As nations face the need to decarbonise their energy supply, there is a risk that attention will be focused solely on carbon and climate change, potentially at the expense of other environmental impacts. To explore the trade-offs between climate change mitigation and other environmental impacts, this work focuses on electricity and considers a number of scenarios up to 2070 in a UK context with different carbon reduction targets and electricity demand to estimate the related life cycle environmental impacts. In total, 16 scenarios are discussed, incorporating fossil-fuel technologies with and without carbon capture and storage, nuclear power and a range of renewable options. A freely available model–Electricity Technologies Life Cycle Assessment (ETLCA)–developed by the authors has been used for these purposes. The results suggest that decarbonisation of electricity supply to meet carbon targets would lead to a reduction in the majority of the life cycle impacts by 2070. The exceptions to this are depletion of elements which would increase by 4–145 times and health impacts from radiation which would increase two- to four-fold if nuclear power were used. Ozone layer depletion would also go up in the short-term by between 2.5–3.7 times. If energy demand continued to grow, three other impacts would also increase while trying to meet the carbon targets: human toxicity (two times), photochemical smog (12%) and terrestrial eco-toxicity (2.3 times). These findings demonstrate the importance of considering a broader range of environmental impacts alongside climate change to avoid decarbonising the economy at the expense of other environmental impacts.