Natural gas and diesel generators should be compared using your site’s fuel supply, operating duty and load requirements. Neither fuel is the best choice for every project. Request model-specific data and quotations for the same rating and scope of supply.
Updated 13 October 2026.
Natural gas vs diesel: what should you compare?
| Project question | Natural gas generator | Diesel generator |
|---|---|---|
| Fuel plan | Confirm gas flow, pressure and supply availability. | Confirm fuel storage, quality and refilling arrangements. |
| Operating duty | Confirm the exact standby, prime or continuous rating. | Confirm the exact standby, prime or continuous rating. |
| Installed cost | Include gas connection and any required conditioning. | Include tank, fuel management and delivery costs. |
| Evidence to request | Model-specific consumption, emissions and sound data. | Model-specific consumption, emissions and sound data. |
Start with fuel supply and operating duty
For natural gas, confirm the available flow and pressure against the proposed engine requirements, and discuss supply availability during the events you expect the generator to cover. For diesel, plan on-site fuel storage, fuel quality management and refilling. These are project decisions to settle before comparing generator prices. See the Cummins application manual, fuel selection section.
Standby, prime and continuous ratings describe different operating duties. Compare proposals with the same rating and ask for output at your actual site conditions. Main loads and motor-starting requirements also matter. The Cummins generator-set selection guide explains why ratings, site conditions and load behavior belong in a sizing review.
Compare efficiency and total project cost
Use fuel-consumption data for the exact configuration at comparable loads. If a proposal includes combined heat and power (CHP), identify whether its efficiency figure measures electricity alone or electricity plus useful recovered heat. Those figures have different meanings. The EPA guide to CHP efficiency explains the distinction.
For a fair commercial comparison, ask each supplier to itemize the generator set, fuel infrastructure, transfer controls, enclosure, transport and commissioning. Then request an operating-cost estimate using your local fuel prices, expected loads, operating hours and service costs. A purchase-price comparison alone cannot tell you which proposal suits your project budget.
Check emissions, noise and maintenance data
Natural gas combustion is not emission-free. Engine design, tuning and exhaust treatment affect different pollutants. Ask for configuration-specific emissions data and the applicable project documentation instead of assuming one fuel is always cleaner. The EPA reciprocating-engine technology catalog describes these trade-offs.
For noise, compare sound data with the same measurement distance, load and enclosure conditions. The engine, exhaust, cooling fan and installation all contribute to the result. See the noise sections of the Cummins application manual.
For maintenance, request the exact engine service schedule and a parts-and-labor estimate. Engine size, speed and configuration influence maintenance requirements, as discussed in the EPA engine catalog. Plan service access and downtime for the proposed installation.
Questions to answer before requesting a quotation
- Electrical requirements: required power, voltage, frequency, phase and a list of the main loads.
- Operating plan: backup or regular operation, expected hours and load changes.
- Fuel information: gas analysis and supply pressure, or diesel storage and refilling arrangements.
- Site information: destination country, installation location, altitude, temperature and enclosure requirements.
- Documents to request: exact engine and alternator models, rated output, consumption data, service schedule and scope of supply.
Frequently asked questions
Which fuel is cheaper to run?
There is no universal answer. Combine consumption at your expected load with local fuel prices, operating hours and model-specific service costs. Ask for estimates based on the same electrical output and operating duty.
Can a piped natural gas supply guarantee unlimited running?
No. A fuel connection does not change the generator’s approved operating rating. Check its duty limits and planned service stops, as well as the availability of the gas supply.
Can I compare CHP efficiency directly with electrical efficiency?
No. Total CHP efficiency includes useful recovered heat as well as electricity. Compare electrical efficiency on the same fuel-energy basis, and assess useful heat separately.
Can a natural gas generator also use biogas?
Only after confirming a suitable configuration. Gas composition, heating value and contaminants affect suitability. Share a gas analysis and request confirmation of any conditioning and output limitations for the proposed engine.
Discuss your generator project with Junwei Machinery
Browse our gas generator listings and diesel generator listings. You can start with the 80 kW natural gas and biogas generator or 100 kW diesel generator listing, then request the documents for your required configuration.
Contact Junwei Machinery with the project information above to discuss a quotation. Use the linked technical references as background and request current model documents for the proposed generator set.
