Simon Collins / shutterstockImagine a perfect summer weekend day: a cloudless blue sky with a gentle breeze. Solar panels are at full capacity, wind turbines are turning offshore – and many people are out and about, in gardens or parks. Electricity supply is high, but demand is low. Electricity systems must balance supply and demand in real time. In the above scenario, when renewables are producing lots of electricity but there isn’t much demand, energy companies may need to curtail output – disconnecting their turbines or panels from the grid, and essentially wasting clean energy that could have been generated. Hours later, when demand rises, that energy is no longer available. In the UK, wind farms are already being paid to switch off on days when supply outstrips demand. Similar curtailment of renewable generation already happens regularly in places with lots of solar power such as California, Spain or Australia. As renewable energy continues to grow – and in the UK’s case, as cheap plug-in solar panels become available – this could happen a lot more often. For example, April 22 2026 was a sunny day in the UK, with moderate wind. Solar generation reduced the demand for gas-generated electricity to almost zero. Had the wind speed been any higher, there could have been more electricity generation than demand. The limits of supply and storageOne option would be to control the supply to try and match demand. When electricity mostly came from fossil fuels, this was easy enough – power plants would just burn less coal or gas. But you can’t control the weather, and you certainly can’t keep sunlight in a pile of fuel to use later. The electricity it generates is either used, stored or lost. Another option would be to simply store that excess electricity until it’s needed. There are lots of approaches available, ranging from huge battery banks to pumped-storage hydro schemes that store energy by pumping water uphill before generating electricity when needed. Millions of electric car batteries could even become part of the grid.But all these technologies remain expensive and limited in capacity. Not all surplus power can be saved for later.Without other solutions, this mismatch can increase reliance on fossil fuels at times of high demand. The UK’s National Energy System Operator (Neso) recently warned it will need to use “more tools, more often” to keep the grid stable.A simpler solutionA third option is to shift when people use electricity.The use of renewable energy has made balancing the grid depend not just on supply – weather conditions – but on user behaviour. If people consume electricity when renewable energy is available, there would be less need for other sources of energy or for big investments in energy storage. That’s why shifting electricity demand is one of the simplest and cheapest ways to balance the grid. Smart meters are already able to vary electricity prices throughout the day. In our summer weekend scenario, when electricity is cheap and plentiful but demand is minimal, a smart meter might advise you that prices have gone right down – or even turned negative – creating an incentive to heat water, wash clothes or charge electric cars. In effect, households would be paid to absorb excess renewable energy. This would encourage people to install smart meters and change when they use electricity. It should be particularly useful for low-income households. And at the national level such payments can be cheaper overall than investments in energy storage or curtailing wind or solar farms and unleashing them later.Paying people to use electricity may sound odd, but it represents the cost of keeping the system balanced.Amin Al-Habaibeh receives funding from Innovate UK, The British Council, The Royal academy of Engineering, EPSRC, AHRC, The British Academy, Th Royal Society, and the European Commission. He is also a member of The Institution of Engineering and Technology (The IET).