The tariff will drop from 29.3p per kWh to 8.5p per kWh on Monday and solar plant developers have just the rest of this weekend to complete large projects in order to benefit from higher tariffs.
Statistics released by DECC show that there was a 56% rise to 121.6 megawatts (MW) between March and June and 18 times more capacity than a year previously.
Installed capacity for anaerobic digestion also jumped in the second quarter of this year, nearly trebling to 177 kW
But this is expected to increase rather than fall, as Feed-In Tariffs for this technology, which composts organic matter to produce fertiliser and methane that can be burnt to generate electricity, will rise from August 1, by around 2 pence per kilowatt-hour for plants up to 250kW.
The largest single solar installation to meet the deadline is on the Body Shop's head office site in Watersmead, Sussex.
It consists of 3,840 solar modules over 6,355 sq meters (roughly the size of 24 tennis courts) estimated to generate approximately 900,000 kWh of electricity a year - 25% of the site's energy. It is about equivalent to powering the needs of 250 houses.
The Body Shop says it took just nine weeks to install, cost lb2.8 million and has a payback of 7-8 years with the higher tariff rate.
Paul McGreevy, The Body Shop International Director of Values, said that "while we understand the need to prevent commercial exploitation of the Feed-In Tariffs, we are disappointed that large, self-funded scale installations like The Body Shop's, entirely in keeping with the original intention of the initiative, have now reduced considerably in size, postponed or abandoned due to the increased investment."
Hw said he hoped the government would look at the situation again and extend the current Tariff, "or at least consider different methodologies to assess the installations to make it more viable" in order to help bring down the cost of solar modules.
Two other large projects to meet the deadline are in the sunniest part of the UK: Cornwall.
Lightsource Renewable Energy and Solarcentury have helped to build a 1.4 MW solar plant near Truro on a disused tin mine, the first of many renewable projects planned at the site.
"While it's been disappointing the government has decided not to support the large-scale solar sector going forward, the solar farms developed this summer will play a critical role in the supply of green energy in the UK," said Conor McGuigan, head of planning at Lightsource.
Another 1.35 MW plant nearby, that cost around lb4m, was erected in just six weeks and is expected to attract up to lb1bn to the Cornwall area.
The tariff reduction has not stopped a Cornish charity from yesterday launching a lb20 million fund sourced from local PV installers to help community buildings, academy schools, churches, charities and farmers generate their own renewable energy from roof-mounted PV modules.
Community Energy Plus Solar Communities 2011' was launched at the Cornwall Renewable Energy Show.
The installations will crucially be under 50 kW, so continuing to attract the highest tariff, but unlike other 'rent a roof schemes' will also receive an income from any electricity not used within the building that is exported to the National Grid.
If the maximum 50kW were to be installed, this would mean that building owners could save up to lb7,000 a year on bills by using all of the electricity, or receive up to lb2,400 a year for exporting it all to the National Grid.
Over 300 local organisations are expected to take up the offer before the deadline of the 1st April 2012.
Cornish Social Enterprises like this one are experiencing a boom. The Royal Bank of Scotland's new list of the top 100 fastest growing Social Enterprises in the UK contains several from the region, including ReZolve and the Cornwall Sustainable Tourism Project.
The RBS SE100 Index is produced by the Royal Bank of Scotland and Social Enterprise to build intelligence and monitor performances of social enterprises in the UK.
