Does it cost a lot more to keep the electrical immersion heater on constantly for hot water during the Summer?

Question:Has anyone done this and recieved the electricity bill afterwards? Is it a bad idea? I figure all it does is constantly heat up a bit every few minutes rather than a big heat up every so often... can't cost that much can it? Would be so convenient in the Summer but I am scared to. Please help.

Answers:
I've only used electrical immersion heaters in aquariums. It all depends on the cubic feet of water needing to be heated. For my very big aquarium and the circulation in it, it was more efficient to have two heaters as they cycled less.

Now, if this is for a pool, how often are you using it? How long does it take to heat up? If you only use it on the weekend, you can turn it down (but not off) when not in use and then turn it back up to normal. The really wealthy guy at work (who let the back office use his family's vacation home periodically), they had a timer set since, unless someone was actually on vacation, the pool was only used on the weekend. It was set to turn up on Friday morning, so was plenty warm by the time arrivals were ready to use.