humming noise, but no water running

Hello
We havd noticed a few nights a ago that our boiler ia quite loud even at night when no water is being used. This might be the case during the day as well, we might not have noticed so far. Is this normal? We are currently not using the timer or peak time functions. Only the washing machine takes direct warm water' other than shower and taps.
This question might be very silly but we are afraid that it keeps boiling the water or uses power without doing anything and that this will effect our bill tremendously.

Many thanks

The Pulsacoil is design as a night storage water heater and is re heating the cylinder with the eco 7 night electricity. Over the time of use , yes this immersion can become a bit noisy, but this will not affect your energy consumption. Try some central heating inhibiter like fernox mb1. this mostly makes the system a bit quieter.
hope this helps regards Mario @ Mario's Boiler Service

Also have a quick look at the water level in the header tank. It should be roughly half way.