An extra 1KW would actually charge the car given time. Not just keep the battery warm. 1kwh is supposedly about 4 miles. Charge for 12 hours overnight, you have enough to get to the supercharger.
In the OP story, the car was losing charge while plugged into 110V outlet, that means that 1.5 kW was not enough to keep the battery warm. An extra 1kWh might or might not get it into actually charging and even if it's been charging at 1kW it would not get 4 miles per hour, the car driving in these conditions would still use energy to keep the battery pack at the working temperature.
On a side note, I find it amusing when Brits try to brag about their superior electricity due to the progressive 240V. People living in the houses wired in a ring [1], which set themselves ablaze when they try to turn on AC, in my imagination would be more reserved ;)
On a side note, I find it amusing when Brits try to brag about their superior electricity due to the progressive 240V. People living in the houses wired in a ring [1], which set themselves ablaze when they try to turn on AC, in my imagination would be more reserved ;)
1. https://en.wikipedia.org/wiki/Ring_circuit