Cleantechnica.com reports how the study found that analysts were working on costings from 2009, when there's been a huge drop (as much as 70%) in installation prices.
Also, they're working on lifetime spans of 20 years for panels when many newer installations are expected to achieve a working life of 30 years.
Previous costings have also factored a 1% drop in solar panel efficiency per year, when the figure for today's modern units is more like between 0.1% and 0.2% drop in efficiency.
And all this is before you start considering the recent energy price rises.
photo credit: mikael altemark