California, Hawaii, Nevada, New Mexico and Colorado lead the US as the country's top five solar states, according to consultancy Ernst & Young's biannual renewable energy attractiveness indices.

California, the leader last year, came out top again with 1,033MW installed this year – the first state to install more than 1,000MW a year.

The rankings are based on a score out of 100 covering criteria such as a state’s potential for certain technologies, infrastructure and policies.

Splitting ranks by installation type, California is still top in the residential segment but comes and second in utility-scale installations, behind Arizona - though the US Solar Energy Industry Association predicts it will overtake Arizona in this segment this year.

Hawaii and Nevada swapped places in this year's rankings, with Colorado making the top five for the first time

Purely in terms of annual installations, California still ranked as the top state in 2012, followed by Arizona, New Jersey, Nevada and North Carolina. The top five for cumulative solar installed in 2012 were California, Arizona, New Jersey, Nevada and Colorado.

Utility-scale installations totalled 1,781MW in 2012 with 10.5GW in the pipeline according to power purchase agreements – 3.1GW of which is already under construction. The report also predicts that utility procurement will slow down, as utilities reach and exceed purchased renewable energy obligations.

Renting rooftop solar systems has taken off and is expected to continue to be popular, making up 50% of the US solar market in 2012, with system prices dropping 20% between the fourth quarter 2011 and 2012.  

Last year the US installed 3,313MW of solar, with 1,300 installed in the final quarter of 2012 alone. The total of installed solar in the US is now 7,221MW – or more than 300,000 installations. The US also made up 11% of global PV installations.

“While overall US investment in clean energy is down, it’s still ahead of annual investment from prior years,” said Michael Bernier, senior manager, national tax at Ernst & Young.

“What’s important to note is that the US$44.2 billion invested is not representative of the industry’s true expansion. Solar technology, for example, is increasingly cost effective. As prices fall, the initial investment goes a lot further. US$1 billion installs a lot more solar than it did five years ago.”

Despite fluctuating costs, by dollar value the renewables market as a whole grew by 34% in 2012, making up nearly 50% of all new energy generation in 2012.