Europe's photovoltaic market continued to boom in 2011, with installed capacity doubling across the 27 EU member countries, new research indicates.

EurObserv'ER, an EU-backed renewable energy research group said in a report issued Tuesday that cumulative photovoltaic capacity in the European Union at the end of 2011 was 51.3 gigawatts-peak -- up from 29.8 gigawatts-peak the previous year.

European users hooked up 56 percent more solar capacity in 2011 than they did in 2010, with 21.5 gigawatts-peak coming online during a year that saw installations boom, especially in Italy, Germany and Greece.

France, Belgium, Britain and Slovakia also saw big percentage jumps in installed solar capacity, the EurObserv'ER Photovoltaic Barometer reported.

"Photovoltaic market growth confounded the naysayers once again as the latest installation estimates show worldwide grid-connected photovoltaic capacity of at least 29 gigawatts-peak, compared with 16.8 gigawatts-peak the previous year," the report said.

The European Union led the way, accounting for 74 percent of worldwide connected solar capacity.

Germany and Italy remained the clear leaders with almost 17 gigawatts-peak of new on-grid capacity between them.

Photovoltaic's 2011 growth, at 21.5 gigawatts-peak, also handily beat the growth of other types of generating technologies. Some 9.3 gigawatts of new wind power came online in Europe last year, along with 2.2 gigawatts of coal-fired capacity.

Sparking the huge jumps in Italy and German have been the plunging prices of PV equipment combined with generous subsidies to users in the form of feed-in tariffs.

The rush by businesses and homeowners in those countries to tap the subsidies has been intense thanks to the free-falling prices for the monocrystalline modules used in the photovoltaic arrays. The average price of the units fell from $1.83 per watt in January 2011 to $1.04 a year later, EurObserv'ER said.

Until recently, that had resulted in push back by cash-strapped national governments seeking to cut the solar subsidies while implementing budget austerity programs in response to the European debt crisis.

In the overheated Italian market, the government of Prime Minister Mario Monti is rolling out a series of monthly tariff reductions to small users and is clamping down on the levels of funding paid to big, commercial solar installations.

Under the provisions of Italy's Fourth Conto Energia, distinctions for the first time will be made between self-consumed and for-sale electricity beginning in 2013.

German Chancellor Angela Merkel has also been pushing for a reduction in the solar feed-in tariff as part of the austerity package promoted by her Christian Democrat-led government.

But her efforts were dealt a blow last week when the upper house of the German Parliament, the Bundesrat, voted to send the measure to a parliamentary arbitration committee that can make changes.

That move was followed Sunday by historic electoral losses suffered by Merkel's conservative political coalition in the populous state of North Rhine Westphalia, and by Wednesday's firing of Environment Minister Norbert Roettgen -- who was touted by some as Merkel's possible successor.