Getting the temperature balance right can be tricky, and expensive.

Over the past few years convenience stores have got decidedly cooler as owners have heeded advice to chill most of their drinks and their fresh produce. The result has been big investment and more and more refrigeration in the same size of store. This amount of machinery either makes the store too hot or, if you install up-to-the-minute remote refrigeration, has customers reaching for their overcoats and not inclined to linger for long in the frigid aisles.

So here's a good energy-saving tip from Jonathan James, who is about to put doors back on the chillers in two of his sites an established business at Ely and a new build at Littleport, both in Cambridgeshire.

"I asked my refrigeration company to tell me the difference over 12 months and they did the figures," he says. "With open deck chillers the running costs were £13,577 per annum and for closed doors it was £5,393."

These staggeringly different figures are for all the chillers in a 1,600 sq ft store.

"It's a massive saving," he adds. "I think retailers will question the potential lack of sales from the impulse purchase due to the door acting as a 'barrier', but I believe this will be counteracted by people spending longer browsing the chilled offer due to being in a warmer environment.

"They really are quite 'chilling' sums of money, though," he concludes.