Cogeneration and trigeneration systems enable the harnessing of otherwise excess heat, steam and/or other gases, significantly improving the overall efficiency of energy use in electric power generation. By using heat that would otherwise be lost, a cogeneration system can make use of 70–80% of the energy in the original fuel, compared to around 25–35% for a conventional, subcritical coal-fired power station. Another advantage of cogeneration and trigeneration systems is that by generating electricity locally, they avoid transmission and distribution network losses, which can be as high as 10%.

Cogeneration systems produce electrical power while capturing and utilising the heat that arises as a by-product of the process. Trigeneration uses some of the remaining lower grade heat for cooling as well as capturing heat from the initial power generation. Systems typically have returns on investment in the range of 5–20% and can reduce energy demand and greenhouse gas emissions by as much as 20–30%.[1. UK Carbon Trust (2010) Introducing Combined Heat and Power. The Carbon Trust.]

Both cogeneration and trigeneration systems are appropriate to use at sites that have high demand for heating, such as hotels, hospitals, industrial laundries, data centres and swimming pools. They are especially cost effective when heating and/or cooling demands are present throughout the year.

Trigeneration can be cost effective in facilities such as large data centres, which require onsite electricity generation and have substantial year-round cooling requirements. In these cases, the heat by-product of the power generation process can be used for cooling using an absorption chiller.

Developments in small-scale technologies such as microturbines and fuel cells are also opening up new opportunities for the application of cogeneration systems.[2. Worrell, E. and Galitsky, C. (2004) Emerging Energy-Efficient Technologies in Industry: Case Studies of Selected Technologies, Ernest Orlando Lawrence Berkeley National Laboratory - Environmental Energy Technologies Division]