8 April 2010 – Caterpillar has announced its portfolio of technologies to meet Tier 4 Interim emissions regulations for mobile and stationary generator sets in the US.
The US Environmental Protection Agency (EPA) will introduce the next phase of its Tier 4 emissions control regulations in January 2011.
These significantly limit emissions of oxides of nitrogen (NOx), particulate matter, hydrocarbons and carbon monoxide, and will affect the majority of non-road mobile equipment powered by diesel engines greater than 130 bkW, including mobile generator sets.
Stationary diesel engines, such as those used in standby and prime power generator sets, are regulated separately, but to similar standards as non-road mobile equipment.
However, the challenges facing the electrical power industry are unique in a number of areas, particularly above 900 bkW, where the regulations focus on reducing NOx emissions from generator sets by 90%, compared to a 45% reduction for other equipment types, says Caterpillar
To provide power customers with the most economical and efficient emissions solutions, Caterpillar has developed three different engine-integrated technology packages which can be used in combination to address the various emission reduction levels required by the EPA regulations. 
The technologies have been developed, in conjunction with the wide range of Cat engines, to provide optimal performance while minimizing impact on generator set space requirements and maintenance hours. However, customers can expect a 25–50% price increase on Tier 4 Interim generator set packages.
Cat Tier 4 generator sets are capable of integrating into larger power systems that could include UPS, switchgear and ATS products. To support this new line of generator sets, Cat dealers and technicians will be factory trained in emissions technology installation and service.