Mark DuVall of the Electric Power Research Institute (EPRI)
"If was pointed out that daily charging of the Chevy Volt will increase the typical single family home electric usage by about 25%. The electric draw is less than that of a refrigerator/freezer or central air conditioning system."
The Volt will take less electricity than the fridge and freezer? A typical modern fridge in the UK takes 300kWhrs per annum, a freezer 200kWhrs per annum. This give a total of 500kWhrs per annum, or approximately 2kW per day. We can double this to allow for the USA propensity to have everything bigger but not necessarily better. So, at 1000kWhrs per annum, this works out at approximately 3kWhrs per day.
If we assume this 3kWhrs is used with 100% efficiency to charge the Volt and is delivered to the Volt propulsion system with 100% efficiency, this means it will travel for 40 miles at 40mph using 3kWhrs. As 1hp is 746W (roughly, depending on other issues: http://wikicars.org/en/Horsepower) we can approximate this to a 4hp engine.
So, GM apparently have found a way to power a family sized car 40miles on the equivalent to a 4hp engine. Why did they bother with the electricity cycle part of the vehicle? They could have simply put in a moped engine, a motor mower engine or even a modified chainsaw engine and probably got even more mpg overall.
Once more it seems that GM are making spurious claims. However, it IS totally possible to charge the Volt for less than the energy used by a fridge and freezer. Just don't expect to get more than the end of your street and back, or as GM would put it "the end of your block".