They are good enough. Low efficiency just means we have to buy more of them. Obviously we'd need solar plants (and maybe wind parks and other clean sources) to also power those with limited access to roof surface.
Of course, bad weather doesn't mean solar stops working; it just reduces the output. The effect is typically very local as well. So, all that means is that you need a bit extra capacity to cover for that or import energy from somewhere else where the weather isn't miserable.
When (not if) the price for solar and wind drops 10x, you'll be able to buy 10x more than what you need and still beat coal/gas/nuclear on price. 10x is an insane safety margin that would mean you produce more than you need even on the most cold, dark, and miserable day imaginable. And of course solar is not the only source of clean cheap energy. Wind would be another popular option.
Further south in Germany, Netherlands, etc. Solar is usable throughout the year and quite common. Obviously output in the summer is going to be much better than during the winter.
We are well past the point where tracking the sun was desirable. The apparatus that allows solar panels to track the sun is now much more expensive, especially when you consider the maintenance costs, than just using more static panels.
>Not to dismiss it entirely but arguing cost increases seems a bit far fetched in light of current trends in the market.
I think what the parent was saying is that because solar and wind don't reliably produce energy, we will need redundancy. As the market share of solar and wind grows we will need to increase the amount of storage and power generation far beyond what we normally need to operate.
Let's say you have a city that uses 1 GWh of electricity per day. If you were to generate all the electricity with natural gas then you need to have 1 GWh plus some extra for redundancy to fulfill the needs of the city. If you generate 5% with solar and the rest with natural gas then nothing really changes. If the weather is bad then the natural gas plant will step in.
As the share of your solar power generation grows toil need more and more redundant storage and solar power generation. If you rely 100% on solar power generation and the weather can be bad for a week in a row over the city, then you'll need storage that will last for more than that entire week. Not only that, you'll also need extra power generation capability to be able to fill and maintain that storage.
Just to put this into perspective: the US uses about 10 TWh of electricity per day.