> When I looked into it in my country, the payback time for a solar system was 10+ years, and estate agents were reportedly estimated they added nothing to the value of the house.
Solar panels in this type of deal are debt incurred by the home owner so the cost should be deducted from the sale price. In other words, do not buy a house with mortgaged solar panels.
I think you've misunderstood. GP is talking about time to break-even on purchase, and that despite having purchased outright, the panels being worthless as far as house-valuation metrics went
