See the little green light? That means it's all heated up. When the light turns orange, it means it's in the process of heating. If the light is orange, we know not to run the electric kettle, the stove, and/or the oven, because the combination will (and frequently does) blow the fuse.
I like the little sticker next to the green light. It tells you what to do if something bad happens.
No light equals sad face. Telephone arrow fat guy with wrench!
Several people (notably our landlord and the people who rented this apartment last year) have suggested that we can save energy (and save on our energy bill) by turning the hot water heater off during the day (when electricity is more expensive) and turn it back on at night. The tank holds enough hot water to allow for our showers and dishwashing, so there's no problem there.
The problem, as Maggie discovered with a little online research, is that shutting off electric water heaters lowers the tank's water temperature enough to encourage the proliferation of a bacteria called Legionella, which can cause Legionnaire's Disease. (Heaters using fossil-fuels are not at risk, for whatever reason.) Legionnella mostly seems prevalent in non-municipal water systems, and can only be eradicated if the tank temperature is set to 140 degrees Fahrenheit or higher. This creates another problem, since 140 degrees can scald pretty badly. Our water is certainly municipal, and Legionella seems mostly to affect those with already-compromised immune systems. So it's hard to tell just how seriously dangerous it is to turn off our water heater.
For now, au cas où (just in case), we're keeping the water heater on. But we'd love to hear from anyone who has experience with this kind of thing, or happens to know anything about the issue.