Views: 0 Author: Site Editor Publish Time: 2026-06-08 Origin: Site
A diesel generator datasheet is a one- or two-page document that contains almost everything you need to evaluate a generator set. The problem is that most of it is written in engineering shorthand — abbreviations, unit conventions, and test condition footnotes that are clear to a generator engineer and opaque to everyone else.
Most buyers read two numbers: the kVA rating and the price. Experienced buyers read the whole datasheet — and they know which numbers matter, which ones are marketing, and which footnotes change the meaning of the headline figures. The difference between reading a datasheet correctly and reading it carelessly can be the difference between a generator that meets your requirement and one that is 20% short of it.
This guide walks through a generator datasheet section by section. We explain every significant field in plain language, tell you what a good value looks like, and flag the red flags that signal a specification worth questioning.
Generator datasheets vary in format between manufacturers, but the information they contain follows a consistent structure. Most datasheets are divided into five sections:
Section | What It Contains | How Much Attention It Needs |
Generator set ratings | kW, kVA, power factor, prime/standby duty — the headline output figures | Critical — read every line |
Engine specifications | Make, model, displacement, aspiration, fuel consumption, cooling type | Critical — read and verify |
Alternator specifications | Make, model, voltage regulation, THD, insulation class, IP rating, subtransient reactance | Important — several hidden traps here |
Electrical output data | Voltage, frequency, phase, current at rated load, short circuit capability | Important — confirm matches your site |
Performance conditions | Ambient temperature, altitude, reference standard — the conditions at which all ratings apply | Critical — often overlooked; changes everything |
Mechanical data | Dimensions, weight, noise level, exhaust specifications, fuel tank capacity | Review for installation planning |
Options and accessories | ATS, remote monitoring, paralleling kit, extended fuel tank, weather canopy | Review for completeness of supply |
Standby Power (ESP) — kW and kVA
What it means: The maximum output the generator can deliver during a utility power outage. Defined by ISO 8528 as a maximum of 200 hours per year at variable load with an average load factor not exceeding 70%. This is the highest number on the datasheet — it is also the one that applies to the narrowest range of applications.
What to look for: Standby rating is appropriate only for true backup applications: a building that has reliable grid power 95%+ of the time and uses the generator only for occasional outages. If your generator will run more than 500 hours per year, standby rating is not the correct figure to size against.
⚠ Red flag: If a supplier quotes only the standby rating for a prime power application (a site running on generator as primary power source), the generator will be undersized. Ask specifically: 'What is the prime power rating?' If they cannot answer, ask for the ISO 8528 prime power figure.
Prime Power (PRP) — kW and kVA
What it means: The maximum output the generator can deliver continuously at variable load for an unlimited number of annual hours. Defined by ISO 8528. Prime rating is typically 80–90% of standby rating on the same engine.
What to look for: For any application where the generator is the primary power source — off-grid sites, frequent or extended outages, telecom towers, construction sites, remote facilities — prime rating is the correct figure. Verify that the prime rating appears on the datasheet, not just the standby figure.
⚠ Red flag: A datasheet that lists only kVA without specifying prime or standby duty is incomplete. Do not order based on an unclassified output figure — ask the supplier to confirm which duty rating applies.
Power Factor (pf)
What it means: The ratio of real power (kW) to apparent power (kVA). Almost all generator datasheets rate output at 0.8 power factor lagging. This means a 100 kVA generator delivers 80 kW of real power.
What to look for: Confirm the power factor at which the rating is stated. If your load has a lower power factor than 0.8 (heavy inductive loads — motors, welders, variable speed drives), the generator will reach its kVA limit before its kW limit. Recalculate: required kVA = your load kW ÷ your actual power factor.
⚠ Red flag: Some datasheets state ratings at unity power factor (pf 1.0). A '100 kW at pf 1.0' generator is only 80 kW at the standard 0.8 pf rating. This is not fraud — it is a legitimate test condition — but it means the generator is smaller than a buyer assuming 0.8 pf would expect.
Quick check: find the kW and kVA figures on the datasheet. Divide kW by kVA. The result should be approximately 0.8 (for a standard 0.8 pf rating). If the ratio is 0.9 or higher, the datasheet may be rating at unity power factor — verify with the supplier.
Engine Make and Model
What it means: The engine brand (Cummins, Perkins, Volvo Penta, etc.) and the specific engine family model number.
What to look for: Cross-reference the model number against the engine manufacturer's own datasheet. The engine manufacturer publishes independent specifications for each model — including rated output, fuel consumption, and service intervals. Verify that the generator manufacturer's claimed output is within the engine manufacturer's published rating for that model.
