Short answer: most food trucks need 8 kW to 12 kW of generator capacity. A coffee or dessert van can get by on 5 kW. A full-cook-line truck with electric refrigeration, a fryer, a hood fan, and lighting needs 12 kW. Sizing the generator wrong is one of the most expensive mistakes you can make on a build, and it is also one of the easiest to fix at the design stage.
Why generator size matters more than people think
The generator is the single most expensive electrical component on the truck. A Honda EU7000iS pulls about $4,500 retail. A Cummins Onan 12 kW commercial unit runs $7,000 to $9,000. Going up one size from 8 kW to 12 kW typically adds $2,500 to the build, and going down one size when you should not have saves nothing because you will be replacing it within a year.
An undersized generator will trip its breaker every time the fryer kicks back on after a refrigeration compressor cycle. An oversized generator burns more fuel than it has to and stresses smaller load components when running at low load.
How to actually size a food truck generator
You need two numbers:
- Total continuous load. Add the running watts of every electric appliance that will ever run at the same time. This is the floor.
- Peak surge load. Add the startup surge of the largest motor (compressor, hood fan, exhaust fan) to the continuous load. This is the spike the generator has to absorb.
The generator’s continuous output rating has to exceed the continuous load. The generator’s peak output rating has to exceed the surge. Most generators are rated for about 15-20 percent more peak than continuous, which is usually enough.
Real-world watt draw by appliance
| Equipment | Running watts | Surge watts |
|---|---|---|
| Standup commercial refrigerator | 700 | 2,200 |
| Standup commercial freezer | 800 | 2,400 |
| Pizza prep table | 600 | 1,800 |
| Hood exhaust fan | 800 | 2,400 |
| Make-up air fan | 600 | 1,800 |
| Espresso machine (3-group) | 3,500 | 3,800 |
| Soft-serve ice cream machine | 2,400 | 3,500 |
| Panini press | 1,800 | 1,800 |
| Microwave (commercial 1.6 kW) | 1,600 | 1,600 |
| Hot wells (3-pan) | 1,500 | 1,500 |
| LED interior lighting | 150 | 150 |
| Service window LED + sign | 200 | 200 |
| POS + receipt printer | 100 | 100 |
| Water pump (12V converter) | 100 | 300 |
Sample sizing math
Coffee/espresso truck: espresso (3500) + 2 small fridges (1400) + grinder (300) + lights (150) + POS (100) + window LED (200) = 5,650 watts continuous. Surge from compressor cycling adds maybe 1,500 above continuous. A 7 kW generator covers it. A 5 kW pushes it. We spec 7 kW for coffee builds.
Standard 16-ft cook-line truck: reach-in fridge (700) + freezer (800) + hood fan (800) + make-up air fan (600) + lighting (350) + POS (100) + water pump (100) + speed oven (1600) = 5,050 watts continuous. Surge adds another 1,500 to 2,000 with compressor and fan starts overlapping. An 8 kW generator covers it. We default to 10 kW or 12 kW because adding ice machine, panini press, or electric speed oven later is common, and a 10 kW can handle it without restating the build.
Full multi-cuisine catering truck (like the Pechanga build): reach-in (700) + freezer (800) + pizza prep (600) + hood (800) + make-up air (600) + lighting (400) + 1.6 kW microwave (1600) + 3-pan hot well (1500) + POS (100) + ice machine (1500) = 8,600 watts continuous. Surge can hit 12,000 when compressors and fans cycle in. A 12 kW generator is the right call.
Cummins, Onan, Honda, or Generac
Quality matters. A Cummins Onan QG 7000 or 12000 commercial generator is the gold standard for food trucks because it is rated for continuous duty (not just standby), runs cleaner, is quieter at the property line, and is built to log thousands of run hours. Our default for trucks 18 ft and up is the Cummins Onan 12 kW. Honda EU7000iS is also a solid choice for smaller trucks where weight matters and you can deal with the inverter limitations.
What we avoid: cheap Chinese-import 10 kW open-frame generators. The price looks right at $1,500. The compressor surge will trip them within the first three months.
Diesel or gasoline?
Diesel is more efficient (about 30 percent more BTU per gallon), runs longer between refuels, and the fuel does not go stale. The downsides: diesel generators are heavier, louder at idle, and more expensive up front. Most of our food truck builds use gasoline because the truck already has a gas chassis, fuel can be split with the engine, and noise is more easily controlled with an enclosed enclosure. Diesel makes sense for full-time catering operations running 60+ hours a week.
Where the generator goes on the truck
Outside the cook compartment, in a sound-attenuated cabinet, with cold-air intake and a tuned exhaust path. We mount most generators in a curbside cabinet between the rear axle and the bumper, with a 4-inch insulated exhaust duct exiting straight down or to the rear. The cabinet has a hinged access door for fuel and oil checks. NFPA 37 covers stationary internal combustion engine installations and gives the clearance and ventilation rules.
Quiet matters at certain venues
Wedding venues, hospitals, college campuses, downtown event sites: noise rules can require under 65 dB at 23 feet. The Cummins Onan QG 7000 is rated 67 dB at 23 ft. The Honda EU7000iS is rated 60 dB. For especially noise-sensitive venues we install a sound-attenuated enclosure with foam-lined panels that drop the rating another 5-7 dB.
Generator vs shore power
Many event venues, food truck parks, and brewery locations have 30-amp or 50-amp shore power available. The truck should be wired with a shore inlet so you can plug into venue power and shut the generator off. This saves fuel, reduces noise, and extends generator life. We install a 50-amp shore inlet with an automatic transfer switch on every build above 16 ft.
Get the size right at design time
If you tell us your equipment list (or send your menu and we will spec the equipment), we will calculate the load profile and recommend the right generator size. Get a free quote or call 719-722-2537.
Related: complete guide to starting a food truck business and recent build videos.
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We design and build custom food trucks and trailers compliant with the regulations on this page. From a single phone call to keys-in-hand in 6 to 8 weeks for most builds.
Built in Woodland Park, Colorado. Delivered to operators in CO, AZ, NE, MT, and WY.