I live in a mobile home and in one end of the house I have noticed that the cold water is luke warm and does not run cold. Last night the outside water hose did the same thing. My electric bills are outrageous! What is it; the water heater??
There are different possibilities why this may be happening.
One is that if you are on public water and the pressure is too high, and a Pressure Reducing Valve has been installed on your main water supply line without an expansion tank near the water heater to control the hot water expansion back into the cold water lines.
Solution: Add small expansion tank.
Another is that there may be a faucet that is faulty somewhere in your home for some reason, allowing hot water to expand back into the cold side through the faucet body.
Solution: Go through the process of eleinination and repair or replace that faucet.
Others here may have additional suggestions.