Get your calculator out – it’s time for a maths lesson!
By Mark Powell
Electrics.
Possibly the most expensive single item on an exhibition stand, and the most contentious. At the time of writing (2024) we have recently paid over £1,000 for a single 1kW socket. Which is why working out what power you actually need, so that you don’t order too much, is so important.
The basics.
Working out your power requirements is simple if you know three basic things:
- 1,000 watts = 1kW (kilowatt).
- 1kw = 4A (amps)
- Amps x Volts = Watts
First off, we need to define whether we are totting up our power requirements in watts (W) or kilowatts (kW). Mix the two up and your figures will either be very low or very high!
Low power items using under 1kW, such as screens, fridges and lights, are usually rated in watts. Let’s say you have a stand with two 43” screens at 100W each, a domestic fridge using 200W and ten 20W lights. That gives you the following:
- Screens: 2 x 100W = 200W
- Fridge: 200W
- Lights: 10 x 20W = 200W
Total power consumption: 200 + 200 + 200 = 600w.
As power at UK venues is generally sold by the kilowatt (we’ll cover the other option later) I always convert my final figure to kW to make the final sums easier. So with 1,000W = 1kW, 600 watts gives you 0.6kW.
How do I know what the thing uses?
Working out what an item uses power-wise is usually very easy. Most items will have a sticker, or a printed bit in relief (a ‘legend plate’), that gives you all the information on the item, including the wattage that the item uses.
Sometimes the usage is given in amps. If this is the case, using Amps x Volts = Watts you can work out the power usage in watts. In the UK, mains electricity is 240 volts. If an item is rated at 1.2 amps for instance, the sum will be 1.2 amps x 240 volts = 288 watts.
Don’t get con-fused!
I’ve lost count of the times that I’ve asked a client how much power something like a coffee machine takes, only to be given the answer “13 amps – it says so on the plug”. Yes, it does say ’13 amps’ on the plug, but that’s not the power rating of the item; that is the rating of the fuse in the plug, which is there to protect the item in the event of a power surge. The plug fuse is not the power usage. Go and check the legend plate!
Socket options.
If you are ordering sockets – which is the most common way of ordering power at UK venues – they will be rated, and charged, according to the power supplied to them. You should have the following options:
- 500W / 2 Amp
- 1kW / 4 Amp
- 2 kW / 8 Amp
- 3 kW / 12 Amp
For our example above we will need to order a 1kW socket to have enough power for our 0.6kW of appliances. If you were tempted to order a 500W socket to save money and hope it doesn’t trip the fuseboard with everything on, then be prepared to have to upgrade your supply on site. This can be an even more expensive pastime, with on site surcharges of at least 20% being the norm.
Always draw a plan.
To work out a more complex or larger stand than our first example, it’s best to draw a plan of the stand, on which you can mark on the power requirements for each and every item. Doing so will allow you to see where items can be grouped together to save sockets and therefore money.
For instance, if you have one wall on your stand with three screens drawing 100W each and half a dozen 20W lights to the top of the wall, then that area can all run off one 500W socket as the total power draw would be 420W. Contrary to what some electrical contractors will suggest, you do not need one 500W socket for each TV screen.
One thing to note here is that you are strongly advised by the official electrical contractors not to ‘daisy-chain’ extension leads – that is plug one into another then into another and so on. They also do not like you using extension leads on any circuit above 1kW for ‘safety reasons’, even though most UK extension leads are fused at 10 Amps. I personally do not see an issue with doing either, as long as the overall rating does not exceed the loading for the socket and all extension leads are in good working order and positioned where they will not be knocked during use.
Daisy-chain extensions at your own risk though! Although there is an alternative that we use that is perfectly compliant with all regulations and can be used for any supply up to 5kW / 20 Amps, and that is Wieland push-fit connectors and distribution blocks. I won’t go in to them here, but they can be sourced and purchased online. If you’re doing a lot of your own shows, with a lot of electrical requirements, these would be a good investment.
Amps or kilowatts?
Some venues and shows will list the socket options in amps instead of kilowatts. That’s when you need to know that each amp is 250 watts (it’s actually 240W, as Amps x Volts = Watts, and the UK mains voltage is 240V, but if you round it up to 250 it makes the sums so much easier!)
Potentially more confusing still is the trend that has appeared over the last couple of years whereby you order sockets at a ‘flat rate’ and then have to order a mains supply to those sockets. Sockets will usually be listed in kW, but mains supplies in amps. Some online ordering systems will work out the mains supply for you, but some expect you to calculate it.
Having read this far, that should be a piece of cake, with squirty cream and a cherry on top!
Let’s say you’ve calculated you need three 1kW, two 2kW and one 3kW sockets. Which mains supply do you order? They will usually have options starting at 6 Amp and going up from there.
Using our 1kW = 4 Amps rule we can calculate the mains requirement. In this example we have a total of 10kW, which is 40 Amps. The nearest two options for this would usually be 32 Amp SPN or a 50 Amp SPN. If you go for the lower option, you risk tripping your fuseboard unless you have a lot of spare capacity in your socket calculations, so you should really go for the 50 Amp SPN mains supply to be on the safe side.
Single or three phase?
SPN? I hear you say… what’s that? We have one more variable to understand: the difference between SPN and TPN. SPN stands for Single Phase Neutral (often referred to as ‘single phase’), whereas TPN is Three Phase Neutral (‘three phase’). Without getting too technical, single phase gives you 1 x your amp rating in power, where three phase gives you 3 x your amp rating. So a 10 Amp SPN gives you 10 Amps / 2.5kW, whereas a 10 Amp TPN would give you 30 Amps / 7.5kW of power.
With most small to medium exhibition stands you will be dealing with and ordering single phase. Some larger machinery requires 3 phase power, and very large stands may need 3 phase to supply enough power for the whole stand, where the phases will be split, but if you’re in either position it’s unlikely that you’ll be sorting out your own power order.
Still confused?
If the thought of ordering your own power for your exhibition stand still fills you with dread, don’t worry! Most exhibition stand builders will happily order your power for you and include the cost as part of your stand. We work out and order power regularly and have staff who can work it all out for you, including sending an installation drawing to the electrical contractor, so that all you need to do is turn up on site and plug your items in. Easy!
Deadline day.
One last thing to look out for – deadline day.
Almost every show will have a cut off date where the prices for electrics go up, usually by 20%. It used to be referred to as a late order surcharge, but in recent times the lower price is usually called an ‘early bird’ price and the higher price the ‘standard price’. Either way, you don’t want to miss the order deadline, which is usually around four weeks out from the start of the show build up. The date will be noted on the order form for the show.
