Why the technical argument is so good
When you buy electricity from the grid, that energy was generated at a power plant that threw away most of the fuel's energy as heat. And when your boiler produces steam, it turns fuel into heat without using any of the mechanical work that fuel could have provided.
They are two separate processes, each one wasting on a different side. Cogeneration joins them: a gas engine drives an electric generator, and the heat that engine would throw away is recovered and goes into your process.
There are two usable sources. The engine's cooling circuit, between 70 and 90 °C, serves for process hot water. The exhaust gases, between 400 and 500 °C, serve for steam or, through an absorption chiller, for chilled water. That last case is the one that most surprises plant people: cooling with heat.
That is why, when the conditions are there, cogeneration is the only case in which producing your own energy is genuinely more efficient than buying it. It is not a preference: it is thermodynamics.
The first piece of data: your boiler's real hours
The practical threshold is around 6,000 hours a year. Below that the engine runs little, the capital sits idle most of the time and the payback stretches beyond what any committee approves.
And here is the most common mistake: using design hours instead of real hours. Many plants believe their boiler runs continuously, and on checking the log it turns out it stops on Sundays, drops in the low season and is off two weeks a year for maintenance.
The hours are verified, not estimated. They come from your own boiler's operating log, and they are the first filter: if they do not pass, there is no project, and it is better to know before paying for engineering.
The second piece of data: the spread between gas and electricity
A cogeneration project lives on the difference between what you pay for gas and what you pay for electricity. That spread is the margin all the return comes from.
If the spread is wide, the project is solid and withstands variations. If it is narrow, the project is fragile: a move in the gas price eats it up, and you are left with an engine that does not pay for itself and a long-term supply contract on top.
That is why the spread is modeled from the start and with your real prices, not with market averages. And it is modeled with scenarios: what happens if gas goes up twenty percent, what happens if the electricity tariff goes down. A project that only works in the base scenario is not a project, it is a bet.
The third piece of data, which almost nobody checks: at what temperature you use the heat
Having thermal demand is not enough: you have to be able to use the heat the engine delivers. If your process needs very high-temperature heat and cannot use 70 to 90 °C water or 400 to 500 °C gases, recovery falls short and the case weakens even if the hours add up.
The reverse also happens, and it is good news: plants that thought they had no use for the heat discover that they do — feedwater preheating, CIP cleaning, drying, or absorption cooling, which turns heat into process air conditioning.
That evaluation is the heat balance, and it is the first thing done. Before talking about engine brands you need to know what heat you use, at what temperature and for how many hours.
Where the regulatory boundary lies
In distributed generation (DG), below the threshold that requires a permit, the project is developed without the generation permit procedure. That is the ground we work on.
Above 0.7 MW the project requires a permit, with its own filing window and timelines, and that changes the schedule and the capital profile. We do that too: at that scale development is led by GIS Power, of the same group, and the team that evaluated your thermal process stays at the table. What changes is who signs the permit, not who you are talking to.
It is a regulatory boundary, not a technical one. It is worth knowing before sizing, because a project that crosses the threshold by a small margin is sometimes best adjusted and sometimes best taken to the other side. Both are legitimate decisions; what is not legitimate is finding out afterward.
The right order for the conversation
Real boiler hours. If they fall short, it ends there and we tell you.
Heat balance: what heat you use, at what temperature and with what continuity. That is where the capacity comes from, not from electricity consumption.
Gas-electricity spread with your prices and with scenarios. That is where the return comes from.
And only then the selection of the engine-generator set, which is quoted directly with the manufacturer. Selecting the engine first and looking for the case afterward is exactly the order that produces projects that do not pay for themselves.
How many hours a year does your boiler really run, according to the log and not the design? And what is your real spread between gas and electricity? With those two answers we know in twenty minutes whether it is worth continuing.
