CPCB IV+ genset norms: what changed and what it means for buyers

Every new diesel genset up to 800 kW sold in India now has to meet the CPCB IV+ emission limits. For the sizes most businesses buy, the limit on soot (particulate matter) is 90% lower than under the old CPCB II rules, and the limit on nitrogen oxides and hydrocarbons together is about 85% lower. Here is what the rule says, what changed for each size of set, and what it means if you are buying a new set or running an old one.

What is CPCB IV+?

CPCB IV+ is the common name for the revised emission standards for genset engines up to 800 kW, notified by the Ministry of Environment, Forest and Climate Change as G.S.R. 804(E) on 3 November 2022. The Central Pollution Control Board (CPCB) then issued the test and approval procedure, the "System and Procedure", in March 2023.

The limits apply from 1 July 2023. They cover diesel engines and spark-ignition (petrol and gas) engines above 800 cc, and there is a separate table for small portable petrol and gas sets up to 19 kW. One standard now covers both prime and standby sets and all fuels, as Mahindra Powerol and Cummins India both point out in their notes on the norm.

The rule works through type approval. A maker, importer or assembler has to get each engine approved by an authorised certifying agency and pass conformity of production tests. As a buyer, you check that the set you are offered carries that approval.

CPCB IV+ limits vs CPCB II, by size

Limits are in grams per kWh of engine output, measured on a test cycle. The power bands are by the engine's gross mechanical power in kW, not by the genset's kVA.

Engine power	CPCB II: NOx + HC	CPCB II: PM	CPCB IV+: NOx	CPCB IV+: HC	CPCB IV+: PM
Up to 8 kW	7.5	0.30	7.5 (NOx + HC)		0.30
8 to 19 kW	7.5	0.30	4.7 (NOx + HC)		0.30
19 to 56 kW	4.7	0.30	4.7 (NOx + HC)		0.03
56 to 560 kW	4.0	0.20	0.40	0.19	0.02
560 to 800 kW	4.0	0.20	0.67	0.19	0.03

The carbon monoxide limit stays at 3.5 g/kWh in every band, and the smoke limit stays at 0.7 per metre (light absorption). CPCB II here means the limits notified as G.S.R. 771(E) in December 2013, which applied from April 2014. The old bands were drawn slightly differently (up to 19 kW, 19 to 75 kW and 75 to 800 kW); the table puts each new band next to the old limit that applied to it.

Three things stand out:

• The smallest sets, up to 8 kW, did not change.
• Sets from 19 to 56 kW keep the same NOx + HC limit, but the soot limit falls from 0.30 to 0.03 g/kWh, a tenth of what it was.
• Sets above 56 kW, which covers most commercial and industrial gensets, now have separate, much tighter limits for NOx and for hydrocarbons. Add the two and the total is 0.59 g/kWh, against 4.0 before.

Cummins India's launch statement in July 2023 described the cut in particulate matter and NOx as about 90% against CPCB II.

A worked example: a 125 kVA set

A 125 kVA genset gives 100 kW of electrical output at a 0.8 power factor (see our genset sizing guide). The engine has to produce more than 100 kW to drive the alternator, so it falls in the 56 to 560 kW band.

On the test cycle, an engine of that size producing 100 kWh of work may now emit up to 2 grams of particulate matter. Under CPCB II the limit was 20 grams for the same work. For NOx and hydrocarbons together, the ceiling falls from 400 grams to 59 grams.

Sets near a band edge need care. A set of around 62.5 kVA (50 kW electrical) sits close to the 56 kW line, and its engine may fall on either side depending on the model. The engine's gross power is on the spec sheet; ask the dealer which band the type approval is for.

How do makers meet the new limits?

Tighter limits mean more hardware on the engine and in the exhaust. What each maker fits differs by size:

• Kirloskar Oil Engines says its 25 to 58.5 kVA CPCB IV+ sets use a maintenance-free EGR (exhaust gas recirculation) and DOC (diesel oxidation catalyst) system.
• Mahindra Powerol's notes describe the DOC, which cuts carbon monoxide, hydrocarbons and particulate matter, and SCR (selective catalytic reduction), which turns NOx into nitrogen and water through a chemical reaction.
• Cummins India says its CPCB IV+ sets use after-treatment, an advanced engine control module and remote monitoring.

If the set you are offered uses SCR, it needs a urea-based fluid (diesel exhaust fluid, or DEF) topped up alongside the diesel. Ask the dealer whether your model uses it and how much it uses at your load, and add that to the running cost. Our fuel consumption guide covers the diesel side.

What does CPCB IV+ cost buyers?

Makers do not publish a single figure for how much more a CPCB IV+ set costs than the CPCB II set it replaced, and the gap differs by size and maker. The extra cost comes from the electronics and exhaust treatment above, plus fluid and service items on sets that use SCR. When you compare quotes, check four things: the CPCB IV+ type approval and power band of the engine, the prime rating, whether the set needs DEF, and the service terms for the after-treatment parts.

Can you still buy a CPCB II set?

Not as a new set within the 800 kW limit. A transition period allowed some CPCB II sets to be sold after July 2023; Mahindra Powerol's note says the sale of CPCB II sets is prohibited after 1 July 2024.

Engines above 800 kW are outside CPCB IV+. They follow the older standards notified as G.S.R. 489(E) in July 2002.

What about the genset you already own?

CPCB IV+ does not order existing sets to be scrapped. But state pollution control boards can add conditions. A Kerala State Pollution Control Board order of 28 September 2024 records CPCB's clarification that engines built to the 2002 or 2013 norms, once five years old from manufacture, are to be fitted with a retro-fit emission control device (RECD) under CPCB's procedure of January 2023. The same order says sets that meet the CPCB IV+ limits do not need an RECD. Earlier Kerala orders asked for devices that capture at least 70% of particulate matter.

Rules and deadlines can differ from state to state. Check your state board's current order before planning a retrofit or a replacement.

Cummins India and Kirloskar Oil Engines are among the listed makers selling CPCB IV+ sets; their latest results are on their pages (Cummins India, Kirloskar Oil Engines).

Sources: Ministry of Environment, Forest and Climate Change, G.S.R. 804(E) dated 3 November 2022 (limits as reproduced in Kerala State Pollution Control Board order KSPCB/226/2022-SEE-3 dated 28 September 2024, which also covers RECD retrofits and G.S.R. 489(E)); CPCB, System and Procedure for compliance to the revised emission standards, March 2023 (as reported by Lexplosion); CPCB II limits under G.S.R. 771(E) of December 2013, as summarised by DieselNet; Mahindra Powerol, notes on CPCB IV+ norms and CPCB IV+ gensets; Kirloskar Oil Engines, CPCB IV+ 25 kVA to 58.5 kVA product page; Cummins India launch statement, July 2023, as reported by Autocar Professional.