Hopes remain that the commercial rooftop market will grow strongly to make up for the expected sharp decline in solar farm development in the U.K. this year and particularly in 2016. However, FIT degradations built into the U.K.’s current incentive program could provide a break on this promising market.

In a sign of the potential of the U.K. commercial rooftop market, major retailer Marks & Spencer announced this week that it has completed the U.K.’s largest single rooftop PV array, with a 5 MW system on its East Midlands distribution center. The project was presented as a case study at the EcoBuild trade show today.

However despite positive stories such as this one, there are fears the FIT program structure will prevent the commercial rooftop space from reaching its potential

“We really want the commercial rooftop market to take off,” said David Pickup, the Solar Trade Association's (STA) Business Analyst speaking to pv magazine from the EcoBuild show. “Our worry is that under the current tariff system there really is not much room for growth before you encounter serious regressions.”

FITs in the U.K. are tied to installed capacity, with tariffs set to decrease as capacity grows.

“It is assessed per quarter,” Pickup told pv magazine. “After 17.5 MW then the tariff begins to decrease and it is something like at 70 MW when the tariff drops by 28%. That is a significant drop in tariff in a short space of time.”

The 5 MW Marks & Spencer (M&S) array illustrates the potential for solar to supply major businesses committed to sustainability. Marks & Spencer has set a goal of sourcing all of its electricity from renewable sources, including 50% from small-scale systems by 2020. The 5 MW rooftop system at its distribution center employs over 24,000 modules and will supply 25% of the distribution centers electricity needs.

“The completion of this project is hugely exciting for everyone at M&S. It is the first significant step in a number of solar energy initiatives we are planning this year,” said Hugo Adams, property director at Marks & Spencer.

The Minister for Climate Change Amber Rudd added that the array demonstrates the potential of U.K. commercial rooftops as “power stations” and that business can benefit as a result.

“More rooftop solar means more jobs - and will also help deliver the clean, reliable energy supplies that the country needs at the lowest possible cost to consumers,” said Rudd.

While the STA fears that the commercial rooftop segment may be cut short by FIT reductions before it reaches its potential, a review of the FIT regime later this year provides some hope.

“What the STA is hoping is that with the FIT review later this year, this can be resolved and allow the rooftop market to really expand and grow because there certainly is huge potential,” said Pickup. “What the STA is calling for is stability and some more long term thinking in getting towards zero subsidy and allowing for growth.”