Re: @45RPM
"If it takes a kWh to do a job then it will, give or take, proportionally more time to do it with less Watts. You save nothing."
In fact, you'll be worse off. Depending on the quality of the insulation it loses heat whilst it's above room temperature. During the elongated time to boil it will be losing moreheat which will take more energy to replace.
Biting the hand that feeds IT
