While I do agree that it is a bad time to invest in electricity generation business in general, an electricity consumer would invest in solar today because he has some saved money today, and it's the best ROI around. (Or wouldn't, if it isn't.) The price it may have tomorrow does not change the overall picture.

Couldn't the consumer deduce that the better ROI is to keep the money as cash (or some other liquid investment) for 2-3 years and then spend it on solar in 2 years time? My expectation of future prices definitely affects how I spend my money today.

Yes, there are possibilities for speculating, but you are betting prices will fall faster than inflation + the ROI of your investment.

Plenty of people don't want that kind of risk.

Maybe it's that a dollar today is still worth more than a dollar tomorrow.

With that logic no solar power plants that exist now would ever have been built.

Incentives phase out over the next few years.