Most facility managers and building owners don't think about generator fuel until there's a problem — a long outage, a failed load test, or a technician standing next to an empty tank telling them the generator never had a chance to work. On-site diesel delivery solves that problem before it starts.
This guide walks you through everything: what on-site generator fueling is, how to set it up, what fuel you actually need, and how to make sure your tank is always full when it matters most.
Don't read — call. Diesel2U dispatches 24/7 for emergency generator fueling across Colorado. Call (303) 287-3835 and we'll roll a truck.
What Is On-Site Generator Fuel Delivery?
On-site fuel delivery is exactly what it sounds like: a licensed fuel hauler drives a tanker truck to your location and transfers diesel directly into your generator's fuel tank — or your on-site storage tank that feeds the generator. You never transport fuel yourself, deal with jerry cans, or make a run to a gas station with a pickup truck.
For backup generators — the kind powering hospitals, data centers, office buildings, cell towers, and construction sites — this is the standard way fuel gets replenished. The generator's tank is usually inaccessible to anything but a delivery vehicle, and the volumes required make self-service impractical anyway.
A professional fuel delivery company handles the whole thing: they bring a metered tanker, connect to your fill point, transfer the fuel, give you a signed delivery ticket showing exactly how many gallons were delivered, and leave. The whole process typically takes 20 to 45 minutes depending on tank size.
What Kind of Diesel Does a Generator Take?
This is one of the most common questions we get, so let's be direct about it.
Most commercial and standby backup generators run on dyed diesel #2 — also called off-road diesel or red diesel. It's chemically identical to the clear diesel you pump at a gas station, but it's dyed red to indicate it hasn't been taxed for on-road use. Because it bypasses the federal highway excise tax, it's typically 25 to 40 cents per gallon cheaper than pump diesel.
Tax-exempt, for generators, equipment, and off-road use. Lower cost. This is what most generators take.
Taxed for highway vehicles. Chemically identical to dyed diesel. Only required for on-road trucks.
Treated diesel that won't gel in cold temperatures. Important for Colorado winters — ask your supplier about cutoff temps.
If you're not sure which fuel your generator takes, check the manufacturer spec sheet or call us — we'll confirm the right product before we ever roll a truck.
How the Process Works, Step by Step
Getting diesel delivered to your generator is simpler than most people expect. Here's the full process from first contact to full tank:
You Contact Dispatch
Call, text, or submit a request through the app. Tell us your location, your generator's approximate tank size or how many gallons you need, and whether this is scheduled or emergency. For emergencies, always call — don't wait on a form.
We Confirm the Details
We'll confirm your delivery address, any site access requirements (gate codes, parking restrictions, overhead clearances for the truck), and the right fuel type. First-time customers usually get a quick site walkthrough call to make sure everything goes smoothly on delivery day.
A Truck Is Dispatched
We assign a certified driver and load the correct fuel. For scheduled deliveries, this happens ahead of time. For emergency calls, we roll as fast as possible — typically within a few hours in our service area.
Delivery and Transfer
The driver arrives, inspects the fill point and surrounding area for safety, connects to your tank's fill connection, and transfers the fuel using a calibrated metered pump. Every gallon is measured and recorded. The whole fill typically takes 20–45 minutes.
You Get a Delivery Ticket
Before the driver leaves, you receive a signed delivery ticket showing the gallons delivered, fuel grade, date, and driver ID. This is your compliance and accounting record — keep it. For customers using our app, it's logged automatically.
Scheduled vs. Emergency Delivery — Which Do You Need?
Most customers end up using both, for different reasons.
Scheduled (Routine) Delivery
If your generator runs regularly — for weekly load tests, construction site power, or prime power — a recurring delivery schedule keeps the tank topped off without you having to think about it. A good rule of thumb: schedule a refill when your tank hits 60–70% capacity, not when it's running low. That buffer protects you if a delivery gets delayed, and it means the generator is always ready for an unplanned outage.
Emergency Delivery
When a storm hits, a grid failure runs longer than expected, or you discover your tank is dangerously low during a critical event, emergency delivery is what keeps you running. A 24/7 dispatch service means help is available at 2am on a Sunday in January — not just during business hours. That's the whole point.
