It can take 30 years to break even. It's attached to a house, which will be around at least that long.
When you sell that house in the future, it's STILL worth $2500 a year off the electricity bill. The house buyer will be willing to pay more for the house for that; if they keep the house for five years, they will have spent $12500 less on electricity, and they'll still have an electric roof to sell to the next buyer. So you should be able to recoup a chunk of that investment when you sell, because a house that can fuel cars using sunlight is worth more than one that can't.
When you sell that house in the future, it's STILL worth $2500 a year off the electricity bill. The house buyer will be willing to pay more for the house for that; if they keep the house for five years, they will have spent $12500 less on electricity, and they'll still have an electric roof to sell to the next buyer. So you should be able to recoup a chunk of that investment when you sell, because a house that can fuel cars using sunlight is worth more than one that can't.