Three numbers, and only one of them is on the box
Every appliance list produces three totals and operators normally see one. The connected running watts is the sum of the nameplates: 8,880 for the default list. The design peak is what you actually expect on the meter at one instant, which at a coincidence factor of 75 percent is 6,660. The average draw is the energy divided by the hours, and for the same list it is 2,493 watts. The gap between the first and the last is a factor of three and a half, and every argument about generator size lives inside it.
Duty cycle moves one number and not the other
A fryer element at 35 percent duty is drawing 3,600 watts whenever it is drawing anything at all. Nothing about the duty cycle makes the draw smaller; it makes it less frequent. So the fryer is 40.5 percent of the connected watts and 30.3 percent of the kilowatt hours, and the water heater, at 20 percent duty over eight hours, is 16.9 percent of the peak and 9.6 percent of the energy. Meanwhile the hood fan, which is only 450 watts, runs continuously and takes 10.8 percent of the energy against 5.1 percent of the peak.
That is the whole reason the table has two share columns. The appliance to move onto propane, or onto a shore power drop when one exists, to stop the generator stalling is the one with the largest share of peak. The appliance to attack if the fuel bill is the problem is the one with the largest share of energy. On the default list those are the fryer and the fryer, but change the duty cycles a little and they separate.
Starting surge is a separate budget
The refrigeration compressor runs at 700 watts and asks for 2,100 to turn over, so it needs 1,400 watts of headroom that exists for perhaps a second. Add that to a 6,660 watt design peak and the worst instant is 8,060 watts, which fits inside the 8,750 surge rating with 690 to spare. Let every motor on the truck restart together — which is exactly what happens after a stall, or when somebody plugs the truck back in — and the same list asks 10,060 watts and is 1,310 short.
That is a sequencing problem rather than a sizing problem, and it has a sequencing answer: bring the compressors up one at a time rather than throwing the main breaker and walking away.
The load factor is the uncomfortable line
2,493 watts of average draw on a 7,000 watt machine is a load factor of 36 percent. The generator is sized for an instant and paid for by the hour, and there is no arrangement of these appliances that changes that — the peak is real and the average is real and they are four thousand watts apart. What manufacturers say about running a set lightly for long periods belongs in the manual for the set you own, and there are real differences between machine types. What is not in dispute is that you are hauling and fuelling capacity that is idle almost all day.
Questions people ask
What size generator does a food truck need?
That depends on which question you are asking, because the appliance list produces three different answers. The default list here sums to 8,880 connected running watts, expects 6,660 at one instant at a 75 percent coincidence factor, needs 8,060 for the second a compressor turns over, and averages 2,493 watts across a ten hour day. A machine has to survive the third number and will spend its life delivering the fourth. Nothing on this page is an electrical design — a licensed electrician sizes and connects the supply on a truck.
Does duty cycle reduce the generator size I need?
No. It reduces the fuel. An element at 35 percent duty draws its full nameplate every time the thermostat closes, and there is nothing stopping it closing at the same moment as everything else. Duty cycle belongs in the energy calculation, where it decides kilowatt hours and therefore fuel, and it does not belong in the peak calculation at all unless the appliances are actually interlocked so they cannot run together.
What is a coincidence factor and what should I use?
It is the share of your connected running watts that you actually see on the meter at one instant, and it is your own measurement rather than a published figure. A hundred percent is the honest setting for a truck whose thermostats are independent, because there is nothing preventing everything drawing at once. Anything lower is a bet, and the way to make it an informed one is to clamp a meter on the feed during a rush and watch what the maximum actually is.
Why does my generator stall when the running watts fit?
Because starting surge is a separate budget. A compressor that runs at 700 watts can ask for 2,100 to turn over, and that 1,400 watt difference has to come out of headroom that a running watts total never shows. On the default list the steady load fits with 340 watts to spare and the worst starting instant needs 8,060 against a 8,750 watt surge rating — fine one at a time, and 1,310 watts short if everything restarts together after a stall.
How many kilowatt hours does a food truck use in a day?
For the appliance list in the form, with each item at its own duty cycle and its own hours, it is 24.93 kilowatt hours across a ten hour run. The fryer is 7.56 of that, the griddle 5.94 and the refrigeration 4.73 between the two compressors. What that converts to in gallons of fuel depends on the machine, the load it is carrying and the manufacturer figures for it, which is why this page stops at kilowatt hours rather than guessing at a burn rate.