At St Paul's Cathedral in Melbourne, where most of the 350 lights hang 15 metres above the ground, rising up to neo-Gothic spires and a timber-vaulted ceiling, screwing in a new globe is no small feat.

Over two weeks a team of electricians recently used cranes and scissor lifts to replace every light in the 19th-century cathedral with museum-grade energy efficient globes.

The church says the LED light project, which includes rewiring, new light fittings and a dimmer system that can be controlled remotely with a smartphone, will cut its carbon footprint by almost a third.

The move is also expected to slash the cost of powering the state's most popular religious landmark from $183,000 a year.

Anglican Dean of Melbourne, The Very Reverend Dr Andreas Loewe, said a carbon audit had found the cathedral lights were one of the main sources of electricity use at the site.

The new 14.5-watt bulbs will last up to seven years, reducing energy output and the need for maintenance, he said.

Dr Loewe said the church was committed to becoming carbon neutral and hoped the initiative would inspire other religious buildings to take action to reduce their carbon footprint.

"We do want to model to the rest of the religious community a way in which they too can reduce their carbon emissions," he said. "We believe that churches, offices, landmark buildings and other organisations should really look at this example and get on with it."

Earlier this month, the Pope decried humanity's damaging footprint on the earth and warned of the "fragility of the planet". In his most recent encyclical, Pope Francis issued a call for action on climate change, blasting those who oppose efforts to combat it, and blamed human greed for environmental damage.

Dr Loewe said the Pope's message was "absolutely spot on". "Saving the planet is not a matter of denominations," he said. "Saving the planet is a matter for Christians and all people of good will to come together and say that this is something we believe in and this is something we must prioritise."

The church's $100,000 lighting upgrade was funded equally by parishioners and a sustainable landmarks grant from The Lord Mayor's Charitable Foundation.