Affordable is what?for whom? Solar heating(including hot water to heat a home..etc)is still in it's developmental stages,even though it has been in study for the past 40 year or so.The big money makers don't want competition for their nuclear power plants,or the old coal burners,,they would rather squash this information rather than give up all that profit making.(same as the auto makers and hydro powered cars..etc) I have been a study of alternate power for many years.I am not the 'professional pessimist' I used to be. I have looked into solar,hydro electric,wind power..etc The best solution would be to build into a hill,the deeper the better,the earth has a pretty constant temp,to cool down or heat up a home isn't like the needs of the average home above ground. As most homes are built above,the need for a better solution is common and would behoove the owners to look for alternates to supply their individual needs,,solar is a good way,,,wind is even easier,but both have their drawbacks. Solar would require what?The sun to be around when need is highest,it won't be there that often,so back-ups are necessary to keep the heat and power needs met. Wind could be used,but the drawback is,what if you don't live where the wind is common enough to turn the wind machine.The additional power can be stored,or sold(a lot don't know that if you produce your own power,and have surplus,the power companies HAVE TO BUY THAT SURPLUS AT THEIR PREMIUM RATE.this is Federal law,energy dept,guidelines,established,IDK,but I know it is a law. Solar would be little use to,say,those living in Washington state,where they have little sun during the year,they have more rainy days,or cloud cover than any other city.They could use wind driven turbines though. Affordability is always an issue. You can make your own solar panels,you can't make a turbine for the same effort or expense. More as I think of it. Ken

IF the "average homeowner" finds himself with enough disposable income to waste on buying electricity at 9-15 times what it would cost via nuclear of coal generation, then solar would be "affordable" -- but always financially wasteful.