[tptacek]

Partly anecdotally and partly empirically: I have a Wattvision thingy on my meter, I use an electric kettle, and I cook lots of things sous vide (in water baths held between 130-160f for very long times). It appears to take drastically less energy to have a rice cooker keep 120 ounces of water at 150f for hours on end than it does to bring a kettle of water to a boil.

This makes sense to me. Watch the sous vide PID controller govern the rice cooker; it's only switched on for a fraction of a second every 10 seconds or so.

Water also has a high specific heat.