Diesel Genset vs Solar Cost Calculator
Compare the per-unit cost of running a diesel generator against a captive solar plant for the same load.
Result
- Diesel cost per unit
- ₹31.00
- Captive solar cost per unit
- ₹1.60
- Diesel units solar can displace
- 78,000kWh/year
- Annual saving
- ₹22,92,986
- Solar payback
- 1.0years
- CO₂ avoided per year
- 62.7tonnes
Estimates only. Nothing you type is stored or sent anywhere — the calculation runs entirely in your browser.
How this works
For commercial and industrial users, diesel gensets are the most expensive electricity on site. A generator consuming 0.3 litres of diesel per kWh at ₹95 per litre is already at ₹28.5 per unit in fuel alone, before maintenance, before the operator, and before the capital cost of the machine. Captive solar, once built, produces at the levelised cost of the asset — typically a small fraction of that.
The catch is coincidence. Solar produces on a fixed daytime curve while a genset runs whenever the grid fails. Solar therefore displaces diesel only for load that occurs during generation hours, unless you add storage. This calculator asks you separately for total genset hours and the share of those hours that fall in daylight, because that share is what actually converts into savings.
Where a site runs gensets primarily for evening or monsoon-night outages, the honest answer is that solar alone will not displace much diesel and the payback stretches out. Where the outages are daytime industrial load shedding, solar frequently pays back inside three to four years at current capital costs.
Common questions
- What diesel consumption should I assume per kWh?
- A well-maintained genset at 75% load typically consumes 0.28–0.32 litres per kWh. Lightly loaded gensets are far worse — running a 500 kVA set at 20% load can push consumption above 0.45 litres per kWh.
- Should I add a battery?
- Only if your outages are concentrated outside generation hours. Batteries add materially to capital cost per usable kWh, so they make sense for night-time critical load rather than for shifting bulk daytime savings.
- Does this account for maintenance?
- Genset maintenance is included as a per-unit adder that you can edit, and solar operations and maintenance is applied as an annual percentage of capital cost.