Conditions of supplyStandard Licence Conditions (SLCs) apply to all suppliers of electricity. A supplier is under a duty to offer you a contract containing standard terms and conditions that comply with its licence conditions – eg, SLC 22.3 provides that fuel will not be supplied unless it is done so under a domestic supply contract or a deemed contract. Once you sign a contract, you are legally bound by its terms, but if you think any are unfair or unreasonable, Ofgem has the power to stop a supplier enforcing any term which is incompatible with its licence conditions. See here for contractual terms and here for details about unfair terms.