Hi Jim,
I'm using an electrical kettle (hope that subscribes it..) and a digital thermometer. The thermostat of the kettle is not good enough at low temperatures, so using the clock and temperature on my digital thermometer, I keep track of the time it takes to rise 1 degree in temperature.
I know from experience that when I have to reach 32C with 20 liter of milk, I have to turn off electricity at 30C.