Electricity bill tarriffs

Good Morning

I have just received Endesa Única option to fix our tariff of electricity for our apartment calculated on past use , basically  . In England with the volatility of fuel prices , it is not advisable to change tariff . Would it be cost saving here though ? We fixed it some years ago I believe, but seem to pay even when we haven’t used the apartment , perhaps that would be a standing charge . I have never been able to understand the workings of this bill !!

By the way just seen that the particular tariff we have at the moment is Oneluz.

Any help or advice . I would be grateful.

Thank you Jane