Global climate change impacts the poor the harshest. They're the least able to cope with it, and can least afford the long-term impact economically and to their food supply.
The subsidies to solar assist in building out the long-term technology/energy innovation and infrastructure necessary to combat climate change. Those investments must be made, because we're not going to just magically wake up one day with extremely effective solar, we have to build our way there gradually through university science, commercial R&D and product deployment.
I'd argue that the wealthier people buying these panels are paying their fair share of the overall cost when it comes making the energy shift possible, and were even more so in decades past when it was far more expensive and far less efficient. The top 20% pay something around 70% of all income taxes; the bottom ~15% have a negative tax basis; so the wealthy are largely funding the tax credits that they're claiming anyway.
The contribution the poor are making in very slightly higher electricity rates, is their fair share of contribution to the solution of climate change. No different than any other product build out in history, in which the rich subsidize most of the expense of new technology, but poorer consumers also have a role to play as prices come down.
It's also worth noting that in the US at least, the poor often have subsidized utilities. It's the middle class that is actually taking the bulk of the cost hit you're referring to, not the poor.