Britain’s energy system operator is pulling the plug on hundreds of electricity generation projects to clear a huge backlog that is stopping “shovel-ready” schemes from connecting to the power grid.

Developers will be told on Monday whether their plans will be dismissed by the National Energy System Operator (Neso) – or whether they will be prioritised to connect by either the end of the decade or 2035.

More than half of the energy projects in the queue will be removed to make way for about £40bn-worth of schemes considered the most likely to help meet the government’s goal to build a virtually zero-carbon power system by 2030.

The milestone marks the end of a two-year process to clear the gridlock of laggard “zombie” projects awaiting connection that meant many workable proposals were facing a 15-year wait to plug into Britain’s transmission lines.

Ed Miliband, the energy secretary, said: “We inherited a broken system where zombie projects were allowed to hold up grid connections for viable projects that will bring investment, jobs and economic growth.”

He added: “To fix this we embarked on ambitious, once-in-a-generation reforms to clean up the queue and prioritise the projects that are ready to help us deliver clean power by 2030.”

Under the previous first-come, first-served model the queue had grown tenfold in five years to about 700GW of generation and storage projects, or roughly four times what the country is expected to need by the end of the decade.

The surge in applications was largely fuelled by a boom in solar and battery projects eager to help the UK meet its green energy targets. Many joined the queue without having the right planning permissions or financing in place to move the project forward, leaving “shovel-ready” projects stuck in the backlog.

Almost twice as many battery projects were rejected from the queue as were fast-tracked by the system operator, according to Neso’s figures, which do not include projects that had already voluntarily left the queue.

Chris Stark, the head of the government’s 2030 clean power taskforce, said: “Queueing is a very British tradition, but the queue to connect to Britain’s grid has held back our economy.

“This overhaul of the connections process is the single-most important step we will take towards a clean power system. The energy projects our country needs now have the green light to deploy at a pace we haven’t seen for decades. This unlocks the modern, clean energy system Britain needs for 2030 and beyond.”

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The queue will be replaced by a delivery pipeline of about 283GW in energy generation and storage projects which can prove that they are “shovel-ready”; some will be fast-tracked for a connection before 2030 while the rest will aim for a 2035 connection.

Almost half of the capacity earmarked for 2030 will be solar and battery projects, according to Neso, while a third of the new capacity will be onshore and offshore windfarms. Only 3% of the capacity due to connect by 2030 will be gas-fired power, it said.

The system operator has also reserved capacity for projects including datacentres and other energy-hungry schemes to connect to the grid. However, these projects face fewer requirements to prove that they will move ahead.

Separately, Monday marks 25 years of wind power generation in the UK since the first turbines were erected at Blyth off the coast of Northumberland. Britain’s 47 operational offshore windfarms now supply nearly a fifth (17%) of its electricity generation – making it the second-biggest power source after gas – with the sector employing about 40,000 people, according to an analysis released on Monday by green group Ember.