Costs of Photovoltaics Against Other Power Sources

You should look not just at the initial cost, but also at the costs of running the power source for the whole intended lifetime of the equipment (10 years, 20 years, etc).

Points to consider:

• Photovoltaics’ running costs are more or less zero, at least until you have to trade in a battery.
• Grid extension can also have a high initial cost, depending on how far a line has to be extended, and how many users can share this cost. Don't forget the costs of transformers and safety equipment too. The running costs here are low, but not zero.
• A diesel generator can be quite a low initial cost, but running costs can be high, especially if fuel and regular maintenance are needed at a very remote site. And like all engines, it can need special replacement parts that can be very expensive (or impossible) to supply at short notice.
• Primary batteries have an extremely high running cost (the electricity costs around 100x times that of mains electricity) and the cost of sending someone out to replace batteries in a remote area can be high too. Don't forget the cost of disposing of used batteries responsibly too. And if a primary battery runs out before someone has come to replace it, the equipment stops functioning, and that costs money too.
• Gas bottles in TEG systems need regular replacement, so running costs for remote areas can be very high. The burners in TEG systems often need periodic cleaning, which adds to running costs in remote areas.