There are two ways the psi can raise in your home. If you have a closed system, one with a pressure regulator valve, and no expansion tank, then when the water heater heats, the expanded water has no place to go and the pressure rises. This will trip your T/P valve on the water heater is the pressure reaches 150 psi. If you do not have a closed system, then the city water pressure is fluctuating. I'd suggest a new pressure regulator and an expansion tank to deal with the problem.