Your electricity bill already tells us most of what we need. The rest is arithmetic — and we show it.
From bill to kilowatt-hours
Divide the monthly bill by your tariff per kWh to get monthly consumption, then by thirty for a daily figure. A bill of TZS 180,000 at TZS 350 per kWh is about 514 kWh a month, or 17 kWh a day.
From kilowatt-hours to panels
One kilowatt-peak of panels yields roughly 3.75 kWh a day here (five peak-sun-hours at 75% system efficiency). Seventeen kWh a day therefore needs about 4.6 kWp, which we round up to 5 kWp — twelve 450-watt panels.