From what I knew/know about Economy 7 it's an old style tariff set up to benefit storage heater users, which heat up at night, and then release their heat during the day. It means you can also do things like washing and drying at night, at a cheaper tariff, although unless you run a laundry, what is the point. If you are paying the bills there, and you don't have storage heaters, then ask the utility company to change tariffs.