Loans for non-trivially profitable investments don't require government interest subsidies.

... for purchases from "approved" "accredited" suppliers[]. AKA the interest differential is regressive tax to funnel money to favored suppliers. Notice there's no option for the poor to simply install it themselves, which would save them more money than an interest free loan, but wouldn't funnel money to rich government approved install contractors.

And there's your grift. As soon as the home owner wants to allocate the "profit" of install to themselves, it is a swift kick in the ass but that will go to our buddies, and thank you very much for your taxes.

[] https://www.energy.nsw.gov.au/households/grants-rebates/home...