Quote:
Depends what kind. The heated dog bowl type are fairly low wattage if I remember correctly, maybe 60w??? and mine has a thermostat so it clicks on and off, thus you are not using that wattage *all* the time. Heated waterer bases for metal founts, or the plastic waterers with a heater built into the bottom, are more in the 100-120w range IIRC.
For whatever appliance you are considering, look at its label to find out what wattage it is; multiply by 24 and then again by 30 and divide by 1000 to get how many kilowatt-hours it will use per month; then multiply by whatever your local electrical rate is (cents per kW-hr). In some cases this will be accurate, in other cases (if there is a thermostat that switches it off a lot of the time) your actual bill will be lower.
With our rates here, a 250w heatlamp (or anything else 250w, such as a pair of 125-w heated waterer bases) costs somewheres around $30/month to run.
One thing you can do is to do, as you say, "the old switcheroo" when temps are warm enough that simply bringing fresh water in the morning will be enough to last all day, and only bring out the electrical appliances when temps get cold enough that you'd have to be ferrying fresh water out several times a day.
Good luck, have fun,
Pat