wattage or 13kWh if you want to say total energy
produced a day. There is no such thing as 13kW per
"I pay $0.13 per kW of electricity."
Although I love to pay $0.13 per kW no matter how long
I keep this kW going, I doubt that this is how your
power company charges you.