The goal is to create demand, which in turn attracts suppliers to the field and ultimately leads to the development of newer and better products and services. It’s not just good for the environment. It’s also healthy for companies’ bottom lines.

Cost in cents (or pence, if you’re in the UK) per unit of electricity produced over the whole life cycle.

You have to take into account discounting too: money spent now is worth more than money spent later, because if you’d invested the money now you would have got more money later from interest. You also have to include the likely cost of fuel in the future, maintenance etc.

The calculations are relatively simple if you just want to work out how long it’ll take for a solar panel to pay back its cost. It’s quite hard, so I’d rely on published work.

So look up ‘electricity costs per kWh by source’ or something like that!