In relation to your question the cost of installing a solar panel,in Nigeria is very expensive,but there is this inverter i use and install,which gives me electricity without the solar panel,it charges and stores light when there is power supply and then supplies power,when NEPA/PHCN strikes.
In relation to your question the main reason is cost, Solar power in Africat relys mainly on aid. A system to power a 4 person household can cost around $15,000 USD. Have a look at the Perth solar web page http://www.bledisloeenergy.com.au their systems are top of the line however to power a 4 person house hold it would cost around $20,000 USD. Like Nigeria Perth has harsh sunlight wich degrades a solar panel over time. A $15k system may last 7 years in these conditions but a $20k german system will last 25+ years.
Hope this helps,
The Perth Solar team at Bledisloe Energy
Inferior solar projects executed for some state government have really brought blemish to the growth of green energy solution in Nigeria. Ekiti state would run at the mention of green energy all because huge amount was expended by past government with no positive result. If you need any info regarding saving electricity using solar energy, visit http://www.sunhomepower.com/
Other people asked questions on various topics, and are still waiting for answer. Would be great if you can take a sec and answer them