Higher spending on the energy system raises the prospect of households and businesses shouldering increased costs through taxes or bills.
Mr Cavada is the latest energy industry figure to express scepticism about Labour’s plans, which the Conservatives have claimed would risk blackouts. Sir Jim Ratcliffe, the petrochemicals billionaire, said on Thursday that Labour’s net zero grid target was “absurd”.
Labour has insisted its plans are deliverable and will ultimately bring energy bills down.
In an interview with The Telegraph, Mr Miliband said he believed the 2030 target was achievable and was a crucial part of the drive to net zero.
The Labour manifesto pledges to retain a strategic reserve of gas power stations “to guarantee security of supply” and says it will partly fund green investments by expanding the windfall tax on oil and gas companies.
Electricity demand is expected to rise from around 300 terawatt hours per year today to about 360 terawatt hours by 2030.
The bulk of Britain’s future supplies are forecast to come from weather-dependent renewables such as wind and solar farms, backed up by batteries and nuclear power, but gas-fired power stations will still be needed at certain times to keep the lights on.
However, instead of seeking to eliminate their emissions completely by 2030, Mr Cavada urged future governments to proceed more gradually by blending hydrogen into their fuel.
Mitsubishi Power believes existing gas turbines could burn gas that is 30pc hydrogen with only minor modifications.
Mr Cavada admitted that supplies of hydrogen were currently small and highly expensive as well, but argued that – as with wind and solar power – costs would fall as production was scaled up.