Yes, but you can't keep an 18% increase going for 20 years (unless inflation rates are anywhere close to it). An electricity bill of R1,000,000 in year 20 is irrealistic unless inflation is also well above 10% for most of the time. In which case you should work out the savings in REAL terms, not...
Although your analysis appears to have some surface validity, it actually doesn't work out in practice/on the ground for South Africa. Let me give you a real example (my current situation): I have just installed an off-grid solar installation (indeed City of Cape Town wants me to install a...
I'm on Telkom's 4Mbps home package. This was during a loadshedding. Sometimes there's very slow connection but mostly it's fine. Streaming Netflix on bigscreen has never been a problem; Showmax usually gives bandwidth problems (very low-res video) but that's probably the Showmax servers.