A 50kW rooftop solar installation is the “most attractive” renewable energy investment according to property consultancy Carter Jones’ 2015 Energy Index.

The company analysed onshore renewable energy installations including wind, solar PV, biomass, hydroelectric, anaerobic digestion and ground-source heat pumps. The index takes into account development costs, value, planning and development timescales as well as the internal rate of return (IRR) and places the technologies against each other to compare their respective benefits against risk.

The analysis found that a 50kW rooftop solar system provided the most lucrative benefit versus risk amongst all the technologies, scoring well in most categories despite offering a lower IRR than a 500kW wind turbine and a 1MW waste anaerobic digestion installation.

The perceived benefits of the rooftop installation contrast almost directly with that of a 5MW ground-mounted solar farm, which has slipped to become only the eighth most attractive green tech investment following the government’s recent proposals to curtail Renewable Obligation (RO) support a year earlier than planned.

Despite the apparent benefits of commercial rooftop solar installations, their uptake in the UK has underwhelmed and yet to reach its undoubted potential. The inclusion of sub-5MW rooftops in the government’s RO cuts is only likely to negatively impact further deployment.

Andrew Watkin, head of energy and marine at Carter Jonas, said the Department for Energy and Climate Change’s recent proposals had presented a “significant blow” to the UK’s renewable industry, particularly given current estimations that solar PV could be subsidy-free in the UK by the turn of the decade.

“As an investment, renewable projects are generally not mature enough to withstand a complete removal of any support mechanism,” Watkin said. He added that “several critical changes” would need to be made, such as reduced costs of installation and grid connection, and an increase in the value of electricity, would need to occur if renewable energy was to succeed without subsidy support.

“Overall, the industry needs support from the Government, not opposition with continual regulatory, planning and financial barriers driving investment away from the sector,” Watkin said.