Green Energy

https://en.wikipedia.org/wiki/Levelized_cost_of_electricity

calculate total costs of power plant + fuels over the power plant's lifetime, divide by total kWh produced --> that gives you the average cost per kWh.

it is key here to see that even if solar panels produce energy over and over again, they still have a finite lifetime so they only produce a finite amount of energy per panel. so you can still calculate the cost per kWh by dividing panel cost by total kWh produced. the result then is non-zero because total kWh produced is not infinite.