Power, load and generators
A barn was wired to light a space and run a few tools. A wedding asks it to run a kitchen, a band and a climate system at the same time.
Electricity is the constraint that decides more of a barn wedding than anything except alcohol, and it is almost never discussed on a tour. The building looks powered because the lights come on. Whether it can carry a full event is a different question, and the answer is arithmetic rather than opinion.
What a barn was wired for
Agricultural buildings are wired for the job they were built to do: overhead lighting, a few outlets, sometimes a well pump or a fan. Conversions add circuits, but they rarely add service capacity, because upgrading the incoming supply on a rural property means involving the utility and paying for a run of line across a field. So the sockets multiply while the ceiling stays where it was.
The number that matters is the size of the main service, not the number of outlets. Ask the venue what the service is rated at, whether the panel has spare breakers, and whether anything else on the property shares that supply — a farmhouse, a well, a cold store. A shared supply means your event competes with a refrigeration compressor that cycles on without warning.
The arithmetic of a single circuit
In the United States a general-purpose outlet is typically on a 120-volt, 20-amp circuit. Multiply the two and you get 2,400 watts of theoretical capacity, but code treats a load running more than three hours as continuous and limits it to eighty per cent, which brings the working figure closer to 1,900 watts. A 15-amp circuit is proportionally smaller.
Then look at what people plug in. Anything that makes heat is enormous: a coffee urn, a warming cabinet, a fryer, a portable heater. Anything that makes cold is nearly as bad, and it has a surge on start-up that a small generator will trip over. Lighting and audio are trivial by comparison, which is why the band is rarely the problem and the caterer usually is.
The practical failure is not a blackout. It is a breaker in a locked panel tripping during the first dance while nobody on site knows where the panel is. Ask who holds the key and who is authorised to reset it.
Building a load list
Do this once, four to six weeks out, and it will be the most useful hour of planning you spend.
- Ask every supplier for the wattage of every item they will plug in, and whether any of it needs a dedicated circuit.
- Add the venue's own fixed loads: lighting, restroom trailer, well pump, walk-in.
- Add heating or cooling equipment, which is usually the single largest item on the list and the one most often forgotten.
- Note the start-up surge on motors and compressors separately from their running draw.
- Send the totalled list to the venue and ask, in writing, whether the site carries it.
Suppliers answer this question willingly. They have all been burnt by it. Caterers in particular will tell you exactly what they need, because arriving to find they cannot run their warming equipment is their nightmare rather than yours.
When you need a generator
A generator becomes necessary when the load list exceeds the service, when critical equipment cannot share a circuit with anything else, or when part of the event sits away from the building — a tent in a field, a ceremony at the tree line, a bar under canvas. It also becomes necessary when a venue's answer to the power question is vague, because vagueness on a load question generally means nobody has measured it.
Size the machine to the running load plus headroom for surge, not to the running load alone. A generator sized exactly to the arithmetic will hold until a compressor starts. Rental companies size this for you if you give them the list, which is another reason to build the list.
Fuel, noise and placement
A generator is a machine that burns fuel and makes noise for the length of your event, and where it sits is a real decision.
Placement has to satisfy three things at once: far enough from guests that conversation works, far enough from the building that exhaust does not draw in through a door or window, and close enough that the cable run is manageable. Cable across a guest route needs matting, and matting needs to be part of the quote.
Diesel machines in acoustic housings are markedly quieter than open-frame petrol units, and the difference is audible in the ceremony. If the ceremony is outdoors and quiet matters, ask whether the generator can be shut down for that twenty minutes and what is running off it — because if the sound system is on the generator, it cannot be.
Fuel is the other half. Ask how many hours the tank runs at your expected load, who refuels, and whether refuelling during the event is planned or improvised. Running dry at eleven at night, in a field, is a genuinely bad way to end a party.
Distribution and safety
The generator is the source. Getting power from it to twelve places around a site is a separate job, and it is where amateur set-ups go wrong. You want proper distribution boxes with residual current protection, outdoor-rated cable, and connections kept off wet ground. In a working farm setting the ground is wet more often than not.
If the venue supplies its own generator, ask when it was last serviced and load-tested. A machine that has sat under a tarpaulin since last October is not a plan.
The three questions
Take these to the tour, alongside the rest of the questions list:
- What is the electrical service rated at, and what else shares it?
- Has any event here needed a generator, and for what?
- Who is on site during the event who can find and reset the panel?
The third one is the tell. A venue that can name that person runs events properly. A venue that cannot has never had to.
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