What are the Capacity Market Rules? The Capacity Market (CM) was introduced by the UK government to ensure there is sufficient commitment/investment by the private sector in providing reliable electricity capacity, so as to ensure security of electricity supply in Great Britain (GB). Following lengthy consultation, the Capacity Market was implemented pursuant to powers in the Energy Act 2013 (EA 2013). As set out in further detail below, the primary implementing legislation of the CM is the Electricity Capacity Regulations 2014 (Capacity Regulations), SI 2014/2043 (as amended). However, in addition to the Capacity Regulations, SI 2014/2043: • the EA 2013, s 34 grants government (by way of the Secretary of State) the power to make and amend ‘Capacity Market Rules’ (CM Rules) to supplement provisions in relation to the CM made under secondary legislation, and • the Capacity Regulations, SI 2014/2043, reg 77 permits the Gas and Electricity Markets Authority (GEMA) to make/amend Capacity Market Rules about the operation and administration of the CM. In practice, GEMA exercises this power through the Office of Gas and Electricity Markets