Gas and electricity companies supply energy to homes and businesses, usually through agreements that set out the tariff, payment method and contract terms. They bill customers for the gas or electricity used, based on meter readings or data from a smart meter, and may offer fixed-term or variable tariffs. Some suppliers provide gas and electricity together, while others supply only one type of energy. Customers can generally expect account support for bills, payments, meter readings, moving premises and questions about their supply. Suppliers may also arrange smart meter installations and offer tools to monitor energy use, alongside options such as electricity tariffs linked to renewable generation. In Great Britain, energy suppliers are regulated by Ofgem, which sets rules covering matters such as customer treatment and supplier conduct. Companies that deliver energy through pipes and cables are separate network operators, rather than the supplier customers choose for their account.