The UK will only be able to achieve net zero emissions by 2050 if "immediate action" is taken to overhaul transport, heating, and electricity systems in the UK.

That is the stark assessment offered today by National Grid, as the company becomes the latest influential organisation to warn that reaching net zero emissions will require large swathes of the UK's industrial and commercial energy demand to electrify, at the same time as millions of electric cars and electric heat pumps are deployed across the country.

Such a drastic overhaul of the UK's energy system could push up electricity demand from 348TWh per year today to 491TWh in 2050, significantly above the 422TWh a year National Grid believes will be needed under a 2C warming trajectory. Peak demand could spike at around 115GW in 2050, almost twice today's level, the company added.

This surge in electricity demand would require 20 per cent more electricity generation capacity to be built by 2050, as well as the mass rollout of smart charging and vehicle-to-grid technologies to alleviate periods of peak strain on the grid, National Grid said. Business and industry would also have to adopt more demand response measures, it added, to flexibly manage at least 13GW of capacity load during times of high demand.

At the same time, the UK's heating system would have to change radically. A massive programme of energy efficiency improvements would be required for domestic properties to ensure that remaining heat demand can be almost completely delivered through electric and hydrogen technologies. Installation of hydrogen heating would get underway from 2030 onwards, National Grid predicts, with 13.9 million homes being heated by hydrogen by 2050 - three million more than under a two degrees trajectory.

The eye-opening analysis was released today by National Grid as part of its Future Energy Scenarios paper, which traditionally sets out four prospective visions for a future energy system based on extensive analysis of current energy demand and future projections, as well as potential changes in consumer behaviour and technological advances.

Alongside the four scenarios - titled Consumer Evolution, Community Renewables, Steady Progression, and Two Degrees - this year National Grid unveiled a fifth Net Zero scenario, setting out the "end state" for what a net zero economy could look like in the UK.

"Although these are not firm predictions we've talked to over 600 industry experts to build this insight and it's clear whilst net zero carbon emissions by 2050 is achievable, there are significant changes ahead," said Kayte O'Neill, head of strategy and regulation at National Grid ESO.

"It's our ambition to be able to operate a net zero electricity system by 2025 and the fundamental changes outlined in this report make it more important than ever to take a whole system view to ensure we have a coordinated approach to decarbonizing the whole energy sector," she added.

Across the five scenarios, National Grid envisages mass take up of electric vehicles (EVs), widespread rollout of low-carbon heating in homes, and the ongoing decarbonisation of the electricity sector.

But the level of decarbonisation across the scenarios varies markedly, depending largely on how aggressively the UK acts to cut emissions from heating and industry. In the Steady Progression scenario, which only delivers a 58 per cent cut in emissions by 2050, the number of gas boilers remains almost the same, with only a small amount of hydrogen blended into the natural gas network.

In contrast, under the Two Degrees scenario, which is designed to be compliant with the old UK climate target of an 80 per cent cut in emissions by 2050, hybrid and air source heat pumps are rolled out alongside pure hydrogen heating and zero carbon district heating schemes.

According to National Grid, hitting net zero emissions would require all of the action from the Two Degrees scenario, plus further measures. Bioenergy with carbon capture and storage will be necessary to deliver negative emissions for certain activities, while road transport must be completely decarbonised, with passenger vehicles and heavy duty transport shifting to electric or hydrogen power.

According to O'Neill, the UK must focus now on decarbonising heat and transport in order to hit its climate goals. "Electric vehicles continue to be a catalyst for decarbonizing the system, making it more flexible as well as bringing down costs for consumers too - and whilst gas will still have an important role to play, a clear plan for the decarbonisation of heat is needed," she pointed out.

The outlook arrives just a day after the government's climate watchdog, the CCC, issued a withering verdict on the government's climate strategy and similarly declared new policies must be urgently brought forward to accelerate decarbonisation in housing, heat and transport. As National Grid makes clear, without bold policies the UK could well be heading for a future of incremental clean tech deployment, sluggish emissions reductions, and missed climate targets.

The company is always keen to stress its scenarios are not predictions, but there will be many in the green business community who worry that some of National Grid's less ambitious scenarios currently appear more likely than its sweeping net zero vision.