Amortize the cost of the solar into the electricity used, subtracting the subsidies?
Solar costs rise to the consumer because of subsidies, like everything else the government "helps" with (like tuition costs rising to take in all the government money for college). So if you ask me to run my numbers without the solar tax credit, do I get to adjust the costs I paid up front accordingly to what they would have been without the tax credit?
If you want real world numbers broken down by costs, here's https://freerepublic.com/focus/news/4127577/posts?page=51#51. It's half a year old. To date, my cash flow is in the positive about $2,600 (I would have paid $2,600 more in energy costs without solar and an EV than I've paid out of pocket to set up solar and EV, etc.).
This is not for everybody. One should do his homework to make sure it works well in his area (and do his homework before dissing the idea). But if you take ownership of your energy costs it's quit liberating to have one less thing the Dims control over your finances.