Diesel Generator vs Solar Cost Calculator

What diesel electricity really costs

A generator’s sticker price hides its true cost: the electricity it makes. A small genset burning 0.35 litres per kWh at Rs 290/litre produces power at roughly Rs 100–120 per unit once oil changes and servicing are added — five to eight times a typical grid tariff, and far above what a solar-plus-battery system delivers over its life. The same arithmetic holds in India (₹90+/kWh at ₹95/litre diesel), Nigeria and South Africa. Fuel is the meter that never stops running.

Why partial load makes it worse

Gensets are least efficient exactly how homes use them — lightly loaded. A 5 kVA machine carrying a 1.5 kW evening load can burn closer to 0.45 L/kWh than the 0.3 its brochure implies, and hours of idling for a fridge and a few lights are mostly wasted fuel. Solar with a battery inverts this: capital is spent once and the marginal unit is free, which is why payback against diesel is often 2–4 years where outages are long.

The honest comparison

Solar’s catch is the up-front cost and the battery needed for evening outages — that is why this tool sizes a hybrid system to cover the same energy the genset supplies, not a token array. Where load-shedding runs 4+ hours daily, the diesel line item is so large that even a generously priced hybrid wins within a few years; where the genset only runs occasionally, keeping it as rare backup and using solar for daily savings (see the generator vs battery tool) may be the smarter split. Size the battery portion with the battery bank calculator and the array with the off-grid calculator.

Beyond money

Every litre of diesel burned emits about 2.7 kg of CO₂ plus local fumes and noise; a year of 4-hour daily running on a 3 kW load is roughly four tonnes of CO₂. The carbon offset calculator translates the switch into trees and car-kilometres if you want the full picture.

Frequently asked questions

Typically 3–8× the grid tariff: fuel burn of 0.3–0.45 L/kWh times your diesel price, plus ~15% for oil and servicing. At Rs 290/litre and 0.35 L/kWh that is over Rs 115/kWh; at ₹95/litre it is ₹38+/kWh fuel alone.

Where gensets run daily (load-shedding markets), commonly 2–4 years — the avoided fuel spend is enormous. If the generator only runs a few hours a month, payback stretches and solar should be justified on bill savings instead.

Many keep it as deep backup for long grid failures or monsoon weeks — but it runs a fraction of the hours, so fuel and servicing collapse. A right-sized battery covers routine outages; the genset becomes insurance.

To keep the comparison honest. A small array that cannot cover the outage hours does not actually replace the genset. Matching daily energy (with a hybrid derate for battery losses) compares like with like.