RECD vs. Dual Fuel Kits: Which DG Set Upgrade Is Right for Your Facility?

There’s a conversation that plays out in almost every facility manager’s office at some point: someone brings up the generator, and within a few minutes the discussion splits into two very different directions. One person wants to talk about the black smoke that neighbours have started complaining about. Another wants to talk about how much diesel the unit is burning every month. Both are legitimate concerns, and both point toward a genuine upgrade — but they don’t point toward the same upgrade.

This is the confusion that trips up a lot of facilities when they first start researching DG-set retrofits. Retrofit Emission Control Devices (RECD) and Dual Fuel Conversion Kits both fall under the broad umbrella of “diesel generator upgrades,” they’re both installed on an existing generator rather than requiring replacement, and they’re both frequently mentioned in the same breath by vendors, consultants, and even government advisories. But they are engineered to solve different problems, and treating them as interchangeable is where a lot of retrofit budgets get spent in the wrong direction.

Let’s take them apart properly.

Two Technologies, Two Different Jobs

Think of a diesel generator as having two separate output streams that create two separate concerns: what comes out of the exhaust pipe, and how much fuel goes into the tank. An RECD is built to deal with the first. A dual fuel kit is built to deal with the second. Neither technology was designed to solve the other’s problem, even though a well-run facility often ends up caring about both.

An RECD sits in the exhaust line. It doesn’t touch how the engine burns diesel — it treats what comes out afterward, filtering particulate matter and reducing selected harmful gases before they reach open air. A dual fuel kit, by contrast, works upstream. It changes what goes into combustion in the first place, blending a gaseous fuel — usually CNG, PNG, or biogas — alongside diesel, with a controller managing the ratio in real time.

If you remember nothing else from this article, remember this distinction: RECD treats exhaust. Dual fuel changes fuel input. Everything else follows from that.

Why This Distinction Actually Matters for Your Budget

Facilities sometimes approach a retrofit conversation the way they’d approach buying insurance — as if there’s a single “upgrade package” that covers every possible concern. That’s not how this works, and it’s worth being direct about why.

If your actual pain point is a pollution-control notice, a compliance audit finding, or persistent complaints about smoke and odour near the DG set, a dual fuel kit will not resolve that. It might reduce total diesel burned, which has a secondary effect on total emissions, but it does nothing to treat the particulate matter and harmful gases in what’s still coming out of the exhaust. You’d be spending capital against the wrong problem.

Conversely, if your actual pain point is the size of your diesel bill and the generator runs for genuinely significant hours every month, an RECD won’t move that number. It’s not designed to. It will make your exhaust cleaner — which matters, and which may itself be worth doing — but your fuel cost will look exactly the same the day after installation as it did the day before.

This is why the very first step in any retrofit decision isn’t “which product should I buy” — it’s “which problem am I actually trying to solve.” Get that wrong, and the most sophisticated retrofit hardware in the world won’t help you.

A Closer Look at RECD Technology

An RECD, or Retrofit Emission Control Device, is an after-treatment system fitted into the exhaust path of an existing diesel generator. The core idea is straightforward: instead of requiring a facility to replace an older, otherwise serviceable engine just because it doesn’t meet newer built-in emission standards, an RECD gives that engine a way to catch up — chemically and mechanically treating the exhaust stream before release.

Inside a typical RECD, you’ll generally find a combination of components working together: a Diesel Oxidation Catalyst (DOC) that helps convert carbon monoxide and unburned hydrocarbons into less harmful compounds, and a Diesel Particulate Filter (DPF) that physically traps soot and particulate matter. Sensors and monitoring controls track how the system is performing — exhaust temperature, pressure across the filter, and general operating status — which matters because these systems need periodic regeneration (essentially, burning off accumulated soot) to keep functioning correctly over years of use.

You can read a deeper breakdown of exactly how DPF and DOC components work together on our dedicated page about the Retrofitted Emission Control Device, including the capacity ranges ACEGET’s RECD line covers.

RECD tends to be the right conversation starter when:

• Your facility has received, or is at risk of receiving, a pollution-control notice tied to your DG set
• Smoke, odour, or visible exhaust has become a source of complaints from neighbours, tenants, or occupants
• You want to extend the operational life of an existing generator without replacing it, while addressing its emissions profile
• There’s no commercially viable or physically accessible gas supply at your site, ruling out dual fuel as an option anyway
• Cleaner surrounding air quality near the generator location is itself the objective, independent of fuel cost

A Closer Look at Dual Fuel Technology

A dual fuel conversion kit takes a different approach entirely. Rather than treating exhaust after combustion, it changes the fuel mix going into combustion. The generator continues running on diesel, but a portion of that diesel requirement is substituted with a gaseous fuel — commonly CNG, PNG, or biogas depending on what’s available at your site.

