37 year payoff is 'barely' not worth it? When the panel efficiency starts drooping somewhat at the 20 - 25 year mark?
A 250 Watt panel doesn't stay at 250 Watts - it drops over time.
It would also be an extremely poor investment.
40 year investment = $16.02 return.
A crappy 1% interest savings account for the same $200 over 40 years = $98 profit.
For something to be a smart investment, it has to pay better than a crappy virtually risk free savings account.
Hell in 10 or 15 years politicians might wake up and decide Nuclear was actually the right solution and then you'd lose money!