I have been using this brand timer on my Hot Water Heater since 1983 in every house I've owned including ones I rented out as well as my daughter's first home. She has gas HWH so not really appropriate. All together I have personally installed 6 of these! MAKE SURE THE MAIN BREAKER IS OFF!!!Also, there are 2 kinds of Little Gray Boxes available. One is for 110, the other is 220. It's in the fine print. If it's under $100, it's probably a 110.By putting this in my first house, I was able to drop my electric bill by $100 or more. We found that the HWH temp was set too high and it darn near had to run 24/7. With 4 ppl in the house (2 Teens!), I was able to set 3 periods of 2 hrs each. Perfect for baths and dishwasher as well as avoiding peak usage hours. Laundry day, I flipped it on as needed.I just built a duplex for my daughter and me. All electric and both HWH have these installed. I can't say enough good things about this brand. This last one I bought was for a friend who had put another brand on his HWH several years ago and it wasn't working anymore. He is tickled to death with this one.