Generator Costs and Solar Payback in Nigeria — A Worked Comparison
Separate initial simple payback from battery-replacement-aware break-even, with an explicit cash-flow timeline and scenario assumptions.
Updated 2026-09-28
A useful comparison starts with costs you can support: measured generator fuel consumption, actual runtime, maintenance records and a complete solar quote. A calculator scenario is not a survey of Nigerian households or a guarantee of equipment performance.
Generator running cost
The generator calculator uses:
`` fuel cost = litres per hour × operating hours × price per litre maintenance = operating hours × maintenance allowance per hour ``
For illustration only, 1.5 litres/hour × 6 hours/day × 30.44 days is 273.96 litres. At an assumed ₦1,300/litre, fuel is ₦356,148 per model month. At an assumed ₦150 maintenance allowance per running hour, add ₦27,396. These are input assumptions, not current official national prices or typical consumption rates. Replace them with your own measurements and records.
Compare the same service
Generator kVA ratings do not establish fuel use per delivered kWh. Load, efficiency and runtime matter. A solar quote must serve the load and autonomy you need. If you will still use grid electricity or generator backup, that continuing spending is not an avoided cost.
The solar comparison compares a complete new solar system with the running costs of a generator already owned. It excludes buying/replacing that generator. It assumes the entered generator spending is completely avoided after solar installation. It is not a complete ownership-cost or financing model.
Three separate questions
- Initial simple payback: initial system price divided by positive annual operating saving. This excludes future battery replacements.
- Replacement-aware break-even: the point after which cumulative savings remain non-negative through the selected horizon, accounting for timed battery payments. Earlier savings can be erased by a later replacement.
- Total costs over the horizon: cumulative generator running costs versus solar purchase, battery replacements and solar maintenance.
The first battery must already be included in the initial system price. The replacement-price input is used only for future purchases.
Battery timing convention
Replacements occur strictly before the endpoint. With an assumed five-year battery life:
| Comparison horizon | Replacement dates | Count |
|---|---|---|
| 5 years | None before endpoint | 0 |
| 6 years | Year 5 | 1 |
| 10 years | Year 5 | 1 |
| 11 years | Years 5 and 10 | 2 |
A battery payment exactly at the final instant is excluded because no subsequent operation is modelled. This convention does not mean the battery lasts beyond its assumed life.
Worked scenario
Assume generator spending of ₦200,000/month, an installed solar price of ₦4m including the initial battery, replacement batteries at ₦2m each every five years, annual solar maintenance of ₦120,000, and a ten-year horizon.
- Annual avoided generator spending: ₦2.4m.
- Annual operating saving after solar maintenance: ₦2.28m.
- Initial simple payback: ₦4m ÷ ₦2.28m = approximately 1.75 years, displayed as 1.8 years.
- At year 5, before replacement, cumulative savings are ₦7.4m; after the ₦2m replacement they are ₦5.4m. The replacement does not erase break-even in this scenario.
- Replacement-aware break-even maintained to year 10: approximately 1.75 years.
- Ten-year generator cost: ₦24m.
- Ten-year solar cost: ₦4m + ₦2m + ₦1.2m = ₦7.2m.
- Ten-year modelled saving: ₦16.8m.
Halving generator spending to ₦100,000/month changes annual operating saving to ₦1.08m. Simple payback becomes about 3.70 years; the year-5 replacement temporarily takes cumulative savings negative, so maintained break-even moves to about 5.56 years. That is why the two measures should not be conflated.
Boundaries and sensitivity
The calculator holds operating and replacement costs constant, spreads operating costs uniformly through time, and does not discount cash flows. It omits financing, inflation, residual values, inverter/panel replacements, degradation and outages. Those omissions matter; undiscounted savings are not an investment return or an NPV.
Test several equipment prices, replacement intervals and avoided-spending levels. No universal “four hours a day” threshold can establish whether solar is worth buying. Use the sizing tool as a planning aid and have an installer check surge loads, wiring, safety and site conditions.
Correction — 28 September 2026
The former model undercounted battery replacements for horizons such as six or eleven years with a five-year battery. It also labelled horizon-dependent capital divided by annual savings as payback, producing 2.6 years in the default example. The repaired model separates initial simple payback, timed break-even and total horizon costs. Recalculate earlier results, especially non-multiple horizons.