A CHP system, or combined heat and power system, generates electricity and useful heat from a single fuel source at the same time. Instead of burning fuel just to make electricity (and venting the leftover heat into the atmosphere), a CHP system captures that byproduct heat and puts it to work, typically as steam or hot water. This dual output is why CHP is also called cogeneration. The result is a dramatic jump in fuel efficiency: conventional separate systems for electricity and heating are roughly 50 to 55 percent efficient, while CHP systems routinely reach 65 to 80 percent, with some approaching 90 percent.
How a CHP System Works
Every CHP system has three core components: a prime mover (the engine or turbine that burns fuel), a generator (which converts mechanical energy into electricity), and a heat recovery unit (which captures thermal energy that would otherwise be lost). The prime mover burns a fuel, most commonly natural gas, to spin the generator and produce electricity. The heat recovery unit then extracts heat from the exhaust gases or cooling systems and converts it into steam or hot water that can be used for space heating, industrial processes, or domestic hot water.
There are two main configurations. In the first, a combustion turbine or reciprocating engine burns fuel to drive a generator, and a heat recovery device captures exhaust heat. In the second, a boiler produces steam that first spins a steam turbine to generate electricity, and the lower-pressure steam exiting the turbine is then routed to meet heating needs. Both approaches share the same principle: squeeze as much useful energy as possible from every unit of fuel.
Types of CHP Technology
The “prime mover” is the defining feature of any CHP installation, and there are several options depending on the size and needs of the facility.
Reciprocating engines are among the most common for smaller applications. They work like a car engine, burning natural gas, biogas, or propane, and achieve electrical efficiencies of 25 to 50 percent. They range from 50 kilowatts to about 5 megawatts and are well suited for buildings that need a steady supply of hot water or low-pressure steam. Installed costs run roughly $800 to $1,500 per kilowatt of capacity.
Gas turbines are the workhorse of larger industrial and institutional CHP. They handle loads from about 3 megawatts up to 200 megawatts and achieve 25 to 40 percent electrical efficiency on their own. Adding a heat recovery steam generator to the exhaust stream is what transforms a simple gas turbine into a high-efficiency CHP plant. Installation costs are lower per kilowatt, typically $700 to $900.
Microturbines are a scaled-down version of gas turbines, producing 25 kilowatts to 250 kilowatts. Most designs include a built-in recuperator that preheats combustion air using exhaust heat, bringing electrical efficiency to the 20 to 30 percent range. Their compact size makes them practical for commercial buildings and smaller facilities.
Fuel cells generate electricity through an electrochemical reaction rather than combustion, which makes them the cleanest option. They achieve the highest electrical efficiencies of any CHP technology, between 40 and 70 percent, and produce virtually no nitrogen oxide emissions. The tradeoff is cost: installations currently exceed $3,000 per kilowatt, limiting fuel cells to specialized applications for now.
Fuel Sources
Natural gas dominates the CHP landscape because it’s widely available, relatively affordable, and burns cleaner than coal or oil. Biogas captured from landfills, wastewater treatment plants, or agricultural digesters is another option, particularly appealing because it turns a waste product into energy. Propane and diesel fuel are used in some installations, especially in remote locations or as backup.
Hydrogen is gaining attention as a future CHP fuel because it produces zero carbon emissions when consumed. Researchers are exploring how renewable energy sources like wind and solar can power hydrogen production, creating a fully clean supply chain for hydrogen-based CHP. For now, most systems still rely on fossil fuels, but the technology is being actively developed as a pathway to decarbonization.
Efficiency and Emissions Benefits
The efficiency advantage of CHP comes down to simple physics. A conventional power plant converts fuel into electricity at roughly 33 to 45 percent efficiency, and the remaining energy escapes as waste heat through cooling towers and exhaust stacks. If you then run a separate boiler at your building to produce heat, that’s another round of fuel burned at its own efficiency losses. Combined, the two separate systems use fuel at about 50 to 55 percent efficiency.
A CHP system collapses those two steps into one. By capturing and using the waste heat on-site, total fuel utilization jumps to 65 to 80 percent or higher. That means less fuel burned for the same amount of useful energy, which directly translates to lower emissions. The EPA estimates that a conventional 1-megawatt CHP system produces about 4,200 tons of CO₂ per year, compared to 8,300 tons for the equivalent combination of grid electricity and a standard boiler. That’s roughly half the carbon footprint.
Where CHP Systems Are Used
CHP works best in facilities that need both electricity and heat for long stretches of the day, making certain settings natural fits. Hospitals rely on CHP for the constant hot water, steam sterilization, and reliable backup power their operations demand. Universities and college campuses use CHP to serve clusters of buildings with district heating while generating their own electricity. Industrial facilities like paper mills, chemical plants, breweries, and food processors have large, steady thermal loads that align perfectly with cogeneration.
Other common installations include data centers (which need reliable power and can repurpose waste heat), wastewater treatment plants (which can fuel CHP with the biogas they already produce), and large commercial buildings. Even automotive manufacturing plants and ethanol production facilities have adopted CHP to reduce energy costs and improve resilience against grid outages.
Residential and Small-Scale CHP
Micro-CHP systems bring cogeneration down to the scale of a single building. A residential or small multifamily unit might produce 1.2 to 4.4 kilowatts of electricity while simultaneously delivering 13,000 to 42,000 BTUs per hour of hot water at 160°F. These systems replace or supplement a conventional boiler, and because they follow the building’s thermal demand, they run for extended periods without the constant on-off cycling of a standard boiler.
In one multifamily building case study, a micro-CHP system replaced the operation of a 210,000 BTU natural gas boiler used for domestic hot water. During months with comparable weather to the previous year, gas consumption dropped an average of 27 percent. Tenants reported faster hot water delivery, and the building owner saved approximately $6,400 in the first year of operation. For apartment buildings, senior living facilities, and other multifamily properties with consistent hot water demand, micro-CHP can be a practical investment.
Costs and Payback
Upfront costs for CHP vary widely based on the technology and scale. Gas turbines at the larger end cost $700 to $900 per kilowatt installed, while reciprocating engines and microturbines fall in the $800 to $1,500 range. Fuel cells remain the most expensive at over $3,000 per kilowatt. These figures cover the equipment, installation, and integration with existing building systems.
The payback period depends on local electricity and gas prices, how many hours per year the system runs, and whether incentives or rebates are available. Energy efficiency projects with heat recovery components have demonstrated simple payback periods in the range of 3 to 5 years in well-matched applications. State energy programs, like those offered by NYSERDA in New York, provide incentives that can shorten that timeline further. The ongoing savings come from reduced electricity purchases, lower fuel consumption for heating, and in some cases the ability to sell excess electricity back to the grid.