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Free Tool · Solar vs Diesel

DG vs Solar Calculator

DG vs Solar Calculator — quick estimate

Diesel generation costs far more per unit than grid power, which is why displacing DG hours is usually the strongest solar case a factory has. Enter what your DG actually burns and see the cost per unit both ways.

Your diesel generator

20,000 kWh
₹95/litre
3.2 kWh/litre
250 kW
₹80/hour
60%
₹45,000/kW

Solar cannot replace a DG set — it displaces the daytime hours a DG runs to carry load, not its standby role. Set the displaceable share to match when your DG actually runs.

Diesel cost per unit
Solar cost per unit
Diesel burned / yr
Diesel spend / yr
DG maintenance / yr
Units solar would take over
Solar size needed
Solar project cost
Annual saving
Payback
CO₂ avoided / yr
What this means
Cost per unit, diesel vs solar
Solar cost per unit is the project cost plus 25 years of O&M divided by 25 years of generation — an average, not a discounted LCOE, so it ignores the cost of capital. Diesel cost per unit rises every time the diesel price does; the solar figure is fixed the day you buy the plant.

Get a diesel-displacement study for your plant

Our engineers will read your DG log and load profile, work out exactly which hours solar can take over, and size the plant against them. Your estimate above is attached automatically.

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Indicative estimates only, not a binding quotation. Actual DG efficiency varies with load factor and age; actual solar output varies by site, shading and season.

Questions engineers and CFOs ask

Can solar replace my diesel generator?

No, and any vendor who says otherwise is overselling. Solar generates only in daylight and only in proportion to irradiation, so it cannot hold your standby role during an outage at night or in monsoon. What it can do is displace the daytime hours your DG currently runs to carry load, which is usually where most of the diesel goes. Keep the DG for standby; use solar to stop burning diesel for routine daytime running.

Why is diesel generation so much more expensive than grid power?

A DG set typically delivers around 3 to 3.5 units per litre. At current diesel prices that puts fuel alone well above most C&I grid tariffs before you add maintenance, oil changes and overhauls. Because the fuel cost is the dominant term and it tracks the diesel price, DG cost per unit also rises with no cap.

What share of my DG output can solar realistically displace?

It depends entirely on when the DG runs. If it carries daytime process load during grid outages or load shedding, a large share is displaceable. If it only runs at night or as pure standby, very little is. The displaceable share is an input here rather than an assumption, because getting it wrong is the single biggest error in a DG-versus-solar case.

Does this include the cost of a battery?

No. The comparison here is solar against diesel for daytime running, with no storage. Adding batteries to cover evening or outage load changes the economics substantially and needs a separate design exercise around your actual load profile.

Need an exact BOQ, rate analysis or measurement sheet?

This is a quick engineering estimate. For tendering, billing or audit, our QS & estimation team prepares an item-wise BOQ, rate analysis and a verified measurement sheet to IS / CPWD norms — backed by 15+ years and ISO 9001:2015 quality processes.

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