How do you tell if it uses a lot of energy or little? More specifically, do food dehydrators use a lot of energy? As they have to be on for long periods of time. Relative to other kitchen appliances do they use a lot or little?
Electricity is metered in killowatt hours. 1 kWh is equivalent to using 1000 watts for one hour. A powerful hair dryer might use 2000 watts so using it half an hour would use 1 kWh. A laptop might use 50 watts while being actively used so it would take 20 hours of use for it to use 1 kWh (when not in use most laptops go into power saving standby, sleep or hibernate modes). In most of the US electricity costs from $0.10 to $0.20 per kWh. In remote or urban areas it can be over $0.40/kWh while some locales near hydroelectric plants pay only a nickel. It is hard to say exactly how much power a dehydrator uses; they have thermostats so it doesn't draw current the whole time it is in use. Mechanics have a saying, "One measurement is worth a 1,000 expert opinions." There are small kWh meters for appliances. Kill-A-Watt is one brand. If you plug an appliance into one of these it will tell you how much power it consumes. Power meters usually pay for themselves by helping consumers use electricity more wisely. You can buy or build a solar dehydrator. All these require is a sunny day to do the job.
Larger appliances have an "energy rating" sticker on them. The higher the rating, the better. any appliance manufactured within the past ten years or so (maybe longer) is going to be about the same and have a high rating. Small appliances such as the dehydrator, coffee pots, ect are notorious for using alot of energy because the are "on" all the time when in use and there is really not a good way to make them efficient.