The equipment quote is only the first project expense. For long operating hours, frequent outages or long fuel-delivery distances, fuel use, low-load operation, service intervals, parts availability and downtime losses often matter more than the initial price difference.
First, Confirm Whether This Article Matches Your Project
Owners, procurement teams, facility managers and electrical leads buying a first set, expanding, replacing an old unit or adapting to a changed load profile.
It separates cost risks, comparison criteria, site inputs and engineering boundaries for procurement decisions.
A sizing basis that records operating duty, critical loads, starting sequence, environmental derating and future-expansion limits.
Compare proposals under the same duty and cost boundary. Define the load profile, expected operating hours, delivered fuel cost and maintenance conditions before comparing generator options to identify the genuinely lower-cost system.
Check 01
What Belongs in a Life-Cycle Cost Model?
Comparing only generator prices leaves tanks, transport, installation, consumables, parts and downtime risk until after delivery. Set a common cost boundary before judging differences between brands and configurations.
Include the generator, ATS, distribution, tanks and installation materials, plus fuel purchase, transport, storage and replenishment. Add scheduled maintenance, consumables, spare parts, engineering support, failure downtime, business interruption and temporary-power cost. Without written evidence, do not treat the comparison as complete.
- Generator, ATS, Distribution, Tanks and Installation Materials
- Fuel Purchase, Transport, Storage and Replenishment
- Scheduled Maintenance, Consumables, Parts and Engineering Support
- Failure Downtime, Business Interruption and Temporary Power
Check 02
Why Load Factor Changes the Fuel-Cost Assessment
The same set does not have the same cost per generated kWh at every load. Operating an oversized unit at low load can increase specific fuel consumption and create carbon buildup and maintenance problems.
Map daytime, nighttime, peak and minimum loads and distinguish routine operation from short emergency duty. Compare one set, mixed-size sets or paralleling, using reference consumption across the actual load range. Without written evidence, do not assume the selected option is economical.
- Map Daytime, Nighttime, Peak and Minimum Loads
- Distinguish Routine Operation from Short Emergency Duty
- Evaluate One Set, Mixed Sizes or Paralleling
- Compare Reference Consumption Across the Actual Load Range
Check 03
Delivered Fuel Cost Is More Than the Price per Liter
At remote or access-constrained sites and during long outages, delivery frequency, vehicle access, storage capacity and refueling windows all affect cost and reliability.
Confirm the tanker route and minimum delivery quantity and calculate turnover for day and bulk tanks. Account for rainy-season, nighttime and emergency deliveries, and set minimum level and replenishment trigger points. Without written evidence, do not treat delivered fuel cost as known.
- Confirm Tanker Route and Minimum Delivery Quantity
- Calculate Day- and Bulk-Tank Turnover
- Account for Rainy-Season, Nighttime and Emergency Deliveries
- Set Minimum Fuel Level and Replenishment Trigger
Check 04
How to Compare Different Options in One Model
Use the target service life and typical operating hours for scenario analysis instead of applying one full-load consumption figure to every duty.
Model low, medium and high annual-hour scenarios under common fuel-price, transport and maintenance assumptions. List critical-part lead times and downtime impacts, and retain sensitivity to expansion and load change. Without written evidence, do not treat the life-cycle comparison as complete.
- Model Low, Medium and High Operating-Hour Scenarios
- Use Common Fuel-Price, Transport and Maintenance Assumptions
- List Critical-Part Lead Times and Downtime Impacts
- Retain Sensitivity to Expansion and Load Changes
Decision record
Put Each Decision in the Project Record, Not Just a Verbal Confirmation
Selection should not begin with brand and price. Turn loads, duty and site constraints into reviewable project conditions, then compare supplier proposals on the same basis.
| Decision Point | Prepare on Site | Confirm in Design or Acceptance |
|---|---|---|
| What Belongs in a Life-Cycle Cost Model? | Generator, ATS, Distribution, Tanks and Installation MaterialsFuel Purchase, Transport, Storage and Replenishment | Scheduled Maintenance, Consumables, Parts and Engineering SupportFailure Downtime, Business Interruption and Temporary Power |
| Why Load Factor Changes the Fuel-Cost Assessment | Map Daytime, Nighttime, Peak and Minimum LoadsDistinguish Routine Operation from Short Emergency Duty | Evaluate One Set, Mixed Sizes or ParallelingCompare Reference Consumption Across the Actual Load Range |
| Delivered Fuel Cost Is More Than the Price per Liter | Confirm Tanker Route and Minimum Delivery QuantityCalculate Day- and Bulk-Tank Turnover | Account for Rainy-Season, Nighttime and Emergency DeliveriesSet Minimum Fuel Level and Replenishment Trigger |
| How to Compare Different Options in One Model | Model Low, Medium and High Operating-Hour ScenariosUse Common Fuel-Price, Transport and Maintenance Assumptions | List Critical-Part Lead Times and Downtime ImpactsRetain Sensitivity to Expansion and Load Changes |
Common Mistakes
These Shortcuts Leave the Risk Until After the Outage
Simply Adding Equipment Nameplate Ratings
Nameplate ratings do not show motor starting demand, coincident operation or recovery order. Capacity may look sufficient on paper yet fail to start the site loads.
Replacing Engineering Calculations with a Fixed Percentage
Reserve must separately address starting demand, environmental derating, future expansion and redundancy. One blanket percentage cannot define those boundaries.
Comparing Only the Generator-Set Price
A low purchase price is not a low total cost when fuel, distribution, installation, spares, maintenance and outage losses are excluded.
Handover Check
At Minimum, the Project Should Retain These Deliverables
End customers do not need to perform every calculation, but they should receive clear documents and know what data supports each conclusion.
Load Schedule and Starting Matrix
Record each load’s power, voltage, power factor, starting method, coincidence factor and recovery sequence.
Capacity and Rating-Basis Statement
State prime or standby duty, kW and kVA basis, environmental correction and capacity justification.
Expansion and Redundancy Limits
State whether future loads, paralleling conditions, maintenance windows and N+1 requirements have been allowed for.
Like-for-Like Proposal Comparison
Compare equipment, fuel, installation, maintenance, spares and service scope in one table.