John Lewis is to turn down the temperature in its department stores and Waitrose supermarkets will dim their lights in an attempt to bring runaway energy bills under control. The staff-owned John Lewis Partnership, which includes Waitrose, said its energy bill is threatening to go nearly £20m over budget. Under the plan, Waitrose shops will operate on “half lighting” for the first two hours of trading from Monday to Friday. The group also hopes to save on energy costs by cutting the temperatures in its buildings. Internal communications seen by the Guardian showed that “without intervention”, the department stores-to-supermarkets group faces “£18m energy cost overspending against our original predictions” for the financial year to the end of January. In an email to staff, bosses said: “Next year’s forecast is equally challenging” and that it is targeting savings of £9m in the next 12 months through changes to environmental settings in stores and offices. “Between now and 30 December 2022, the temperature of our branches, offices and distribution centres will be reduced by 2 degrees and systems switched to eco mode,” the email stated. In Waitrose, the brightness of lights and number of lights switched off will vary between stores. John Lewis is conducting lighting surveys in an effort to “explore further reduction opportunities”. It is also examining other options such as putting “night blinds” on fridges, to trap the cold air inside, and switching off unnecessary equipment and lighting in unoccupied areas. The move comes as businesses across the country closely examine their energy costs amid soaring bills. The Co-op has dimmed lights in 500 stores to save £4,000 per site, while electronics retailer Currys has reduced the brightness of its display TVs and turned off every other ceiling light. Despite intervention from government to support households and companies with energy bills, businesses have still seen significant increases in costs on last year. Shops and distribution centres are particularly power-hungry as they have complex systems of heating and chilling. Asked about the plans, Neil Coleman, operations manager for energy and innovation for the John Lewis Partnership, said: “We’ve an ambitious plan to reduce energy consumption and aim to reach net-zero emissions by 2035. With energy prices rising, we’re accelerating this. “As well as improving sustainability, reducing overheads helps keep prices low for customers. The small changes to lighting and heating are just part of our plan, and will be kept under review to make sure it doesn’t impact customers’ shopping experience.” Waitrose said last month that it plans to install heat pumps in all its supermarkets. It intends to replace gas boilers in its 332 stores before 2035. It already has five such devices installed and plans to put in a further 10 next year. The pumps run by extracting heat from the air outside. The grocery retailer also plans to install “air curtain” devices, which direct streams of air to prevent heat leaving stores and cold entering. John Lewis signed an agreement in 2020 under which much of its power usage has been bought ahead at fixed rates. The partnership is looking to keep costs down after it slumped to a first-half loss of £99m, for which it blamed soaring inflation. It has warned that its annual staff bonus is at risk this year. Its chair, Sharon White, has said that the business needed a “substantial strengthening”, including strong Christmas trading, to “generate sufficient profit to share a partnership bonus with partners”. Separately on Friday, the partnership said it had struck a £500m deal with the investment firm Abrdn to build 1,000 residential rental homes, redeveloping three sites already owned by its Waitrose and eponymous retail store chains.