Written by Dakotah Merkley – Senior Vice President of Generator Source
Why Fuel Tanks Matter
When people think about generators, the focus is usually on the engine, alternator, or control system. But none of those matter without a reliable fuel supply. The fuel tank is the foundation of generator reliability.
During a recent yard walk, our operations team inspected several units and their base tanks, noting differences in design, condition, and compliance. What became clear is that fuel storage is often an overlooked vulnerability. A great generator paired with a poorly maintained tank is a recipe for failure when the grid goes down.
Understanding Base Tank Options
Base tanks are built directly into the skid of the generator, creating a compact, integrated solution. These tanks:
- Provide runtime ranging from a few hours to several days, depending on size.
- Simplify transport and installation by reducing the need for external tanks.
- Include features like fuel gauges, leak detection, and venting for safety.
The most common designs include single-wall tanks and double-wall (UL 142 or UL 2085) tanks, with the latter offering enhanced safety and compliance.
Double-Wall and UL 2085 Tanks
One of the recurring points from our yard review was the importance of UL 2085 double-wall tanks. These tanks are designed with both an inner and outer wall, providing extra protection against leaks and fire exposure.
- UL 142 Tanks: Standard double-wall protection, widely accepted in industrial settings.
- UL 2085 Tanks: Fire-rated and impact-resistant, often required for hospitals, schools, and urban projects.
For customers, the distinction matters because local ordinances, insurance providers, and bid specifications may require UL 2085 compliance. Choosing the wrong tank can mean failing inspection or facing costly retrofits.
The Risks of Neglecting Fuel Tanks
Fuel systems are one of the most common causes of generator failures, and many of those issues originate in the tank itself. Common risks include:
- Contamination: Water intrusion, microbial growth, and sediment buildup lead to clogged filters and engine stalls.
- Leaks: Single-wall tanks without secondary containment create environmental and safety hazards.
- Aging Materials: Corrosion or damaged welds reduce structural integrity.
- Regulatory Violations: Non-compliant tanks can halt projects or trigger fines.
During our yard walk, we flagged several older tanks for inspection or scrapping. Even if the generator is mechanically sound, an unreliable tank makes the system unfit for service.
Fuel Tank Sizing and Runtime Planning
One of the most practical decisions customers face is tank sizing. The size of the tank determines how long the generator can run under load before refueling.
- Small Commercial Units (20–100 kW): Often paired with tanks that provide 8–12 hours of runtime.
- Mid-Range Units (300–750 kW): Require larger integrated tanks or external tanks for 24–48 hours of operation.
- Large Industrial Units (1000+ kW): Typically supported by external tanks, but base tanks can still provide critical bridging runtime.
Lesson: Fuel tank size should be matched to both the expected outage duration and the facility’s refueling plan.
Regional Considerations: Colorado, Florida, and Texas
Fuel planning looks different depending on where a generator operates.
- Colorado: Cold weather creates risks of fuel gelling, insulated tanks and heaters may be necessary.
- Florida: Hurricanes and flooding create risks of water contamination, double-wall tanks with secure venting are a must.
- Texas: Extended heat waves and long-duration outages put greater emphasis on tank capacity and refueling contracts.
These regional factors make fuel tank decisions just as critical as generator selection itself.
When Fuel Becomes the Weak Link
In one recent inspection, our service team found a commercial property where the generator was in excellent condition, but the tank had not been filled or inspected in nearly three years. The fuel inside had degraded, creating sludge that would have clogged the system during the next outage.
The solution required draining, cleaning, and refilling, but it was a reminder that fuel management is not optional. A generator without clean, available fuel is just an idle piece of equipment.
When To Retrofit or Replace Tanks
Our operations team regularly advises customers on whether to retrofit existing tanks or replace them entirely. Factors that drive this decision include:
- Tank Age: Older single-wall tanks often don’t meet modern standards.
- Condition: Corrosion, leaks, or weak welds warrant replacement.
- Compliance Requirements: If a facility needs UL 2085 certification, upgrading may be mandatory.
- Runtime Needs: Larger loads and longer outage expectations sometimes justify external or larger tanks.
By addressing tank issues early, customers avoid emergencies and compliance delays.
Generator Source’s Approach
At Generator Source, we don’t just test the engine and alternator, we evaluate the entire system, including the fuel tanks. Our yard inspections focus on:
- Verifying compliance with UL standards.
- Inspecting for leaks, corrosion, and contamination.
- Matching tank capacity to runtime needs.
- Coordinating with customers on refueling and monitoring strategies.
This holistic approach ensures that customers are not only buying a generator but a complete, reliable power solution.
Fuel Planning Is Power Planning
Fuel tanks may not be the first thing customers think about when evaluating generators, but they are one of the most important. The right tank ensures compliance, protects against leaks, and provides the runtime a facility needs to ride through an outage.
From Colorado to Florida to Texas, our team helps customers evaluate, retrofit, and maintain fuel systems that match their power requirements and compliance needs.
Call 877-866-6895 or visit generatorsource.com to discuss generator fuel tank options and preventative service programs.