The easiest and cheapest solution is to adjust the hot water heater so it’s set at a maximum of 120 degrees. Read the manual for the hot water heater carefully, and follow all safety precautions before opening it up. There’s a lot of voltage in those things. (You might want to have a plumber do this.)
The next line of defense is an anti-scald faucet or showerhead. These devices automatically detect water temperatures that are unsafe and shut the water flow down to a trickle. I don’t actually know how they do it…
I like the idea of doing both. Turn down the water heater (saves money and the environment as well) but also install the hot stop showerhead in case something goes wrong with the water heater. (I once had a hot water heater with a malfunctioning thermostat. It sometimes got extra hot and sometimes not hot at all.)
Is this an issue you’re worried about? What other solutions have you found?
Photo: Courtesy Kreative Eye Photography via Flickr (creative commons license)