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The average home really doesn't use that much energy over a month. It spikes with AC and heating use otherwise it is not much more that a couple of kW at any one time.

So let's say you have a roof area of 30’ by 20’. That's 600sf at just 10 watts/sf that would be 6kW. Let's say you can get that for 8 hrs a day, that's 48kWH a day. At 10 cents a kWH lets call it $5 a day, for 30 days a month that is pretty close to what I pay a month in electricity bills in the DC suburbs for 2500sf house.

They are in fact getting pretty close to making this viable. If the solar cell costs get below 50 cents a watt they will be on everyone’s roof. Right now you can buy solar panels close to a dollar a watt.

Roof panels can be a competitive product, but they will always need a supplemental power source - night time, clouds, winter sun angle - unless there is a major breakthrough in battery technology.

Batteries have improved at an even slower pace than solar electric panels.

I read recently that battery storage has increased only by a factor of four since the 1930’s.

I assume the issue with batteries is pretty simple - if you want more electrons, that means more size and more weight.