Who needs which number
Two people will ask you how much power an LED wall uses before it can be installed, and they mean different things by the question. Getting them mixed up is how a job ends up with a supply that trips on a white frame, or a cooling plant sized for a peak the wall reaches twice a year.
| Who asks | What they need | Not this |
|---|---|---|
| Electrician | Maximum power draw, and how it splits across circuits | Average power |
| HVAC consultant | Heat load in BTU/h or kW at the duty cycle it will run | Peak heat, which will oversize the plant |
| The client’s finance director | Kilowatt-hours a year, at the hours it will actually run | A watts figure of either kind |
The structural engineer wants a different figure again, and it has its own guide: LED wall weight.
Average power and maximum
Data sheets print two power figures per cabinet or per square metre, and they are far apart:
- Maximum power is every pixel at full white at full brightness. It is a real state — a white slide, a snow scene, a broadcast card — not a theoretical worst case.
- Average power is typical mixed content, conventionally about a third of maximum. It is what the wall costs to run.
Size the electrical supply on maximum. Estimate running cost and heat on average. Quoting the average to an electrician is the single most common way to get a wall commissioned and then tripped by the first all-white test pattern.
Both scale linearly with cabinet count, which makes them easy — total = per-cabinet figure × number of cabinets. The per-square-metre version is derived from that, and is the one to use when comparing two products with different cabinet sizes.
Watts per square metre, by product
How much power an LED wall uses per square metre depends on the product class more than on anything else: brightness is the main driver, so an outdoor wall at 5 000 nits draws several times what a fine-pitch indoor wall draws. These are the reference cabinets the free calculator ships with, each computed by the same engine.
| Product | Cabinet | Average W/m² | Maximum W/m² |
|---|---|---|---|
| Micro 0.78 COB | 600 × 338 mm | 178 | 543 |
| Micro 0.9 MIP | 600 × 338 mm | 188 | 568 |
| Fine pitch 1.25 COB | 600 × 338 mm | 198 | 593 |
| Fine pitch 1.5625 COB | 600 × 338 mm | 222 | 667 |
| Fine pitch 1.875 IMD | 600 × 338 mm | 257 | 765 |
| Indoor 2.5 SMD | 640 × 480 mm | 228 | 684 |
| Indoor 3.91 SMD | 500 × 500 mm | 320 | 960 |
| Rental 2.6 SMD | 500 × 500 mm | 380 | 1 140 |
| Rental 3.91 SMD | 500 × 500 mm | 360 | 1 040 |
| Outdoor 4.8 SMD | 960 × 960 mm | 271 | 781 |
| Outdoor 6.67 SMD | 960 × 960 mm | 304 | 868 |
| Outdoor 10 SMD | 960 × 960 mm | 326 | 977 |
These are typical figures for each class, not any one manufacturer’s. Before anybody sizes a supply, enter the real cabinet from the data sheet; the difference between typical and actual is often twenty per cent, and it is the maximum column that has to be right.
Circuits, phases and inrush
A wall is not one load. It is a set of cabinets chained into power runs, and the maker specifies how many cabinets may share a run — commonly four to eight indoors, fewer outdoors where each cabinet draws more.
Three things to settle before the offer goes out:
- How many circuits. Maximum wall power ÷ the usable capacity of one circuit, derated. Then round up, because the runs also have to divide sensibly across the wall.
- Single or three phase. Anything past about 7 kW is usually three phase, and the cabinets should be distributed so the phases stay balanced when the content is not.
- Inrush. Switch-mode supplies draw a large, brief surge at power-on. Enough cabinets on one breaker will trip it every morning, which is why staged or sequenced power-up exists.
None of this is your responsibility to design as a distributor, but all of it is your responsibility to hand over. An offer that states the maximum draw, the number of runs and the phase requirement is an offer the electrician can price from.
Running cost
The running cost is average power × hours × the tariff, and the only part of that you control is being honest about the hours. A reception wall runs twelve hours a day on weekdays; a roadside billboard runs eighteen, every day; a control room runs twenty-four. The same wall differs by a factor of three between those, before anybody argues about the content.
Put the kilowatt-hours on the offer, with the hours stated. A client who has been told what the wall costs to run is a client who does not come back with the question after the first electricity bill — and a competitor who quoted maximum power as if it were consumption has just told the same client the wall costs three times what it does.
Heat, and the HVAC conversation
Essentially all the electrical power an LED wall draws leaves it as heat. That makes heat load easy to calculate and easy to forget: 1 watt = 3.412 BTU per hour.
The question is which power figure to convert. Peak heat is the right input for a plant that must never be caught out; average heat at the real duty cycle is the right input for a plant that would otherwise be oversized by a factor of three. Give both, and say which is which.
This is not a small effect. A 30 m² indoor wall at 400 W/m² average is 12 kW — about 41 000 BTU per hour, about the same heat as a hundred people standing in the room, all day.
A worked example
A roadside outdoor screen: ten by five 960 mm cabinets at 6.67 mm, running eighteen hours a day, all year. Every figure here is computed by the same engine the calculator uses.
| Figure | Value | Who it is for |
|---|---|---|
| Wall size | 9.60 × 4.80 m · 46.08 m² | Everyone |
| Cabinets | 50 | Logistics and installation |
| Maximum power | 40.0 kW · 868 W/m² | Electrician — size the supply on this |
| Average power | 14.0 kW · 304 W/m² | Running cost and heat |
| Energy | 91 980 kWh per year at 18 h × 365 d | The customer’s finance director |
| Heat, peak | 136 486 BTU/h | HVAC, worst case |
| Heat, average | 47 770 BTU/h | HVAC, sizing case |
| Receiving cards | 50 | Control system quotation |
The gap between peak and average is the whole point of the table. Sizing the supply on 14.0 kW would be a fault. Sizing the cooling on 40.0 kW would be an expensive one. The same wall weighs 1 350 kg, and what the rigger does with that is the other half of the hand-over.
What goes on the technical sheet
A technical sheet that accompanies a quotation should let the electrician and the HVAC consultant start work without ringing you. For power, that means:
- Power average and maximum, per wall and per square metre.
- The number of power runs and the phase requirement.
- Heat load at both average and peak, in BTU/h or kW.
- Kilowatt-hours a year, with the hours per day stated.
- Receiving card count, processor model, and the redundancy scheme if there is one.
The free LED wall calculator computes every figure on that list except the processor, and easyLED PRO prints them as a sheet with your logo alongside the offer.