I have two Satsuma mandarin trees in my front yard. They are inside their own little greenhouse which has a greenhouse thermostat which turns on two 40watt lamps (one per tree) whenever the temperature falls to 30F or below.

It occurred to me last week that there was an easy, cheap way to track how long the lights stay on / how long the temperature in the greenhouse is close to freezing: Connect an old analog electric clock to the same outlet that powers the lamps.
I set the hands for 12 as a starting point. When the thermostat turns on power, then the clock starts running, when the thermostat turns off, the clock stops running. In this way I can track exactly how long the temperature is below 30F, How long the lamps are on, and my electricity usage.

What a neat idea. With only two 40 watt lamps, the electric cost should be next to nothing no matter how long they are on. - Millet (404-)

yes, that's an inventive approach, indeed... i always go green, whenever i can, so i like your idea!

take care,
igor

wow that is exactly what I have been trying to think of. I have never had any idea how long my heater runs and this would take care of that. Now if I can find one of these clocks somewhere.

Mike

If you want to keep track of the hours you can use a 12 volt transformer wired to a hour meter for a lawn tractor and it will keep up with the hours for the entire winter. It must be plugged into the thermostat with the lights. It won't make your power bill any cheaper but you will know how many hours they were on and you don't have to wonder how many times the hour hand went around at the end of the week or whenever you check it.