I don't see what that has to do with efficiency though. Granted gas is probably easier to modulate for spiky usage—I've seen the same BBC documentary that I su

I don't see what that has to do with efficiency though. Granted gas is probably easier to modulate for spiky usage—I've seen the same BBC documentary that I suspect you have, with the quip about France having to donate some capacity to satisfy the post-EastEnders surge—but that doesn't really tell us anything about efficiency per se. Having used both kettle technologies, my gut feeling is that heating a traditional kettle on gas just wastes a lot of the heat into the air by forcing the heat to penetrate an intermediary layer, whereas an electric kettle is insulated and puts heat directly into the water. This isn't a problem if you are boiling water to heat radiators because the lost heat is still helping heat the house. In that case you are saving the losses of converting heat to electricity (at the power plant) and then back to heat (in an electric heater).