I think a 25% reduction in range is nothing to brag about. Last I checked, my gas car gets a 0% reduction in range in cold weather.
But I am actually more interested in how hot weather affects it. I know for example that a Volt owner manual states not to leave the car out in the sun without being plugged in....energy is needed to cool the batteries. So I wonder what the extra drain would be to keep both occupant and batteries cool in hot weather....not California hot but hot and humid 105 degree days in the midwest and deep south.
A typical gasoline cars gets a 12% range reduction in cold weather.
http://www.fueleconomy.gov/feg/coldweather.shtml
“But I am actually more interested in how hot weather affects it. I know for example that a Volt owner manual states not to leave the car out in the sun without being plugged in....energy is needed to cool the batteries.”
The manual does not say that. It says to use sunshades when parking in direct sunlight when it is hot.
“In hot weather, avoid parking in direct sunlight or use sunshades inside the vehicle.”
It is common knowledge among EV owners that cold weather hurts electric cars range much more than hot weather does.
(As long as you are not talking about the Nissan Leaf, which went the cheap route among mainstream electric cars and did not include active liquid cooling for their battery. As a result, early model years suffered some permanent range reduction from the heat in Arizona. They have addressed this issue in recent years.)