Solar panel installations per year

Solar panel installations and the price of a pint of lager in the UK rose together between 2010 and 2022 with a correlation of 0.9735, which is either a remarkable coincidence or evidence that British pubs have been secretly funding the renewable energy transition through markup on Carling. The causal direction is, in the technical sense, completely unknowable, but pub economists have long suspected that expensive beer drives people outside, where they notice the sun.

UK pint prices rose from around £2.80 in 2010 to over £4.50 by 2022, driven by inflation, rising pub operating costs, business rates, and post-Brexit supply chain friction in the hospitality sector. Solar panel installations grew over the same period from a few hundred megawatts annually to several gigawatts, driven by Feed-in Tariff subsidies, Contracts for Difference, and dramatically falling panel costs from Chinese manufacturing scale. Both are upward-trending series over an eleven-year window, and eleven years is enough time for two independently motivated trends to look like close companions.

Time is the variable that all strong correlations have in common. Given enough shared years, any two upward trends will look inseparable — because mathematically, they are.