Steam Solutions Comparison

What is the difference between an industrial (pressure) boiler and a steam generator?

Boilers are slow for steam production compared to steam generators. Boilers create steam by boiling water in a heated pressure vessel. As the water boils at its boiling point (the boiling temperature depends on the pressure generated), steam is obtained at the saturated pressure. This type of steam making represents older steam technology. Boilers require high pressure to get to high temperatures; e.g., 200°C requires 225 psi pressure capability. Even at 100 Bars, the saturation temperature is only 311°C.   Thus saturated or boiler steam may be wet and contain water droplets. Traditional pressure boilers make saturated steam that can sometimes be mildly superheated.

On the other hand, steam generators are modern rapid steam production devices with instant on-off features, steam velocity control features, independent backpressure control, and significant high-temperature steam capability (without the need for pressure vessels or pressure unless required for the backpressure). Steam generators do not have to operate at high pressure for the high temperature- typically thus offer high-temperature dry steam.   Temperatures of 1000°C can be obtained with no pressure requirement.

Choose a clean electric steam generator if your required temperature is above 120°C, pure steam is required, a variable flow rate may be necessary, and adjustable temperature and low footprint are essential. Because of its energy efficiency, controllability, and on-off features without idling, a steam generator may be the most economical choice. (Scroll below for more comparisons)

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Steam Generators can operate at room pressure or at the backpressure required to be overcome to yield the needed temperature of 200°C, 300°C, 400°C, 500°C, 600°C, 700°C, 800°C, and even up to 1300°C. Thus, one can get high temperatures in the steam gas without the use of unwieldy pressures.

  1. Temperature Limitations – Industrial boilers require high pressures for higher temperatures. Not so for steam generators.
  2.  Boilers typically sacrifice efficiency or safety to operate at lower temperatures than rated. Not so for steam generators. As a boiler’s pressure rating increases, its efficiency often falls.
  3. Combustion Process – Nearly all large-scale industrial boilers utilize the combustion process. Combustion adds to CO2 and NOX production as well as fossil fuel consumption. Combustion processes typically result in low efficiencies and high energy losses. What is the cost of climate pollution?
  4. Safety – Pressure vessels can fail and explode (although this is rare as many boilermakers follow the best practices). Low water levels can result in boiler overheating and potentially the explode. Gas leaks pose an inhalation danger as well as an explosion risk.
  5. Certifications  – Any boiler or pressure vessels require certificates and inspections. Open flow steam generators may not require special and yearly credentials by several criteria. Review the boiler regulations for your state. Regulations are typical in Canada Canada.
  6. Difficult to Use Boilers – Boiler operation typically depends on specific, trained individuals who are trained to read dials and follow numerous safety measures per local code. Boilers are complicated.

Steam Generators use 21st-century technology—no combustion or pressure vessels. The GHGA, MHGA, OAB, and HGA patented technologies allow steam generators to operate with unparalleled efficiencies, saving you time and money and improving your process. Industrial boilers have worked well in the past, but they are 19th and 20th-century type technology machines with low efficiencies. They can reach 85% efficiency in many configurations (only at a steady state which often takes long for boilers), but they still have significant drawbacks in temperature capability. As the pressure rating increases, the efficiency falls very often for boilers. Steam generators, like the GHGA, MHGA, OAB, or HGA type, routinely offer over 95% efficiency even to 1000°C and beyond  (a temperature unimaginable for boiler steam).

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Feature  OAB® Steam or GHGA Steam Water Tube Steam Boilers, Non-Electric Electric High-Pressure Steam Boilers
Maximum Steam Temperature1

Always Clean Steam?

120-1300°C Standard. Choice of Models. Always high flow. No moisture. High performance.


Mainly 121C. Sometimes up to 600°C with Economizer and Superheater. Achieving a steady state takes a long time for boilers.


134°C for 3 Bar steam.


Delivery to Initial Startup.

How Versatile

Models are easily installed in a day, and there is no anticipated wait for certifications to start.

Independent temperature, flow, and pressure settings


Not all types are versatile or compact.

Small units could be plug-and-play. Large units may require certification time.

Generally not versatile.

