Generator vs Solar: Which Actually Costs Less?
Compare a quoted solar system against the running costs of a generator you already own. The initial solar price includes the first battery bank. Future battery replacements occur before, but not exactly at, the end of the comparison. Simple payback excludes replacements; the separate break-even calculation follows their timing.
1.8 years
modelled saving over the selected period: ₦16,800,000
Solar has lower modelled costs by ₦16,800,000 over 10 years. This assumes solar replaces the entered generator spending completely. Simple payback excludes future battery replacements; use the break-even and cash-flow rows for those.
| Year | Event | Battery payment | Generator cumulative | Solar cumulative | Cumulative saving |
|---|---|---|---|---|---|
| 0.0 | Initial system (first battery included) | ₦0 | ₦0 | ₦4,000,000 | -₦4,000,000 |
| 5.0 | Battery replacement | ₦2,000,000 | ₦12,000,000 | ₦6,600,000 | ₦5,400,000 |
| 10.0 | End of comparison (no endpoint replacement) | ₦0 | ₦24,000,000 | ₦7,200,000 | ₦16,800,000 |
Works without JavaScript — the figures above are a worked example using the default values.
Before you rely on this
- This is an undiscounted scenario, not a quote, forecast or complete ownership-cost model. It assumes solar delivers the required service and eliminates the entered generator spend. Continuing grid/fuel costs must be assessed separately.
- The generator is already owned: its purchase/replacement cost is excluded. Solar financing, inverter/panel replacements, residual value, degradation, downtime, fuel escalation and inflation are not modelled. Test several assumptions.
- Simple payback = initial system price ÷ positive annual operating saving. Replacement-aware break-even follows the timed battery payments and must remain non-negative through the chosen horizon. Neither is a guaranteed return.
- A replacement exactly at the horizon endpoint is excluded: a five-year battery has zero replacements through year 5, one through year 6 or 10, and two through year 11. A dash means no applicable payback/break-even under that definition.
How this is calculated: Deterministic undiscounted scenario using user inputs. Running costs accrue uniformly; future battery purchases are timed strictly before the endpoint. Shared arithmetic has regression and browser tests. · Data as of 2026-09-28
Reviewed 28 September 2026. Defaults are explicit examples, not guaranteed payroll results, equipment performance or observed household costs. See the linked guide for sources, scope and the correction log.
Worked examples, sources and correction log