The HM Revenue & Customs website specifies all VAT rates on the page: Rates of VAT on different goods and services (Power, utilities, energy, heating and insulation) and the relevant notice is VAT Notice 701/19. It also specifies that "fuel for business use is usually standard-rated".
It is also worth noting that energy-saving materials are also charged at the unchanged VAT rate of 5%. This includes central heating, wood-fuelled boilers, micro-CHP, draught-proofing, insulation and renewable-energy generation systems.
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