While LEDs are becoming established in areas such as highway lighting, he said: "There the calculation is much more straightforward than in horticulture, where applications are more complex and energy use is a smaller part of the story."
LEDs appear to present fewer maintenance issues than high-pressure sodium lights because they come as complete assemblies, but cleaning is still important, he said. Claims that their light depreciation is lower and lifespan longer "are not yet supported by data".
More generally: "Electricity use isn't the be-all and end-all. Selective operation can give running cost savings. Timing electricity use is key, and it's getting more complex. If you buy in electricity, try to do so overnight, not during peak periods of 4-7pm weekdays, November to February."
Meanwhile, those who generate their own electricity via combined heat and power must decide whether there are times when this would be worth more sold than used, he said. "Horticulture will have a role in demand management of energy, which is still in its infancy in the UK as we move from a few, large, dirty generators to ones that are much more scattered around."