Capper & Co has become the latest Spar member to test the impact of installing doors on its in-store dairy chiller cabinets.

If the trial at Cefn Glas, Bridgend, is successful, the doors could be installed in further company stores.

Installing doors in just one store would save 36 tonnes of carbon a year, the equivalent to the electricity used by 14 average UK households, said ­energy manager Ben Rouncefield-Swales. Each door has a sticker that reads: "These doors are saving more energy than 14 houses use in one year."

Forty Spar independents serviced by James Hall added doors to dairy chillers last year and the wholesaler is rolling them out to its 90 stores by April 2012. James Hall's trial store saw its daily energy use drop by two thirds and add £3,000 to its bottom line. Spar retailer Jonathan James has also added doors to chillers in Ely and Littleport.

Capper & Co has also ­introduced LED lights in open chiller cabinets at its Abertawe petrol station. It expects the upgrade to have paid for itself within two years and save 1.4 tonnes of carbon each year.

AF Blakemore completed its takeover of Capper & Co last month. Capper will trade as a separate division of Blakemore, but a single management team will be responsible for company-owned stores.