Evidence shows the solar panels are important: He doubled the number of solar panels in November after the initial panels weren't enough to power the RPi in the winter. http://pi.qcontinuum.com/failure2.html (The graph also shows the voltage dip below 10V in Nov, probably representing that failure, though it's hard to see the details in the "last year" graph.)

Maybe they could be pointed towards the sun more efficiently, or been a more expensive & efficient model - but the story says why he chose his porch and cheap solar panels.