⚠ Red flag: If the engine model number on the generator datasheet does not match any model in the engine manufacturer's published catalogue, the specification may be fabricated. Request the engine's own data sheet directly from the supplier and verify independently at the engine manufacturer's website.
Displacement and Aspiration (Turbocharged / Naturally Aspirated)
What it means: Displacement is the total swept volume of the engine's cylinders in litres. Aspiration describes how air is delivered to the cylinders: naturally aspirated (air drawn in by piston motion alone) or turbocharged (air forced in by a turbocharger driven by exhaust gases).
What to look for: Turbocharged engines produce more power per litre of displacement and perform significantly better at altitude. For any site above 1,000m, turbocharged engines are strongly preferred. Naturally aspirated engines lose approximately 3% output per 300m altitude gain; turbocharged engines lose approximately 1–1.5% per 100m.
⚠ Red flag: A naturally aspirated engine specified for a high-altitude site (above 1,500m) will be significantly underrated in service. Confirm turbocharged aspiration for any elevated location.
Fuel Consumption (L/hr or g/kWh)
What it means: Fuel consumption is stated either as litres per hour (L/hr) at a specific load (usually 100% and 75% of rated output) or as specific fuel consumption in grams of fuel per kilowatt-hour of energy produced (g/kWh). Specific fuel consumption (SFC) allows direct comparison between engines of different sizes — lower is more efficient.
What to look for: For a 100 kW generator, expect approximately 22–28 L/hr at full load (diesel density ~0.835 kg/L). In g/kWh terms, a well-tuned modern turbocharged diesel engine should achieve 195–215 g/kWh at rated load. Values above 230 g/kWh indicate an older or less efficient design.
⚠ Red flag: Fuel consumption figures stated without specifying the load level are meaningless. '20 L/hr' fuel consumption for a 100 kW generator could mean full load (acceptable) or 50% load (indicating poor part-load efficiency). Always check the load level at which the fuel consumption figure is stated.
Cooling System
What it means: Describes how the engine manages heat: radiator-cooled (air blast through a built-in radiator) or remote radiator (radiator mounted separately, connected by coolant hoses). Most generator datasheets also specify the maximum ambient temperature the cooling system is rated for.
What to look for: Confirm the rated ambient temperature of the cooling system against your site's maximum ambient temperature. Standard ratings are 25°C, 40°C, or 45°C. Sites in tropical Africa or the Middle East regularly reach 40–48°C. If the datasheet cooling rating is 40°C and your site regularly reaches 48°C, the generator will overheat.
⚠ Red flag: A datasheet that specifies cooling system capacity only at 25°C ambient is not useful for tropical or desert installations. Request confirmation of rated output and cooling performance at 40°C or 45°C ambient.
The alternator section is the most technically dense part of the datasheet and the one most commonly skipped by buyers who are not engineers. It contains several figures that directly affect how the generator performs with your specific load — and one figure that is frequently used by less reputable suppliers to misrepresent motor starting capability.
Alternator Make and Model
What it means: The alternator manufacturer (Stamford, Leroy Somer, Mecc Alte, or Chinese OEM) and model number.
What to look for: Cross-reference the model number against the alternator manufacturer's own datasheet. A Stamford PI274E and a Chinese OEM alternator with a model number that looks similar are not the same product. The alternator manufacturer's website lists every genuine model — verify that the stated model exists.
⚠ Red flag: 'Stamford-type' or 'Leroy Somer-equivalent' language on a datasheet means the alternator is not a genuine Stamford or Leroy Somer product. It is a Chinese copy of unknown quality. If genuine brand is specified in your purchase order, ensure the quotation and order acknowledgement confirm the genuine OEM — not an equivalent.
Voltage Regulation (±%)
What it means: The maximum deviation of output voltage from the nominal set point under steady-state load conditions. A figure of ±1% means the output voltage will stay within 1% of the target voltage (e.g. 380V ± 3.8V) under all load conditions from no-load to full load.
What to look for: Commercial and industrial applications: specify ±1% or better. This requires an electronic AVR (Automatic Voltage Regulator). Avoid generators specifying only ±2.5% or ±5% — these indicate older shunt-excitation alternators with less precise regulation, which can cause problems with sensitive electronic equipment.
⚠ Red flag: A datasheet that does not state voltage regulation at all is a significant omission. All reputable alternator manufacturers publish this figure. Its absence suggests either a low-quality alternator or a datasheet assembled without reference to actual tested specifications.
Total Harmonic Distortion — THD or THDv (%)
What it means: The percentage of the output voltage waveform that consists of harmonic frequencies (multiples of the fundamental 50/60 Hz). Lower THD means cleaner, more sinusoidal power.
