So how do you 'invest heavily in alternative energy sources'? If it's putting Treasury money into something like the iShares Global Clean Energy Index Fund (ICLN) then it's an investment - you can calculate an internal rate of return, a mark-to-market value, estimated yield-to-maturity, and other metrics which demonstrate how it actually is an investment.
Compare this to spending on alternative energy sources. There you have a few options. You could fund basic research; if so then it's not an investment because you don't have a shippable product you can calculate revenue (and thus returns against) and thus it's a cost by definition. If you ever did develop a product you could calculate the effective rate of return on your R&D as an integral element of your net profits but otherwise it's still just a cost.
You could have the government spend on actual alternative energy generation capability like solar panels but unless the US Government plans to get into the energy distribution sales business it's not an investment either as that spending won't generate interest, income, or appreciation in value.
Where you may be confused is conflating the idea the government might (theoretically) save money in the long run by incurring current spending in alternative energy capital expenses (the actual purchase of the equipment) which can enable a cost avoidance by the government in future operating costs (the money saved on traditional energy supplies less the operating costs needed to maintain the panels). It's still not an investment by definition but you're at least getting closer.
This again goes back to my point about accuracy, you're attempting to leverage the halo effect and positive connotations of the word "investment" when you actually mean spending that enables policy goals you like. The definition of words don't change though just because you would prefer to use a word you think sounds better to people. It's perfectly fine to pitch benefits to people that are only realized after incurring a cost, don't lie to people and call stuff "investments" when they aren't though.