What is core capacity and why consider it? These two sister reports by CAG, in association with Professor Jacopo Torriti and Doctor Timur Yunusov, will enlighten you. Citizens Advice and Scottish and Southern Energy Networks (SSEN) both wanted to explore the concept of core capacity mooted by Ofgem as part of its latest review of network access rights and charges. This postulates an amount of electricity capacity that meets basic household needs, and in so doing introduces capacity – as opposed to energy – as something that consumers might need to start thinking about. Capacity is when you plug in one too many gadgets and short the household fuse – in that moment, its too much power. Energy is how much power you use over time. We’re getting better at thinking about how we use energy – not least because we pay for every unit of energy we use – but what about capacity? Its important because how much capacity we use determines how engineers size (rate) the network which in turn determines how much it costs. And we are going to be using more capacity in the future – for example with the growth of heat pumps and electric cars. We consider how we might set a core capacity, look at international experiences in setting capacity limits and capacity charges, and analyse smart meter data to understand how much capacity we use and what drives this.