25 years is the duration of the contract; the plant does not become defunct at the end of that period. Projects like this are contracted over fairly long initi

25 years is the duration of the contract; the plant does not become defunct at the end of that period. Projects like this are contracted over fairly long initial periods to cover capital costs and so forth, but not so long that governments are locked into bad deals long-term. At the end of a contract period, a new deal is negotiated to continue operations unless it isn't beneficial to do so. Solar plant operations and maintenance costs are relatively low compared to other kinds of generation, so it's unlikely that the plant will become defunct at the end of the 25 year period. Solar panel performance at the end of a 25 year period will likely be between 90-80% of initial performance. This is well within what is required for useful economic generation. Most likely, a new deal with be made at lower prices because no capex is needed. Panel degradation is relatively constant at ~0.6-1% per year. This means that a well-performing panel would be producing 50% of it's rated output after a century, or 36% with poor performance. These are long-term solutions.