What to look for: For office, commercial, and light industrial loads: THD below 5% at full resistive load is standard. For data centres, hospitals, and sensitive electronics: request THD below 5% at full non-linear load — a harder requirement that depends on the alternator's subtransient reactance.
⚠ Red flag: THD stated at 'full resistive load' is a best-case figure. Non-linear loads (UPS systems, variable speed drives, computers, server power supplies) produce significantly higher THD. If your load is predominantly non-linear, ask for THD test data at non-linear load — not just at resistive load.
Subtransient Reactance X''d (per unit)
What it means: The subtransient reactance determines how much the alternator's output voltage drops when a large motor starts. A lower X''d means less voltage dip during motor starting.
What to look for: Standard commercial alternators: X''d of 0.14–0.20 pu. For sites with large motors (above 30% of generator kVA rating): specify X''d of 0.12 or lower. For data centres and hospitals: X''d of 0.10–0.12. This is a physical characteristic of the alternator winding design — it cannot be changed after manufacture.
⚠ Red flag: Many datasheets omit X''d entirely. If your application includes large motor starting — HVAC compressors, pumps, industrial motors — request X''d from the alternator manufacturer's datasheet. A supplier who cannot provide this figure does not understand the alternator they are selling.
Insulation Class
What it means: The thermal classification of the alternator winding insulation. Class H insulation is rated to 180°C — the industry standard for generator alternators. Class F is rated to 155°C.
What to look for: Always specify Class H insulation. At continuous full load in tropical ambient temperatures, alternator winding temperatures can exceed 130°C. Class H provides adequate thermal margin. Class F does not in high-ambient installations.
⚠ Red flag: Class F insulation specified for a tropical installation is a service life concern. The alternator will meet its rated output initially but insulation degradation will be accelerated. Insist on Class H.
Every power rating on a generator datasheet is valid only at a specified set of ambient conditions. These conditions are stated in the 'reference conditions' or 'performance conditions' section — sometimes in small print at the bottom of the datasheet. They are the most important footnote in the document.
Reference Condition | Standard Value | Real-World Implication |
Ambient temperature | 25°C or 40°C | Output falls by approximately 1% per 5°C above |
Altitude | Sea level (100 kPa / 1,000 mbar) | Output falls approximately 1–1.5% per 100m |
Relative humidity | 30% or 60% | High humidity reduces air density and |
Reference standard | ISO 8528, BS 5514, | Confirm ISO 8528 — the international standard |
⚠ The Altitude + Temperature Combination Is Cumulative
Buyers often account for altitude or temperature derating separately — but not both together. A site at 2,500m altitude and 42°C ambient applies both corrections simultaneously. A generator rated 500 kW at sea level / 25°C may deliver as little as 370–400 kW at that site — a 20–25% reduction. Always ask your supplier for the combined altitude-and-temperature derating figure for your specific site conditions. Reputable suppliers provide this calculation with every quotation.
Noise Level — dB(A) at 1 Metre or 7 Metres
What it means: The sound pressure level produced by the generator set, measured at a specified distance. Standards vary: some manufacturers measure at 1 metre, others at 7 metres. These figures are not directly comparable without knowing the measurement distance.
What to look for: Always confirm the measurement distance. A figure of '75 dB(A)' means very different things at 1 metre versus 7 metres. Convert to a common reference: for an outdoor point source, noise falls by approximately 6 dB(A) for every doubling of distance.
⚠ Red flag: A datasheet stating 'low noise' without a specific dB(A) figure and measurement distance is not a specification — it is marketing. Require a measured dB(A) value at a stated distance before accepting a noise claim.
Dimensions and Weight
What it means: Overall length, width, and height of the generator set in its standard configuration. Dry weight (without fuel) and wet weight (with full fuel, oil, and coolant).
What to look for: Verify that the generator fits through all access points on its route to the installation location — doors, corridors, lift lobbies. Confirm the floor loading capacity of the installation room against the wet weight. For canopy-mounted units, check that forklift or crane access is available for the weight stated.
⚠ Red flag: Weight listed as 'approximate' without a measured figure is a concern for installation planning. Request a confirmed weight from the factory — generator weights vary significantly between configurations with different fuel tanks and canopy types.
1 Using the Standby Rating for a Prime Power Application
The standby rating is always the largest number on the datasheet. Buyers who size against it for a prime power application will have a generator running beyond its prime power limit. This accelerates engine wear, shortens overhaul intervals, and voids the warranty.