During hurricane season, severe weather watches, or any predicted extended outage event, schedule your generator fuel delivery at least 72 hours in advance. Demand spikes fast and every fuel supplier in the region gets slammed at once. Being proactive means your tank is full before competition for trucks begins.
What the Delivery Truck Needs to Access Your Site
This is where first-time customers most often run into friction. A diesel delivery truck isn't a pickup — it's a full-size tanker, and it needs room to maneuver. Here's what to have ready before your first delivery:
- A clear path to the fill point — the driver needs to get the hose from the truck to your tank's fill connection. Know where your fill cap or fill connection is located and make sure it's accessible.
- Overhead clearance — tankers are tall. If your facility has a parking garage, low canopy, or overhead obstruction near the generator, flag this upfront so we can plan the approach.
- Gate codes and security contacts — if your site requires badge access, a security escort, or has a guard gate, we need this information before arrival. An unexpected delay at a gate during an emergency outage is a bad situation.
- Spill containment — a properly designed generator installation includes a spill containment bucket or berm at the fill point. If yours doesn't have one, let us know and we'll bring absorbent material.
- The tank gauge location — your driver needs to verify fill level before and after delivery. Know where your gauge is, or have someone on-site who does.
A Note on Fuel Quality — Don't Ignore It
Here's something that surprises a lot of generator owners: diesel fuel goes bad. Stored diesel begins to degrade after 6 to 12 months. Water intrusion, microbial growth (what most people call "algae"), oxidation, and sediment buildup can all contaminate a tank that looks perfectly fine from the outside.
A generator that sits on standby for years with the same fuel in it is almost certainly running on degraded diesel — and degraded diesel clogs filters, damages injectors, and causes the generator to fail at startup. The worst possible moment to find this out is during an actual power outage.
The fix is regular fuel testing and polishing — a process that filters contaminants out of stored fuel and restores it to spec without replacing it entirely. It's far cheaper than replacing injectors or discovering your generator won't start when you need it most.
If you're not sure when your fuel was last tested, assume it needs attention. We test fuel to ASTM D-975 standards and can tell you definitively whether what's in your tank is ready to burn.
Quick Answers to Common Questions
How much does diesel delivery cost?
Fuel price is tied to the current market rate for dyed diesel #2, plus a delivery fee that varies by volume and location. Larger deliveries cost less per gallon. Emergency deliveries may carry a premium. Contact us for a current quote — pricing is transparent and itemized on every delivery ticket.
Is there a minimum delivery size?
Most providers have a minimum order — typically in the range of 100 to 300 gallons — because it's not economical to roll a full tanker for 20 gallons. If your generator has a smaller tank, talk to your supplier about options.
How long does delivery take?
Scheduled deliveries happen at the agreed time. Emergency deliveries in our Colorado service area typically arrive within a few hours of your call, depending on truck availability and distance. During major regional weather events, response times can stretch — which is exactly why proactive scheduling matters.
Do I need to be on-site during delivery?
Not necessarily. Many regular customers set up unattended delivery with gate codes and standing access instructions. For first-time deliveries, having someone on-site makes the process faster and ensures the driver can find the fill point and gauge without guessing.
What regulations apply to diesel delivery?
Diesel fuel is a hazardous material, and delivery drivers must hold appropriate HAZMAT endorsements on their CDL. The delivery equipment must be DOT-compliant. Your site's storage tank may be subject to local fire code and EPA regulations depending on its size and installation type. A reputable fuel supplier navigates all of this for you — but it's worth knowing the compliance framework exists.
Ready to set up delivery?
Tell us about your generator and we'll put together a fueling plan — scheduled fills, emergency coverage, or both. No obligation.
The Bottom Line
Getting diesel delivered to your generator is straightforward once you know the process. Find a licensed, 24/7 supplier in your area. Confirm the right fuel type for your equipment. Know your site access details. Set up a scheduled delivery so your tank stays in the 70–100% range at all times. And make sure your stored fuel is tested regularly so it's actually ready to burn when you need it.
Your generator is an insurance policy. On-site fuel delivery is what makes it pay out.