Do I Need a Generator for My Event? Sizing It in kVA

Whether an event needs a generator comes down to one question: does the site have enough mains power, close enough to where it's needed, to run everything at once without tripping a circuit? Plenty of backyard parties get by on household power for lighting and a bluetooth speaker, but add a band or DJ rig, catering equipment, a jumping castle blower and a heater running together, and most home circuits simply aren't built for the combined load. Here's how to work out whether you need a generator, and roughly what size.

When you almost certainly need one

• The site has no mains power at all: a paddock, a beach, a bush property, or any outdoor location without a building nearby.
• The venue has power, but not enough of it. A single household circuit is commonly rated around 2.4 kW (10 amps at 240 volts) before it trips. A marquee running lighting, a PA system, catering warmers and a jumping castle blower off the same circuit will exceed that fast.
• You need power a meaningful distance from the building, since running extension leads more than a short distance drops voltage and creates a trip hazard across a guest area.
• You're running motor-driven equipment, like jumping castle blowers, fridges, coolroom compressors or an air conditioner, which briefly draw far more power at start-up than while running, and that surge is what actually trips circuits that look fine on paper.

Working out how much power you need

Add up the running wattage of everything that will be on at the same time, not everything you're hiring, since a coffee cart and a band rarely run simultaneously with a chocolate fountain and floodlighting. Typical figures for common party equipment:

• LED festoon or fairy lighting: 100-300W for a substantial run, low draw thanks to LED.
• Uplighting or a small stage lighting rig: 300-800W.
• PA system or DJ rig: 500-1,500W depending on scale; a full band with backline draws more again.
• Jumping castle blower: roughly 750W-1,500W (1-2 horsepower) per blower, and combo units with a slide often run two blowers.
• Fridge or small coolroom: 1,000-2,500W running, but with a start-up surge that can briefly be two to three times that.
• Urn or coffee machine: 2,000-2,400W, one of the single biggest individual loads at most events.
• Portable electric heater: 2,000-2,400W each, and marquees often need more than one.
• Portable air conditioner or evaporative cooler: 1,000-2,500W depending on size.

Add your running totals together, then build in headroom rather than sizing to the exact number. Motors (blowers, fridge compressors, air conditioners) draw a brief surge well above their running wattage when they start, and if that surge happens while other equipment is already drawing close to the generator's limit, it can trip the generator's own protection. A commonly used rule of thumb is to add 20-25% headroom on top of your calculated running total to absorb that surge safely, more if you're running several motor-driven items that could start at once.

Converting watts to generator size (kVA)

Generators are rated in kVA (kilovolt-amperes), not kilowatts, because real-world loads don't draw power at a perfect power factor. A commonly used conversion for standard single-phase loads is:

kVA = kW ÷ 0.8

So a calculated load of 8kW (after adding your headroom margin) needs roughly a 10kVA generator (8 ÷ 0.8 = 10). Generator hire commonly comes in set sizes, so round up to the next available size rather than down: typical hire brackets run from small 2-3.5kVA silent units for a handful of lights and a speaker, through 5-7kVA for a modest marquee setup, 10-15kVA for a mid-size wedding with catering and a band, up to 20-30kVA and trailer-mounted units for large events with heavy catering, cooling and a full production rig. If you'd rather not add it all up by hand, the generator sizing calculator lets you tick off equipment and returns a recommended kVA with headroom already built in.

Safety basics, briefly

Generators for events should be correctly earthed and protected by an RCD (safety switch); a generator is not automatically safe just because it's plugged in correctly if it isn't earthed. The applicable Australian Standard for generating sets is AS/NZS 3010, and anything beyond a single power board (multiple circuits, load calculations, transfer switching) is worth having assessed by a licensed electrician rather than worked out by guesswork. Site a generator outdoors, ventilated and well clear of the marquee, doors and windows, since exhaust carries a genuine carbon monoxide risk in an enclosed or semi-enclosed space. If you're also running a jumping castle, check its blower's power needs against your generator plan specifically, since a castle losing power mid-event needs to deflate in a controlled way, not as a surprise.

When it's part of a bigger plan

Generator needs often show up alongside other climate and comfort decisions. If heating or cooling a marquee is part of your event, size the generator against that load specifically, since heaters and coolers are some of the heaviest single draws on the list above. For a full run of what to book and when for a wedding specifically, see the wedding hire checklist.

Party Hire Near Me lists generator and power suppliers across Australia. We don't wire, earth or inspect any equipment ourselves; the figures above are general guidance to help you have an informed conversation with a supplier or an electrician, not a substitute for one. Browse power and generators for hire to compare real units and get an exact size confirmed against your site.