2 Comparing Generators from Different Suppliers Using Different Units
Supplier A quotes 200 kW, Supplier B quotes 250 kVA. At 0.8 pf, these are the same generator. Buyers who assume 250 > 200 and choose Supplier B based on that comparison are not comparing anything meaningful. Convert all quotes to kW at your actual power factor before comparing.
3 Ignoring Altitude and Temperature Derating
The most expensive mistake in generator procurement. A buyer in Nairobi (1,800m, 38°C summer ambient) who sizes a generator based on sea-level / 25°C nameplate ratings will receive a unit delivering approximately 85–88 kW for every 100 kW of nameplate — 12–15% short. At 200 kW total load, that is 25–30 kW of unmet demand. Always apply site derating before finalising size.
4 Accepting "Stamford-Type" as Genuine Stamford
A 'Stamford-type' or 'Stamford-equivalent' alternator is not a Stamford alternator. It is a copy of unknown quality, produced by any one of dozens of Chinese alternator manufacturers. If your specification requires Stamford, your purchase order must say 'Stamford — genuine OEM only' and request the alternator serial number traceable to Stamford's production database.
5 Not Checking Fuel Consumption at Partial Load
Most generators operate at 50–80% of rated load in real installations. A generator with excellent fuel consumption at 100% load may be significantly less efficient at 60% load — particularly if it is an older naturally aspirated design. Request fuel consumption figures at 100%, 75%, and 50% load before finalising selection for a prime power application.
6 Treating the Datasheet as the Whole Specification
A datasheet is a marketing document as well as a technical document. Reputable suppliers back the datasheet with a factory test certificate that shows measured performance on the specific unit you are purchasing. Always request a factory load bank test certificate — not just the standard datasheet. The test certificate shows actual voltage, frequency, power output, and fuel consumption measured on your generator before shipment.
# | Question | Why It Matters |
1 | Is the rating prime (PRP) or standby (ESP)? | Wrong duty rating = undersized or overpaying for oversize |
2 | At what power factor is the kVA rating stated? | Rating at pf 1.0 delivers only 80% of that in kW at standard 0.8 pf |
3 | Does the engine model number appear in the engine | Fabricated model numbers indicate a specification document, not a real product |
4 | Is the fuel consumption stated at full load or partial load? | Full load fuel consumption is best-case; real-world will differ |
5 | What is the rated ambient temperature for the cooling system? | Standard 25°C rating is inadequate for tropical sites |
6 | What altitude is the rating stated at? | Sea-level rating must be derated for elevated sites |
7 | Is the alternator genuine OEM (Stamford / Leroy Somer) or "type"? | "Type" means a copy — request confirmation and serial number |
8 | What is the voltage regulation figure (±%)? | Anything above ±2.5% is inadequate for commercial loads |
9 | What is the subtransient reactance (X''d)? | Required for motor starting calculation; often omitted |
10 | What is the alternator insulation class? | Class H mandatory for tropical and continuous-operation sites |
11 | What is the noise level — dB(A) at what distance? | Distance must be stated; 1m and 7m figures are not comparable |
12 | Is a factory load bank test certificate included? | Test certificate confirms actual measured performance on your unit |
We publish separate datasheets for every generator model in our range, each specifying both prime and standby ratings, the engine manufacturer's model number, the alternator manufacturer's model number, the performance conditions (ambient temperature and altitude), and fuel consumption at 100% and 75% load.
✔ What our datasheets include as standard
Prime power (PRP) and standby power (ESP) ratings — both stated per ISO 8528. Engine make and model — cross-referenceable against Cummins, Perkins, Volvo Penta, or Baudouin published catalogues. Alternator make and model — genuine Stamford or Leroy Somer as standard on export specification. Voltage regulation: ±1% (electronic AVR). Insulation class: H. Fuel consumption at 100% and 75% load. Noise level in dB(A) at 1 metre and 7 metres. Performance conditions: ambient temperature and altitude clearly stated. Factory load bank test certificate — provided for every unit before shipment.
If you are reviewing a competing quotation alongside ours and want a field-by-field comparison, send us the competitor's datasheet. We will identify every specification difference and explain what each one means in practice for your application. We respond within 24 hours.
· Request a datasheet for any Leading Power model — available by email within 2 hours
· Request site-specific derating calculation — altitude and temperature corrections provided with every quotation
· Request alternator serial number traceability — Stamford and Leroy Somer OEM confirmed on all export units
· Factory load bank test certificate — included with every shipment, not optional
Leading Power is a CE-certified diesel generator manufacturer based in Fu'an, Fujian, China. Established in 2008, supplying 5kW–3,000kW generator sets to buyers in 60+ countries. Full technical documentation — datasheets, test certificates, altitude derating calculations — available for all models. 24-hour response.
