Stage V Regulations Post-Brexit

What Would Stage V Emissions Regulations Mean for the UK Post-Brexit?

When Brexit happens, the EU’s Stage V diesel engine emissions standards will stand until the UK government replaces them. But what would they be replaced with?

US Tier 5 vs EU Stage V Regulations

One opinion held that the UK would wait until the US promulgates their version of the Stage V regulations, most likely to be called "Tier 5" in their nomenclature. The UK would naturally want to keep its close ties with the American markets, additionally, the American regulations would be expected to remain virtually identical to the existing EU Stage V emissions standards for diesel generating equipment.

So really, not very much would change.

There are a few good reasons for that. First and foremost, the US regulations will almost certainly fall in line with the EU ones. Many big diesel engine manufacturers are multinational companies who already sell to both US and EU markets. It is far too expensive to have different production lines set up to meet different market regulations, so they are essentially already gearing up to produce EU Stage V emissions-ready diesel generators. For the same reason, the UK government has every reason to continue putting out emissions standards that mirror both the US and EU regulations, for sheer efficiency.

There has been an almost exact parallel between EU and US emissions standards in this regard for the better part of a decade. There has long been an assumption that the EPA (US Environmental Protection Agency) would essentially clone the EU Stage V emissions standards, just as they have done before with Stage III / Tier 3, Stage IV / Tier 4 and Stage IIIb / Tier 4 Interim. However, the current administration shows no sign of movement on this front. The EPA hasn't said much about its plans, though California, a big enough market to make international changes on its own, has hinted that they could implement Tier 5-type regulations on a state level.

Another important point is that the EU's Stage V emissions standards are not all that difficult to meet, nor are they likely to change dramatically. Most of the industry leading manufacturers say that a hypothetical US Tier 5 would be almost identical to their existing Tier 4 Final in any case.

Like the EU's Stage V, any UK Stage/Tier 5 regulations will likely apply to all mobile diesel generators.

What Equipment Would Stage V Regulations Apply To?

Stage V regulations of course apply to excavators, wheeled loaders and tractors, but they also apply to mobile gensets - both those built on mobile trailers and those commonly transported to work locations by truck, such as those offered by equipment rental and plant hire companies. The only non Stage V gensets would be those which are permanently installed in a single location, such as emergency standby generators.

Would Anything Be Different Under a US-Style Stage V?

Unlikely, but possibly. Stage V applies to all appropriate engines, regardless of horsepower, so a hypothetical UK Stage 5 is likely to do so as well. This is a shift from Stage IV, where engines of less than 24 horsepower were exempted. This won't matter for most industrial or commercial Stage V genset users, but may be more important for home, camping & leisure users.

Many in the US are pushing for regulations with substantially lower NOx limits for smaller engines as well. It is not guaranteed that this will be an exact parallel with the EU's Stage V standards, and there will probably be quite a bit of wrangling (and lobbying) before those numbers would be set.

Would US-Style Stage V Diesel Generators Require New Technology?

Almost certainly not. Stage V certainly didn't call for anything radical. Industry experts are certain that off-the-shelf solutions for whatever standards are eventually decided on are already available. Any US version would be expected to require the same standards.

There are likely to be different technologies developed to meet Stage V Emissions Regulations more efficiently for different sizes, types and applications of diesel engines. However, there is no "magic bullet" technology which would be likely to change the designs of all engines, such as the Diesel Particulate Filter (DPF).

The core changes would almost certainly require less particulate emissions, especially sub-micron level soot. The current medical understanding is that these can become easily lodged in the lungs, and do cause long term problems.

However, the technology to catch sub-micron level soot (DPFs) already exist and work quite well. These have been required for certain engine types ever since Stage III for larger particulates. Simply making diesel particulate filters more effective at catching microscopic particles as well does not require any novel technologies.

Particulate matter filters are already much more advanced than Stage III or IV regulations require. The older type of filters needed to be periodically "regenerated", so that accumulated soot could be burned away from the inside of the filter. Even so, they eventually clogged with ash, and needed to be replaced or cleaned.

In response, both the engines and the filters were redesigned. Smaller engines were re-engineered so that they met the particulate matter emissions standards without any filters at all. This wasn't practical for engines of more than 75 horsepower, so most of these are already fitted with modern, more efficient DPF filters. Simply swapping them out at the manufacturing stage with new Stage V emissions compliant filter types will be easy.

The only real change necessary to comply with Stage V (and therefore likely for a US Tier 5 type regime as well) is in the manufacture of 19 kW to 37 kW diesel gensets. Many of these had not needed exhaust after-treatment or common rail fuel systems in the past. Even then, the changes are already being made to almost all production lines in order to sell their products in Europe, so applying a similar requirement to mobile diesel generators destined for sale in the UK should not impose too great of a burden.

Most experts say that all engines, small and large, will soon have Stage V compliant DPFs fitted in any case. Making them Tier 5 compliant as well may not even require any changes. However, the current Stage V and likely Tier 5 emissions standards are likely to drive additional advances in DPFs.

In the end, adapting to Stage V took very little radical change on the part of manufacturers. The same will likely be true for EPA Tier 5 when it is imposed.

EU Stage V Emissions Standards
If a New UK Stage 5 Follows a US Tier 5, What Transition Period Can We Expect?

The EU's Stage V (the equivalent of US Tier 5 emissions regulations) are due to be phased in in 2019/2020, and by and large the industry is comfortable with them and the time frame. They will be producing EU Stage V compliant equipment in 2019 and 2020 already, and any heightened requirements that a new UK Stage 5 would add are expected to be minor. They would almost certainly have a delay period similar to the EU regulations as well, and wouldn't likely apply until well after 2020.

Under the EU's Stage V scheme, large original equipment manufacturers had 18 months to "use up" the last of their stocks of non-compliant engines and equipment, as well as a further 6 months to get them onto the market. Smaller manufacturers (those who produced less than 100 units a year) were allowed an additional year to sell the last of their non-compliant units.

If a UK Stage 5 emissions standard follows the same pattern of transition as the EU's Stage V, many manufacturers could be selling gensets not compliant with Stage V until at least 2021. That is assuming some kind of UK Stage 5 regulations are adopted before the end of the year, something which seems extremely unlikely.

For more information, or to discuss your requirements with our team of experts, call us on +44 (0) 1977 657 982 or email us at

All Generators Stage IIIa Emissions Standards

Share this Post

Blog published by ADE Power on March 8th, 2018

For more information about our range of generators

Get in touch to speak with our experts.

We use cookies to improve your experience and analyse website traffic. Read more about how we use cookies in our Privacy & Cookie Policy.