Will heat pumps cause blackouts?

The pathway to meeting the world’s climate targets is electric: fossil fuel boilers and vehicles will make way for electric alternatives, and heavy industry is preparing to swap gas for low-carbon power.

This will present an unprecedented challenge for electricity grids across developed economies, which were originally built to transmit power generated by a few large power stations to homes and businesses that had lower overall demand.

Heat pumps are expected to have a major impact on how electricity grids run. A spell of cold weather could cause a collective surge in power demand from millions of households.

But are these challenges too great for grid operators, and can households expect power blackouts in exchange for a greener energy system?

The claim

Critics fear that heat pumps could lead to a surge in demand for electricity – particularly during winter cold snaps – that could outstrip the UK’s electricity supplies or overwhelm local power grids to cause blackouts.

These fears have been stoked by organisations including the Stove Industry Association, which represents companies in the wood-burning stove industry. Erica Malkin, the group’s spokesperson, told the Daily Express there were “concerns about the expansion of the energy network” and the “very real potential for power outages”.

“The electrification of heat is a sound argument when it comes to carbon-saving, but when it comes to grid dependency we are nowhere near the targets for what would be needed to entirely electricity heat in this country,” she said.

She told the newspaper that in the event of a blackout, households would not be able to heat their homes and might find it beneficial to have a wood burning stove instead.

The Telegraph columnist Ross Clark argued that the UK was “much closer to blackouts than anyone dares to admit” due to the combination of Britain’s rising reliance on electricity and a power sector that is increasingly dependent on renewable energy sources.

The amount of electricity generated by the UK’s gas and coal power plants fell by 20% last year to its lowest level since 1957. Renewable energy provided the single largest source of power at 42%, although gas power plants still accounted for 31%.

“That could leave us trying to power the country pretty much with intermittent wind and solar energy alone – and this at a time when politicians want millions more of us to be driving electric cars and heating our homes with heat pumps, thus substantially increasing demand,” wrote Clark. “How will we keep the lights on? One struggles to find a satisfactory explanation from the National Grid ESO, which is trusted with this task.”

The science

National Grid ESO (NESO), which balances Britain’s electricity supply and demand, would reject the suggestion that there is no “satisfactory explanation” for how it will keep the lights on in Britain’s green electricity future.

The electricity system operator, which is soon to be spun off from the FTSE 100 company National Grid, produces detailed annual forecasts of Britain’s various potential routes towards its climate goals, as well as studies that analyse the changes expected to the UK’s power supplies and electricity demand.

These reports provide a blueprint that is used by the industry and government officials to prepare the grid for the future.

In one report, the grid operator has modelled a “typical” winter day in the fourth of week of January 2035, which provides a snapshot of how heat pumps will be integrated into the electricity system.

By this time the UK’s annual electricity demand is expected to have doubled due to the rollout of heat pumps and electric vehicles, with the country running a net zero electricity grid in line with the UK’s climate targets.

On this day NESO assumes that renewable energy will be only 40% of the UK’s total generation due to low levels of solar and wind power generation in still, overcast weather. Instead, the UK would meet its power demand by using extra gas and biomass power plants fitted with carbon capture technology, as well as power imports from neighbouring countries via electricity interconnectors, and green hydrogen derived from renewable electricity.

Importantly, the model forecasts an increasingly digital power grid capable of making better use of the UK’s renewable energy sources when they are available. This means that even though the UK’s annual electricity consumption will double overall, the peaks of electricity use will not be twice as high.

For example, homes and businesses can charge their electric vehicles or batteries overnight when power demand is lower, helping to keep the daily power use peak from climbing too high. These same energy stores could even help keep the lights on by releasing electricity back to the grid at times when demand for power reaches a peak.

These dynamics have been closely modelled in plans devised by electricity network operators, the companies tasked with running the smaller regional grids that make up the wider UK power system.

These companies carry out “constant and detailed forecasting based on data, research and engagement”, according to the Electricity Networks Association. “This enables effective network planning for the uptake of heat pumps as well as other low-carbon technologies based on a range of scenarios.”

In one set of plans, Scottish Power, which runs regional networks as well as major transmission lines, has created an artificial intelligence-powered “digital twin” of its electricity networks to simulate how they might change by 2045. One of its key findings is that using heat pumps flexibly could help to reduce their contribution to peak demand by up to 32% by 2045, making it easier to keep the energy grid stable.

UK Power Networks (UKPN), which runs the grids serving London and parts of the south-east of England, is already monitoring real-time data from homes that have electric heating alongside an electric vehicle charger, solar panels or batteries, to understand the impact that heat pumps will have on the grid.

UKPN’s project, which it is running with the Energy Systems Catapult (ESC), will help “improve understanding of the expected impact of heat pumps on the power network as domestic heating is increasingly electrified, and provide tools to manage these changes”, the company said. “This will allow UK Power Networks to ensure they invest in network upgrade and development more efficiently, and so reduce customer bills.”

The caveats

The electricity grid is a dynamic and evolving situation for the system operator.

The forecasts undertaken by NESO were prepared under the UK’s previous government, which aimed to run a net zero electricity grid by 2035. Under the new Labour government this target is expected to come forward to 2030, meaning the rollout of renewables will need to be even faster than the previous target, which was itself considered ambitious by the industry. This may make it trickier to manage the influx of heat pumps by the end of the decade.

The existing targets also suggest a combination of heat pumps alongside hydrogen boilers, although hydrogen boilers are expected by experts to play a more limited role than first envisioned, meaning heat pumps could be required to play a larger role that the NESO is prepared for. The government is due to make a final decision on the role of hydrogen heating in the UK’s net zero future by 2026, but until then forecasts will include hydrogen heating.

The verdict

There is still time for energy grids to evolve before heat pumps have an impact on the UK’s electricity system. It will no doubt be trickier for the grid operators to keep the lights on than it was in the past – but there is no reason to believe that the UK will experience more blackouts in the future as a result of heat pumps if careful modelling and upgrades continue.