In short. An older diesel generator that must meet tighter emission or operating rules has three broad paths: add an emission control device (RECD), convert it to dual fuel, or replace it. The right one depends on current regulation, engine age and condition, fuel availability, duty and cost. Check the current rules first, because they change.
The three options
| Option | What it does | Typical fit |
|---|---|---|
| RECD retrofit | Adds exhaust after-treatment to cut particulates and other pollutants | Engines in good condition where the rule requires lower emissions |
| Dual-fuel conversion | Substitutes part of the diesel with gas, lowering some emissions and fuel cost | Where gas is available and the engine suits conversion |
| Replacement | New set to current emission standard | Old or worn engines, or when other benefits justify it |
Decision factors
- Regulation: which rules apply to your set, location and duty, and what they require now. Verify with the current official notifications. See GRAP and temporary DG operating restrictions.
- Engine age and condition: retrofits make sense for engines with remaining life.
- Duty: standby sets with few running hours have different economics from prime-power sets.
- Fuel: gas availability, price and supply security for dual fuel.
- Performance: effect on power, response, back pressure, reliability.
- Space and integration: room for devices, exhaust and gas trains.
- Cost and timeline: capital, operating, downtime and approvals.
- Warranty and manufacturer support.
Decision flow
- Confirm the requirement: what must the set meet, by when?
- Assess the engine’s condition and remaining life.
- Check technical feasibility of RECD and dual fuel for the model.
- Estimate lifecycle cost for each option over the intended life.
- Consider risk: approvals, supply of fuel, performance.
- Choose and plan, with testing and documentation.
See RECD vs dual fuel vs replacement and replacement vs retrofit.
Cost comparison framework
For each option list capital cost, installation and downtime cost, operating changes (fuel, consumables, maintenance), expected life gained and residual value. Compare as total cost over the same period. Do not compare capital cost alone.
Worked illustration (qualitative)
A 15-year-old 500 kVA standby set that runs few hours a year faces a requirement. RECD may satisfy it if the set is mechanically sound and the rule applies to it. Dual fuel adds little for a set that rarely runs, since fuel savings are small. Replacement may be justified if the set also needs an overhaul. For a prime-power set running thousands of hours a year, the fuel savings of dual fuel may carry more weight. The answer follows duty and condition, not a general rule.
Decision factors
| Factor | Question |
|---|---|
| Regulation | Is the set subject to emission or noise rules that apply to it now or soon? Confirm current official notifications. |
| Age and condition | Repair cost versus replacement cost |
| Fuel cost and gas availability | Does a dual-fuel retrofit pay back? |
| Run hours | A set that runs rarely seldom justifies expensive upgrades |
| Technical feasibility | Does the engine have an approved retrofit? |
| Downtime | Can the site be without the set during work? |
Options
- Keep and maintain: low run hours, good condition, no regulatory pressure.
- Retrofit emission control or dual fuel: where approved retrofit systems exist and run hours justify it.
- Replace: old, unreliable or non-compliant sets.
Payback illustration (illustrative)
A set that runs 2,000 hours a year at 300 kW burns about 160,000 litres. If dual fuel displaces 40 percent at a saving of INR 20 per litre-equivalent, the annual saving is INR 12.8 lakh. If the retrofit costs INR 25 lakh, payback is about two years. A set that runs 200 hours a year takes 20 years, which does not justify it.
Substitution rates vary and plans should be conservative. Confirm with the retrofit supplier.
See RECD retrofit guide and decarbonisation roadmap and upgrade and replacement planning.
Common mistakes
- Deciding from out-of-date rules.
- Retrofitting an engine near the end of its life.
- Ignoring back-pressure and performance effects.
What to send us
Send the generator model, age, hours, duty and location. Send your application details. See also emissions and transition.
Questions engineers ask
What does RECD stand for?
Retrofit Emission Control Device, an after-treatment system fitted to an existing engine’s exhaust.
Is dual fuel always cheaper to run?
Only where gas is available and cheaper per unit of energy and the set runs enough hours to benefit.
How do I know which rules apply?
Check the latest notifications from the relevant authorities for your location and duty. They change.
Will a retrofit affect warranty?
It can. Check with the manufacturer first.
Regulations change. Verify current requirements with the authorities before deciding.