In the long term, as the world's finite reserves of natural gas and oil become depleted, the present pattern of energy consumption will become subject to extensive substitution. It is electricity that holds the key to this potentially complex equation. This article deals with the contribution that electricity in general and nuclear power in particular can make economically to the UK energy needs, as the indigenous oil and natural gas supplies begin to run down and their prices increase further in real terms. It also examines the timescale on which the additional generating capacity could be built.