The thing is that it is so much cheaper per MWh to build a coal...

The thing is that it is so much cheaper per MWh to build a coal plant versus cleaner technologies - so even if new energy investment is skewed towards clean tech it says nothing about the capacity created by each form of electricity generation. The figures probably need to be normalised against the percentage of MW capacity that is being created by each technology.

eg. if 10% of expenditure was on coal power, for 80% of capacity, you get a normalised figure of 8. If 80% of expenditure was on solar for 10% of capacity you get a normalised figure of 8, which is equal to the coal figure.

However, like all technology, the cost per unit drops with time, especially when a lot of money is being thrown at the problem. Just look at the ads for Solar systems on the TV - The price is so much cheaper than it used to be even when you remove the rebate. I wouldn't be surprised to see when the rebate is removed that the price of these systems won't shift by much.