Is $30,360 to install a 24-panel solar system a fair price?

I got two quotes for solar panels in Okanagan, BC. I'm located in an area where I should get a $5k rebate from Hydro and can get a 0% loan for 10 years. I upgraded my service to 200A with a 225 bus bar to maximize the system size. There's a tree I can't remove that causes shade, impacting the output of the 30-panel option. I'm debating the ROI and payback period, which I calculate to be around 21-22 years with the rebate. I want solar for environmental reasons but also need it to make financial sense. I'm concerned about the system's lifespan relative to the payback period.