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What Size Generator Does a Coffee Trailer Need?

Why the usual answer is wrong

Ask what size generator a coffee trailer needs and you will get a number. The number is usually wrong, because it was produced by adding up what the equipment draws while running , and that is not what a generator has to survive.

Two things break that arithmetic. Startup draw: motors and compressors pull far more current in the moment they switch on than they use afterwards, so a refrigerator that runs at a modest load can spike several times that when the compressor kicks in. And simultaneous demand: the question is never what one appliance uses, it is what happens when the espresso machine is heating, the air conditioning is running, the fridge compressor starts and somebody switches on the grinder, all inside the same second.

The day it matters is the day you cannot afford it

Your quiet Tuesday will not find the problem. The peak lands on a hot Saturday with a queue, when the air conditioning never cycles off, the machine is recovering constantly and the refrigeration is working hardest. That is the minute the generator has to hold, and it is the minute a trailer sized on running watts trips.

The arithmetic that actually decides it

Sizing is four questions, in order:

1. What is on the trailer, and what does each item draw running? Not from memory: from the data plate on the actual unit you are buying.
2. Which of those have motors or compressors, and what is their startup draw? Air conditioning and refrigeration are the usual offenders.
3. Which of them can genuinely run at the same time? Some combinations are unavoidable. Others you can stagger by how you work.
4. What is the worst legitimate combination, with the largest startup draw landing on top of it?

That last figure is what you size to, with headroom above it. A generator running at its absolute ceiling all day is a generator with a short life.

What sets the ceiling

A fully equipped coffee trailer is typically built around a 50-amp service at 120/240 volts. A single-group espresso machine tends to sit around 20 amps and a two-group around 30, before anything else is switched on. Those two figures alone explain why coffee trailers surprise people: the machine can account for half the service before you add cooling, refrigeration and hot water.

Operators running a full setup off a generator are generally looking in the region of 12 to 15 kW rather than the portable units sold for job sites. Treat that as the neighbourhood, not as your answer. Your equipment list, your climate and how you work move it in both directions, and a number taken off a page instead of off your own load is how people end up buying twice.

The questions nobody asks until it is too late

• Where will it live? Generators are heavy, hot and loud, and the tongue of a trailer is not always the right answer.
• How loud is too loud? Many venues, markets and residential events have noise limits, and a generator that disqualifies you from bookings is an expensive mistake.
• How long will it run? Fuel capacity against a full service day, plus whether refueling mid-service is realistic.
• What happens when a venue offers power? Plenty do, and being able to take it saves fuel, noise and goodwill, but only if the trailer is wired to accept it.

Before you buy anything

Do the load arithmetic first, with the real data plates of the real equipment you intend to buy. The generator, the shore power connection and the layout around both all depend on that one number, and it is the number most people skip.

The electrical planning page covers why simultaneous demand behaves the way it does, and what goes in a coffee trailer covers the list you will be adding up.