Who is responsible for the electricity charge of tap water booster pump?

The booster pump in your community must be property management. According to your description, the property can't receive the property fee, so it can't pay the electricity fee, so the booster pump only runs for a few hours every day.

This phenomenon is definitely abnormal and unreasonable. If you take legal channels, the object of your lawsuit should be the property management company, because the property management company failed to perform its services. If you complain, you should ask the government (whether there is a mayor's hotline or something) to reflect the problem. Another way is to set up an owners' committee in your community, but you have to pay a fee to maintain its operation.