[Redbob]

1 HP is roughly equal to 750 watts
To drive the Volt at highway speeds takes say 10 HP minimum, or 7500 watts.
You run it for an hour, you’ll have to put that much energy back into it, 7500 watt-hours.

That’s the equivalent of running your 150 watt outdoor light for 50 hours (!) - and these are VERY conservative figures that don’t take charging efficiencies (or lack thereof) into account.

[Redbob]

A more likely scenario is that all those figures are doubled: 20 HP -> 15 kW-hr per hour of operation.
At California’s 2010 average residential electricity rate of 15 cents per kW-hr. this is then about $2.25 per hour of operation.
Not a bad deal, actually.

[Lockbox]

and these are VERY conservative figures that don’t take charging efficiencies (or lack thereof) into account.

1st start with the conversion of coal or natural gas into electricity, with natural gas being the most efficient at 50% of the possible energy converted into electricity. Then add in the following losses, 6.5% for transmission, 3% for transformer and 10% for the charger.