Nameplate rating is the number on the plate, not the number you will get. This calculator shows what a gas genset from 50 kW to 2,000 kW actually delivers at your site altitude, ambient temperature and gas quality, and what your fuel needs in the way of gas treatment before it arrives at the engine.
| Derated continuous output | — |
|---|---|
| Nameplate to select | — |
| Your running load | — |
| Headroom remaining | — |
| Estimated fuel use at full load | — |
| Electrical efficiency band | — |
A nameplate rating assumes a reference fuel, sea level and a 25°C ambient. Every departure from those conditions costs power. This is the working order our engineers apply before they size anything.
Above 1,000 m the air thins and the engine makes less power. Budget roughly 3% per 100 m of altitude above 1,000 m. A 2 MW set at 3,000 m is around 1.3 MW on the plate. Some engines can be re-rated for altitude at build stage, which recovers a large part of this — tell us the site elevation so we select accordingly.
Below roughly 70% methane the charge energy per cycle falls and output on the same nameplate drops. Digester gas at 55-65% methane commonly yields only 60-80% of the natural gas rating. This is the single most common reason a customer receives fewer kW than expected, and it is entirely avoidable in the specification.
Above about 40°C the set cannot cool itself as well, so continuous output is commonly limited by around 1% per degree. Desert and Middle East sites should also be checked for enclosure type — an open skid with remote radiator copes better than a canopy.
These do not add linearly in the field, but they do stack. A 2,000 m site on 60% methane biogas can be half the nameplate in real terms. This is why we quote derated continuous ratings against a stated gas analysis rather than publishing a single headline number per model.
H₂S above a few hundred ppm requires desulfurization, and moisture control usually has to come with it. Desulfurization, dehumidification and pressure regulation are quoted as a package matched to your gas, not left to be discovered after the order.
Motors and compressors can draw 3-6× their running current for several seconds. Your load profile needs to be looked at, not just your kW total — especially on a single set carrying large motor loads.
A naturally aspirated or turbocharged spark-ignited gas engine loses roughly 3% of its rated output per 100 m of altitude above 1,000 m, because the air the engine breathes becomes thinner. At 2,000 m a 1,000 kW set is typically derated by about 30% to around 700 kW, and at 3,000 m by about 60%. Engines that can be re-rated for altitude at build stage lose far less. The correct practice is to state the altitude in the enquiry so the model is selected on derated rating rather than nameplate.
The nameplate rating assumes a reference fuel with a defined methane content and lower heating value. Landfill gas and farm digester gas commonly sit at 55-70% methane with a lower heating value of 18-24 MJ/Nm³, well below pipeline natural gas at 90-95% methane. Below roughly 70% methane the charge energy per cycle falls, and output on the same nameplate drops accordingly — often to 60-80% of the natural gas rating. This is why a biogas project must be quoted on the derated rating for the specific gas analysis, not on the catalogue number.
Hydrogen sulfide is corrosive to cylinder heads, valves and exhaust parts, and it shortens overhaul interval dramatically. Desulfurization is mandatory for any gas above a few hundred ppm. Typical raw digester gas is 2,000-8,000 ppm, and a treatment package is normally required to bring the gas down to an acceptable level before it reaches the engine. Dew point and moisture must be controlled at the same time, because wet gas destabilizes the charge and causes unstable running.
Yes, modestly. Above roughly 40°C the engine cannot cool itself as effectively, so the continuous rating is commonly limited — around 1% per degree C above 40. A set rated 1,000 kW in a 50°C desert site may be limited to roughly 900 kW. Radiator sizing and the enclosure type matter here: an open skid with a remote radiator handles a high-ambient site better than a sound-attenuated canopy.
For prime power running 24 hours a day, size the set so that the derated continuous rating still covers the running load with 10-15% headroom. So a 900 kW running load at 2,000 m altitude, on a 65% methane biogas, needs a nameplate closer to 1,400-1,600 kW. For standby duty, where the set runs rarely and the diesel alternative is the benchmark, you can size closer to the load but must still allow for motor starting current. Motor starting can demand 3-6 times running current for several seconds, which must be checked against the alternator.
No. The output is indicative and is intended to help you frame an enquiry, not to fix a price or a guaranteed rating. A firm selection requires the full gas analysis including methane, higher and lower heating value, H₂S, moisture, dew point and inlet pressure, plus your load profile, altitude, ambient temperature and required voltage and frequency. Send those and we return a configured selection with a guaranteed continuous rating on your specific fuel.
Send us the gas analysis and load profile and we will turn them into a configured selection with a guaranteed continuous rating on your fuel.
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