Why food truck builders should size electrical with their customers, not for them

Most builder–customer disputes don't start in the welding bay. They start in the electrical conversation — and they're almost all fixable with one shared spreadsheet.

Published June 15, 2026 · 6 min read

If you've been fabricating food trucks for more than a year, you've had this conversation at least twice:

Customer: "I want it to run all day, no generator, no problem."
Builder: "Okay — what equipment?"
Customer: "A flat top, two fryers, a panini press, a soft serve, and three reach-ins. Oh, and a hood. And lights."
Builder: "Okay."

That "okay" is the moment the build either becomes a calm series of decisions or becomes a fight you'll have eight months later when the soft serve trips the inverter at noon on a Saturday. We've talked to enough builders to know which conversation usually wins, and it isn't the calm one.

Here's the thing nobody likes to say out loud: most electrical disputes between food truck builders and their customers are not really about the electrical system. They're about who owns the assumptions.

Where the disputes actually live

When a build goes sideways on electrical, it almost always traces back to one of four assumption gaps:

1. Equipment that "isn't really that bad." The customer remembers their espresso machine pulls 12 amps. They forget it has a 1,600 W steam boiler that runs every six minutes.
2. Duty cycles that nobody agreed on. The customer pictures "running all day." The builder sizes for "lunch shift with a thermostat cycle." Same equipment list, half the battery.
3. Peak surge that wasn't budgeted. A 1.5 hp compressor pulls 8x its running wattage for half a second on startup. If the inverter doesn't have the surge headroom, the truck cuts out the first time both fridges kick on together.
4. The "I'll just add a generator" out. The customer says "no generator" at the kickoff and shows up at delivery asking why the truck won't run an event without one. Because no one wrote the spec down at the front.

Every one of these gaps is closable in a single 30-minute conversation. They just have to happen before you cut metal, not after.

Why "size it for them" goes wrong

Most builders we've talked to size electrical for the customer. They take the equipment list, plug it into their own spreadsheet or rely on a battery vendor's calculator, and hand the customer a number: "you need a 15 kWh pack." Done.

The customer accepts the number. Then six months later they buy a soft serve that wasn't on the list. Or they swap their convection oven for a deeper one. Or they decide to start doing 12-hour breweries instead of 4-hour lunch shifts. And the builder gets a Friday-afternoon phone call that starts with "so my system isn't keeping up…"

The builder didn't do anything wrong. The customer didn't do anything wrong. What went wrong is that the spec was never the customer's spec. They didn't see the assumptions, didn't see the duty cycle estimates, didn't see what counted as a "shift." So when reality moved, they had no way to know the spec had moved with it.

If the customer can't tell you why their system is 15 kWh and not 18, they don't own the spec. And if they don't own the spec, the next surprise is on you.

What "size it with them" looks like

The version of this conversation that works has three steps. None of them are hard. All of them get skipped under deadline pressure.

1. Build the equipment list together, in writing

Not from memory. Not from the menu. From actual nameplate ratings on actual units the customer either owns or has picked. Yes, this is annoying. Yes, it is the entire game. Half the disputes you'll ever have come from a piece of equipment that wasn't on the list when you sized the system.

2. Agree on a duty cycle, out loud

"Eight-hour service, lunch + dinner, two compressors cycling 40% of the time, fryer holding at temp 60% after warmup." That sentence should exist somewhere in writing in the build documents. If it doesn't, both of you are guessing — just at different numbers.

3. Use a neutral tool for the math

This is where we have a not-very-subtle pitch. The calculator on this site exists for exactly this conversation. The customer fills it in. You fill it in. You compare results. If you're within a few hundred watt-hours of each other, you're aligned. If you're a thousand off, you've found the dispute now instead of after delivery.

The reason we keep the tool independent — not affiliated with a battery brand, not affiliated with a builder — is so the answer doesn't carry anyone's commercial interest. If the calculator says 14 kWh, it's saying 14 kWh because of the math, not because someone gets paid more on the 18.

The handoff document

When the customer is finished with the calculator, they get a one-page spec: every device, running watts, peak surge, daily kWh, battery target, inverter target. Have them email it to you before kickoff. Look at it next to your own number. Resolve the deltas before quoting.

That spec sheet becomes a contract artifact whether you call it one or not. Six months from now, when the soft serve shows up, you can both look at the original list and see that it wasn't there. Now you're having a clean change-order conversation, not a refund conversation.

What this does for your shop

Three things, in order of importance:

• Faster kickoffs. You walk into day one with a real equipment list and a real load number. You skip the second discovery meeting.
• Fewer post-delivery surprises. Customers who own their spec are far less likely to call you in October about a system they wrote down in March.
• Cleaner change orders. When the customer adds equipment, you point at the original spec. No relitigation.

The customer wins too. They understand why their system is sized the way it is. They can plan equipment swaps without surprising you. They sound smarter at their next health inspection.

One last note on generators

This site exists because the food truck industry is moving past gas generators — for cost, noise, and increasingly, regulation. If your customer says "no generator" at the start, take that seriously and size the battery system to actually deliver. The worst possible outcome is delivering a "battery-powered" truck that needs a generator at events because the spec was too tight. That's the build that ends up on a Reddit thread.

Size for the worst day, not the average one. Document the assumptions. Hand the customer the math. The relationship gets easier from there.

More for builders: /builders · Battery vs. generator cost · Generator restrictions tracker