Altitude is a site condition that should be included in equipment selection. The effect on available performance depends on the proposed engine, alternator and cooling arrangement. Provide the actual installation elevation and obtain the applicable manufacturer information instead of applying an unexplained universal percentage.
Review altitude with the other site conditions
Elevation should not be assessed independently of ambient conditions and installation design. The equipment package may have several performance constraints that need to be considered together. Record which published rating or correction basis is being used and whether it applies to the complete proposed configuration.
Correct model
The factor must come from the actual manufacturer/model data for the relevant conditions.
Inputs
Altitude is not a percentage to guess. It is an operating condition to verify against the actual generator.
Check the relevant component rating
Engine output and generator-set capability are not interchangeable catalogue figures. Match the manufacturer’s site-condition basis to the selected equipment before confirming the available site rating.
Keep the adjusted selection traceable
Retain the site inputs and supporting equipment data with the capacity assessment. If the installation location or package changes, revisit the review. A catalogue headline rating without its reference conditions is not sufficient evidence of the capacity available at the final site.
Start Engineering Review
Start Engineering Review. Share the application, location and information available so the next discussion can address your actual requirement.
Related guidance
Engineering intent
Altitude Derating should be evaluated as part of the complete power system rather than as an isolated catalogue item. Operating duty, connected load, interfaces, protection, controls, installation conditions, testing requirements and lifecycle consequences determine whether the arrangement is appropriate.
Engineering considerations
Transformer energisation can become the hardest transient even when normal downstream load is moderate. Generator capability depends on where and how it operates. These conditions can affect equipment configuration and manufacturer-rated performance. Current manufacturer data for the exact generator/engine configuration. Do not assume one universal derating percentage across all models. Best where a properly engineered generator room is available. Selection depends on the installation—not merely appearance. Do not select equipment based on a generic: Acoustic performance should be verified for the actual generator and installation. For packaged systems, verify the enclosure/container’s thermal performance. A generator that cannot reject heat cannot deliver its electrical rating reliably.
Selection and design considerations
That may be a subset of the complete facility. For extended generator operation, the loading profile becomes especially important. A generator intended for long-duration operation should be selected from actual model/rating data for the intended duty. Do not add large arbitrary spare margins for hypothetical growth. Long-term light loading may be undesirable for certain diesel engines and operating profiles. Actual acceptable minimum loading and corrective practices should follow: Do not assume one universal minimum-load percentage across every engine family. Use actual manufacturer derating/performance data for the selected configuration where applicable. Reduced air density at altitude can influence combustion, cooling and overall generator capability.
Integration and protection considerations
| A lower power factor means the generator must supply more apparent power for the same useful kW. | Generator rating |
|---|---|
| Typical real-power equivalent at 0.8 PF | Final available kW depends on generator rating, duty, PF capability, ambient conditions, altitude, cooling, engine/alternator combination and manufacturer data. Trigger this warning if PF is below 0.8: Generator, alternator, cable, switchgear and power-quality review may be required. Trigger stronger warning if PF is below 0.7: Do not finalise generator kVA without engineering review. Trigger this warning when customer selects motors, pumps, compressors, lifts, chillers, cranes or conveyors: Motor loads may require higher starting kVA than running kVA. Trigger this warning when customer selects UPS, server room, data centre, medical load, CCTV, access control, bank systems, telecom, BMS, PLC or lab instruments: |
Testing, commissioning and verification
This tool provides preliminary fuel-cost and energy-performance estimation only. Actual fuel cost per kWh depends on generator model, load percentage, engine condition, maintenance quality, fuel quality, ambient conditions, site derating, operating strategy, duty, measurement accuracy and fuel price. Final operating-cost evaluation requires load data, fuel data, service condition Do not use this tool to promise fuel savings. This tells how fast fuel is being used. This tells fuel used per useful unit of electricity. This tells approximate fuel cost per electrical unit.
| Generator A | 20 L/h |
|---|---|
| 80 kW | 80 kWh per hour |
| Generator B | 15 L/h |
| 30 kW | 30 kWh per hour |
But it may be producing far less useful power.
Operating and lifecycle considerations
IT/server load
| Usually UPS-linked; review UPS input data | Mixed building load |
|---|---|
| Use measured PF or conservative estimate | Final selection should use actual load schedule and measured data where available. It represents real working power — the useful power consumed by loads such as: For generator sizing, kW is essential, but it is not enough by itself. It represents apparent power — the total electrical capacity that the generator/alternator must support. 100 kVA / 80 kW at 0.8 PF So the generator can support 80 kW real power at 0.8 power factor, subject to rating, duty, derating and manufacturer conditions. Power factor describes how effectively apparent power becomes useful work. |
Decision and application considerations
Avoid clutter, excessive colors, weak stock imagery and unreadable small print. diesel generator, generator rental, DG service, generator AMC, ATS AMF, load bank testing, generator sizing, Hyderabad It is a downloadable overview of Reddy Generators’ generator sales, rental, service, installation, testing, AMC and support capabilities, subject to technical verification and written quotation. Can I use the checklist to get a generator quote? Yes. The checklist helps collect load, site, voltage, phase, runtime, fuel, ATS/AMF and service details so the enquiry can be reviewed more accurately. Does the load schedule template give final generator size? No. It helps collect load data. Final generator sizing requires engineering review, motor-starting analysis, UPS review, fuel runtime, derating and site conditions.
Direct answer
Altitude is a site condition that should be included in equipment selection. The effect on available performance depends on the proposed engine, alternator and cooling arrangement.
The practical decision for Altitude Derating should be based on verified load, equipment, interface and site information. Where equipment-specific data, regulatory applicability or a project study is required, this guidance does not replace that verification.