Energy is not sufficient to do stuff. You still need a thing to convert that energy into something useful, and those things cost money as well. Taking refrigeration as an example; using my local home improvement store as an example (which isn't the most representative for the costs applicable to national development, but should be good enough for napkin math):
A refrigerator/freezer running at 1.17 KwH/day goes for about $800 USD. [0]
For $100 USD, I can get a solar panel that claims about 300 Wh/day[1]
This puts the cost of energy at about the same as the cost of making the energy useful. Obviously Rwanda isn't going to buy retail from Home Depot. Further, I suspect that when done at scale, you will find that the discount you see over retail for energy is more significant than the discount you see for refrigerators.
Granted, making the refrigerator requires energy. However, it also requires a factory and components. Making those requires energy, but also other factories and components.
Looking at how this plays out in a developed country. In the US 2021, the electricity industry had a revenue of about $430 Billion [2], for an economy with a GDP of about 23 Trillion [3]. In total, energy accounts for about 5% of GDP. [4]
Running that $800 USD refrigerator I mentions above would cost me about $0.08 USD/day
Sure, doing stuff requires energy, and we need to prepare for the energy demands of developing nations to increase. However, the cost of energy is a small fraction of the cost of most of the stuff you want to do with the energy. Sure, if energy was orders of magnitude cheaper, then that may enable more usages of energy, but even those things would require investment beyond energy generation to do.
You ignored inverter, battery, battery replacement, and installation costs. All that has to be amortized along with the interest rate or opportunity cost of tying up your capital.
There a lot of refrigerators cheaper than $800 and just about all of them cost more to power than to buy.
Good point, so you buy 4 panels for $400 USD. Next what do you need: wiring, mounting, inverter, storage - I'd like to set up a fridge at the camp, any idea the price on everything I would need?
A refrigerator/freezer running at 1.17 KwH/day goes for about $800 USD. [0]
For $100 USD, I can get a solar panel that claims about 300 Wh/day[1]
This puts the cost of energy at about the same as the cost of making the energy useful. Obviously Rwanda isn't going to buy retail from Home Depot. Further, I suspect that when done at scale, you will find that the discount you see over retail for energy is more significant than the discount you see for refrigerators.
Granted, making the refrigerator requires energy. However, it also requires a factory and components. Making those requires energy, but also other factories and components.
Looking at how this plays out in a developed country. In the US 2021, the electricity industry had a revenue of about $430 Billion [2], for an economy with a GDP of about 23 Trillion [3]. In total, energy accounts for about 5% of GDP. [4]
Running that $800 USD refrigerator I mentions above would cost me about $0.08 USD/day
Sure, doing stuff requires energy, and we need to prepare for the energy demands of developing nations to increase. However, the cost of energy is a small fraction of the cost of most of the stuff you want to do with the energy. Sure, if energy was orders of magnitude cheaper, then that may enable more usages of energy, but even those things would require investment beyond energy generation to do.
[0] https://www.homedepot.com/p/Frigidaire-20-5-cu-ft-Top-Freeze...
[1] https://www.homedepot.com/p/Grape-Solar-100-Watt-Monocrystal...
[2] https://www.statista.com/statistics/190548/revenue-of-the-us...
[3] https://www.bea.gov/news/2022/gross-domestic-product-fourth-...
[4] https://www.eia.gov/todayinenergy/detail.php?id=53620