Off-grid solar and battery sizing for Dodoma
A 1 kW array in Dodoma produces about 668 kWh a year — but that annual figure is not what sizes a system. September is, and in September the same array makes only 1.3 kWh a day, against 2.7 in June.
What do you need?
Battery bank
12.9 kWh
268 Ah at 48V
Solar array
3.14 kW
about 7 panels of 450W
Summer only
1.50 kW
if you only use it June-ish
Sizing by household
Year-round systems in Dodoma, three days of autonomy, lithium.
| Use | Per day | Battery | Array | Panels |
|---|---|---|---|---|
| Weekend cabin LED lights, phone charging, a laptop, a small water pump |
1.0 kWh | 4.3 kWh | 1.05 kW | 3 |
| Basic off-grid living The above plus a small fridge and a few hours of television |
3.0 kWh | 12.9 kWh | 3.14 kW | 7 |
| Comfortable off-grid home Full-size fridge-freezer, washing machine, pumps, laptops |
6.0 kWh | 25.7 kWh | 6.29 kW | 14 |
| Everything except heating A normal household load, with heating and cooking on gas or wood |
10.0 kWh | 42.9 kWh | 10.48 kW | 24 |
Why September decides everything
Array needed to cover 3.0 kWh a day, month by month. The tallest bar is the one your system has to survive.
| Month | Yield per kW | Array needed | |
|---|---|---|---|
| January | 1.63 kWh/day | 2.50 kW | |
| February | 1.64 kWh/day | 2.48 kW | |
| March | 1.72 kWh/day | 2.37 kW | |
| April | 1.83 kWh/day | 2.23 kW | |
| May | 2.37 kWh/day | 1.72 kW | |
| June | 2.71 kWh/day | 1.50 kW | |
| July | 2.56 kWh/day | 1.59 kW | |
| August | 1.87 kWh/day | 2.18 kW | |
| September (worst) | 1.30 kWh/day | 3.14 kW | |
| October | 1.33 kWh/day | 3.05 kW | |
| November | 1.41 kWh/day | 2.90 kW | |
| December | 1.58 kWh/day | 2.58 kW |
What the numbers assume
- Battery capacity allows for inverter losses, round-trip efficiency, and a usable depth of discharge — 80% for lithium, 50% for lead-acid. Nameplate capacity is always larger than the energy you can actually use.
- Array size includes a 25% margin over the bare requirement. A system that exactly meets demand on an average day of September never recovers from a run of cloudy ones.
- Yield figures are measured, not modelled — PVGIS satellite and reanalysis data for 2005–2023, at the optimal angle for this location, with 14% system losses already deducted.
Other cities in Tanzania
Limitations
- No shading. Trees, terrain and buildings are not modelled and can dominate everything here.
- Nothing about heating. Electric heating or cooking multiplies these figures several times over. Off-grid systems almost always use gas or wood for heat.
- Batteries age. Capacity falls over years; installers commonly oversize to allow for it.
- This is an estimate, not a design. A real installation needs a survey, local electrical regulations, and someone accountable for the result.