Technical guide
How many kW of generator your event needs
Electricity is the part of the event nobody looks at until the RCD trips in the middle of the first dance. Here's how to calculate it properly and how to avoid that.
The method
Add up the loads, then leave plenty of room to spare
The calculation has three steps and none of them is complicated. First, make a list of everything that gets plugged in. Second, add up the consumption of each item. Third, add a generous margin on top and check how the load is spread across the phases.
The list is longer than people think, because hardly anyone counts what isn't theirs: sound, lighting, screen, cameras, bar, cold rooms, coffee machine, griddle, air conditioning, inflatables, ice machine and the sockets people keep asking for as the event goes on. At catered events, the kitchen usually draws considerably more than the sound.
Why it is always oversized
For three reasons, and all three are good ones. The first: inrush current. Motors, compressors and some equipment draw much more current the instant they start up than when running normally. A cold-room compressor starting up can trip a generator that was running close to its limit.
The second: diversity factor in reverse. At an event, the moments of peak consumption coincide: the bar's rush hour is also the rush hour for lighting and sound.
The third: power quality. A generator working at its limit delivers poorer voltage and frequency, and that affects electronics. In sound, this means hum and equipment going into protection and shutting down. A generator with headroom supplies more stable power.
Ballpark figures
What each block roughly consumes
Estimates to give you an idea. The real figure is on each piece of equipment's rating plate, and that is the one to use for the final calculation.
| Item | Consumption | Notes |
|---|---|---|
| Small sound system (2 speakers + desk) | Low | Can be covered by a normal domestic socket, as long as it is a stable circuit not shared with the kitchen. |
| Medium sound system (PA with subwoofers) | Medium | Needs its own circuit. It's more about the peaks than the average: bass draws power in bursts, not steadily. |
| Large sound system (line array, towers) | High | Plan it with a distribution board and load spread across phases. At this point you need to be talking to the electrician. |
| LED lighting | Low to medium | LED fixtures draw far less power than conventional lighting, but they add up with the number of units. |
| Moving heads | Medium | On top of their running consumption, they have a start-up peak when they perform their initial reset. |
| LED screen | Medium to high | It depends on the square metres and the brightness. It is one of the items that varies the most. |
| Catering and bar | High | Fridges, griddles, coffee machines and ice makers. Usually the biggest power consumer at the event. |
| Air conditioning or heating | Very high | If there is a climate-controlled marquee, it will dictate the size of the whole generator on its own. |
Rules of thumb
What you need to sort out besides the number
Keep the sound separate from the kitchen
This is the most useful recommendation in the whole article. Sharing a line with griddles, fridges and coffee machines causes voltage drops, hum in the audio and tripped breakers just as a motor starts up. If there is only one generator, at least give the sound its own outlet from the distribution board.
Balance the phases
On a three-phase generator, hanging all the sound off one phase and leaving the other two almost empty is asking for trouble. The load is spread by whoever sets up the distribution board, and it is worth asking for it explicitly.
Think about where it goes
A generator is noisy and smells of diesel. Putting it behind the stage is convenient for cabling and bad for everything else: it bleeds into the microphones and bothers the audience. Move it as far away as the cable allows, downwind and out of the line of sight. At street events, its location is also usually part of what gets authorised.
Fuel and running time
Running time depends on the tank and the load. A long event with an overnight take-down may need refuelling, and that has to be planned for: running out of diesel at three in the morning with the take-down half done is an avoidable problem.
Redundancy for critical systems
If the event is institutional or is being broadcast, it is worth arranging backup power at least for the PA system and for the streaming. A two-minute blackout at a party is an anecdote; during a broadcast, it is not.
Without a generator
When you don't need one and what the alternatives are
Venues with an adequate electrical supply
Function rooms, hotels and many haciendas have a distribution board with plenty of capacity. You just need to confirm how many amps are available at the point where you will set up, not in the building as a whole.
Small outdoor events
A ceremony, a presentation or a short event can be covered with battery-powered sound systems, with no cables and no generator.
Connecting to an existing board
Squares and municipal venues sometimes have a power hook-up for events. You need to ask for the key and confirm the contracted power before counting on it.
Reduce consumption instead of upsizing the generator
Swapping conventional lighting for LED and adjusting the screen brightness can bring total consumption down considerably and allow a smaller generator.
Two small generators instead of one large one
In some set-ups it pays off: one for the technical equipment and another for catering. Problems are isolated and you gain redundancy.
Confirm in writing who is supplying the power
At events with several suppliers, electricity is the responsibility that most often ends up with no owner until the day itself.
Keep reading
Related links
Frequently asked questions
Questions about electricity
Can I plug the sound system into a normal socket?
For small systems, yes, as long as the line is stable and not shared with the kitchen or air conditioning. Beyond a certain size you need a dedicated line or a generator.
How many kW do I need for my event?
It depends on everything that gets plugged in, not just the sound. You need to add up lighting, screen, catering and air conditioning, and allow a margin for start-up peaks. The figure comes from that list, not from a generic table.
Do you supply the generator?
Normally the organiser hires it along with the rest of the production, and we specify how much power the technical side needs and how we want the distribution board split.
Why does the sound hum when the generator is running?
It is usually an earthing problem or a result of sharing a line with equipment that introduces electrical noise. It is solved with a correct split on the distribution board and suitable cabling, not by turning the volume up.
Is the generator noisy during the event?
Yes, and you can hear it. That is why it is placed as far as possible from the audience and the microphones, within what the cabling allows.
Tell us what will be plugged in
We'll tell you how much power the technical side needs and how to split the distribution board so nothing fails.