The controller is the brains of the operation here. It continuously monitors engine parameters and adjusts the gas-to-diesel ratio to stay within safe operating limits. Critically, if gas supply drops, pressure becomes unstable, or any safety condition is detected, the system is designed to fall back to diesel-only operation automatically — the generator doesn’t stop running or become unreliable; it simply reverts to the fuel source it was originally built around.

Full details on how this fuel-ratio control and safety-interlock system works are available on our Dual Fuel Solutions page.

Dual fuel tends to be the right conversation starter when:

• Your DG set runs for meaningful, regular hours — not just occasional emergency backup during outages
• There’s a dependable, commercially attractive gas supply at or near your site (piped or via cylinder logistics)
• The primary driver is reducing ongoing diesel spend and improving the generator’s operating economics
• Your facility has the physical space and safety infrastructure to accommodate gas storage or piping
• Reducing overall diesel dependence is part of a broader operational or sustainability objective

When Facilities Actually Need Both

It would be tidy if every facility fell cleanly into one category or the other, but that’s not always true — and pretending otherwise does a disservice to facilities with genuinely layered requirements.

Consider a hospital running a DG set for both scheduled load-shifting hours and emergency backup. It may be located close to patient wards or public-facing areas, which puts real pressure on exhaust quality and smoke visibility. At the same time, because it runs for substantial hours, diesel cost is a material line item in facility operations. In a case like this, RECD and dual fuel aren’t competing solutions — they’re addressing two genuinely separate cost centres for the same organisation: environmental/compliance risk on one side, and operating expense on the other.

The same logic applies to data centres, manufacturing plants with continuous shift operations, and large commercial complexes where the DG set effectively behaves like a prime power source rather than an occasional backup unit.

If this describes your situation, the evaluation gets more technically involved — you’re now looking at how the two systems interact on the same generator, what that means for exhaust routing and controls integration, and whether safety interlocks for both systems can coexist cleanly. This is not a project to plan around assumptions; it needs a proper technical assessment covering both angles.

The Trap of Comparing Headline Numbers

Once facilities understand that RECD and dual fuel solve different problems, there’s a second trap waiting: comparing the two using headline performance numbers as if they measure the same thing. You’ll often see RECD systems marketed around emission-reduction percentages (something like “up to 96% reduction” appears frequently across the industry, including in some of our own materials) and dual fuel systems marketed around diesel-substitution percentages (commonly cited “up to 70%”).

These numbers aren’t comparable to each other, and neither should be treated as a guaranteed outcome for any specific installation. They represent published potential under favourable conditions — established engine health, appropriate load, correct installation, proper maintenance. Your actual result depends on your generator’s condition, how it’s loaded, fuel or gas quality, and how consistently the system is maintained afterward.

We’ve written a full breakdown of why this matters for RECD specifically — worth reading if a proposal for your facility is leaning heavily on a single reduction percentage without asking about your generator’s operating data first.

How to Actually Make the Decision

If you’re still unsure which direction fits your facility, work through these questions roughly in order:

1. What triggered this conversation in the first place? A compliance notice, smoke complaint, or environmental audit finding points toward RECD. A rising fuel budget or cost-reduction mandate points toward dual fuel.

2. How many hours does your DG set actually run per month? Occasional backup-only usage weakens the economic case for dual fuel, since fuel savings need runtime to compound. High, regular runtime strengthens it considerably.

3. Is there a viable gas supply at your site? If there’s no accessible CNG, PNG, or biogas source, dual fuel isn’t realistically on the table regardless of other factors — this alone can settle the decision.

4. What condition is your generator in? Both technologies perform best on a mechanically sound engine. A generator with significant underlying wear may need that addressed first, or may be a better candidate for replacement than either retrofit path — a topic we cover separately in our piece comparing retrofit versus replacement economics.

5. Do you have both a compliance pressure and a cost pressure? If yes, it’s worth evaluating both technologies together as part of one coordinated project rather than two separate initiatives.

Why a Generic Answer Won’t Serve You Well Here

We could end this article with a tidy recommendation, but that would be exactly the kind of one-size-fits-all thinking this comparison is meant to push back against. The honest answer to “which one should I choose” is: it depends on data we don’t have yet — your generator’s make, model, kVA rating, condition, load pattern, operating hours, and whatever gas or fuel infrastructure exists at your site.

That’s not a deflection; it’s the same principle that runs through every stage of a properly run retrofit project, from technical evaluation through to commissioning. Product selection follows data. It doesn’t precede it.

If you’ve read this far and you’re still weighing RECD against dual fuel — or increasingly suspect your facility might need to think about both — the next useful step is a technical assessment grounded in your actual generator and site conditions rather than a general comparison article. You can review our approach on the About Us page, check common questions on our FAQ, or go straight to sharing your DG-set details with our team so we can help you evaluate what fits.

For background on how CPCB frames retrofit requirements more broadly, the CPCB genset notifications page is the authoritative source for current certified-manufacturer lists and applicable emission limits.