Efficiency >90-98% <85-90% (at steady state much lower otherwise) ~85-95% (at steady state much lower otherwise)
Idle Energy Waste None (Choice of Continuous or On-off Steady-state steam) High Moderate
Non-Steam Producing Energy Usage Time
(Start-Up Time2)
Start and Stop. Nearly Instant. Generally within a minute. 60+ Minutes. Becomes slower with higher pressures and volume requirements ~60 Minutes. Becomes slower with higher pressures and volumes. (Time does not include cool down and pressure release durations for autoclaves)
Suggested Inlet Temperature/Pressure3 Tap/Tap Pressure RO type water 40-60°F. Water has to be conditioned. 20-35°C. Water has to be conditioned.
Capital Cost per Kg of Steam3 Low. Financing is available when qualified. High Moderate. Depends on the temperature/pressure required.
Operational Costs4 Low even up to 1300°C.

Modern HMI and PLC controls. Touch screen operation.

High Low-Moderate
Unit Footprint Starting at 1’x 1’x 1′.  A typical 180 KW unit is 4ft x 4 ft.  Small and remotely locatable power panels. Depends on the steam rate required. Large Depends on size and pressure requirements.
Plug & Play Operations Yes No No
Requires Boiler Certifications5

Review the boiler regulations for your state. Canada. 

Generally, No Yes Yes
Downtime6 Low (Unit can be used for continuous steady-state steam). Because of the low footprint and modular designs, the MHI-Never-Down Service™ is available for all steam units.

Self Draining

Self Flushing


It may require complex flushing and draining operations.


It may require complex flushing and draining operations.

Utilizes Combustion Heat 7 (Requires Ventilation)

Combustion creates CO2 and NOx

No Yes. High social cost. In the future, we may have carbon taxes when applicable. No
Energy Needed to produce 100 Kg/hr steam from a cold start ~70 kWh for steam  @~200°C. Water at Room Temperature to Steam. ~150-200 kWh Equivalent (Including start-up time consumption). Not always reported from room temperature water. ~150kWh Equivalent (Including start-up time consumption). Not always reported from room temperature water.
Power Weight [Kg Equipment/(Kg/hr) of steam] for a 100kW Generator ~2 Kg per Kg/hr of steam. Variable. ~5 Kg/hr of steam (Weight increases with temperature/pressure). Variable
Maximum Work Potential (Based on second law limitation) Base is 1 Bar 100C liquid water for all. 672 kJ/Kg for 500°C superheated steam
1973 kJ/Kg for 1300°C superheated steam
755 kJ/Kg for 10 Bar saturated steam
1169 kJ/Kg at 100 Bar saturated steam.
Generally not used for creating work.
Enthalpy (heat) Content 3489 kJ/Kg for 500°C superheated steam at 1 Bar 2777 kJ/Kg for 10 Bar saturated steam
Saturation steam temperature 180°C
2725 kJ/Kg for 3 Bar saturated steam
Saturation steam temperature 134°C
Running at Partial Capacity With MHI Electronic Controls, No loss of efficiency significantly significantly Significantly lower efficiencies, even if the model is capable Lower efficiencies
Air Contamination Effects Extremely high operation temperatures diminish the effects of contaminated air, if any. Air contamination harms output No air contamination is allowed (strict)
Piping Losses Discrete, locatable units reduce necessary piping. The one-atmosphere pipe can be better insulated and lighter. High pipeline pressure combined with long piping distances leads to heat loss and dangerous conditions in the event of pipe failure. Pipes can be heavy. High pipeline pressure combined with long piping distances leads to heat loss and dangerous conditions in the event of pipe failure. Pipes can be heavy.
How far can I run my pipe? Info-graphic. Low piping loses. Variable. Unknown. Unknown.
Typical Improved Efficiencies (Energy) Application dependent – sometimes over 50% better improvement over combustion.
Improved Water Efficiency Application dependent – sometimes over 50% better improvement over combustion. Not efficient Moderate efficiency
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Steam Without the Wait

MHI has an energy-efficient high-productivity solution for your steam application with new steam technology for high-quality steam. The BoilerFreeTM technology allows nearly instant steam production. Most MHI steam generators produce super-heated in under a minute from a cold start (it can take a boiler many hours or days). Please contact MHI.

Modern Steam Sensors Work Hard For You.    Did you know that the steam generator units constantly monitor the incoming electric phases for any imbalance, allow variable water flow, keep an eye on the quality of the water in the reservoir, display steam temperature, and much more?

Modern Steam Generator

Modern OAB® Steam Generator

OAB installation for packaging.

OAB installation for packaging.





Compare the footprint of boilers and steam generators.

Want to find out how MHI can help you meet your steam needs?

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We will help find a good solution to meet your needs.