How Do You Size Power Cables and Circuit Breakers for a 20 kW, 50 kW or 100 kW Outdoor LED Screen?
Answer first: Outdoor LED screen cable sizing starts with the display’s confirmed maximum power consumption, supply voltage, phase configuration and power factor. Convert maximum power into line current first. Then select the conductor and protective device according to corrected cable ampacity, installation conditions, voltage drop, fault protection and the electrical code governing the project.
For a worked example at 400 V three-phase with a power factor of 0.95, 20 kW, 50 kW and 100 kW LED screens draw approximately 30.4 A, 76.0 A and 151.9 A per phase. Using an illustrative 125% continuous-load sizing factor produces example nominal protective-device ratings of 40 A, 100 A and 200 A.
| Maximum LED screen power | 400 V 3-phase current | Worked breaker example* |
|---|---|---|
| 20 kW | 30.4 A | 40 A |
| 50 kW | 76.0 A | 100 A |
| 100 kW | 151.9 A | 200 A |
*Worked calculation only. Assumptions: 400 V three-phase, cos φ = 0.95 and an illustrative 125% continuous-load design factor. The final breaker and cable must follow the electrical standard adopted for the installation, together with actual ambient temperature, cable grouping, installation method, fault level and voltage-drop requirements.
Important standards note: The 125% factor used in this article is presented as a NEC-style continuous-load worked example, not as a universal international breaker-sizing rule. Projects governed by IEC-based, BS 7671, AS/NZS or other national requirements must use the rules applicable in that jurisdiction.
Assumptions used in this worked example. Uniview LED product documentation provides screen-side product data such as maximum and average consumption. It does not replace the electrical design calculations required for the site’s distribution system.
Unless stated otherwise, the examples below use: cos φ = 0.95, copper resistivity ρ ≈ 0.0225 Ω·mm²/m, an illustrative feeder voltage-drop target of approximately 3%, and — where specifically identified — a 125% continuous-load design factor.
Start with four inputs, not with a cable table
Many outdoor LED electrical-sizing errors begin before the installer opens a cable table. Confirm these four items first:
Step 1 — Turn LED screen area into design power
Uniview LED documentation may state LED display power consumption either per square meter or per cabinet. The two values cannot be compared until they have been converted to the same basis.
- Power per area: often expressed as maximum / average consumption in W/m².
- Power per cabinet: often expressed as maximum / average consumption in W/pcs.
For example, a 500 × 500 mm LED cabinet has an area of 0.25 m². If a configuration is specified at 700 W maximum per cabinet, its arithmetic equivalent is:
700 W ÷ 0.25 m² = 2,800 W/m²That conversion does not mean the figure should be substituted for a different product family’s W/m² specification. Pixel pitch, LED package, brightness, cabinet architecture, PSU design and driving method can all change the maximum power density.
Before cable or switchgear is ordered, confirm the maximum consumption of the exact model, pixel pitch and cabinet configuration in the bill of materials.
Area example. Using 750 W/m² maximum consumption as an illustrative outdoor LED value:
- 20 kW corresponds to approximately 27 m²
- 50 kW corresponds to approximately 67 m²
- 100 kW corresponds to approximately 133 m²
For a detailed area-based calculation, see How Much Power Does a 50 m² or 100 m² LED Wall Consume?
Step 2 — Convert LED display power into line current
Two basic formulas cover most preliminary LED display power calculations:
Three-phase: I = P ÷ (√3 × U × cos φ) Single-phase: I = P ÷ (U × cos φ)Where:
- I = line current in amperes
- P = maximum design power in watts
- U = line-to-line voltage for three-phase systems or supply voltage for single-phase systems
- cos φ = power factor
Worked example: 50 kW outdoor LED screen
For a 50 kW LED display supplied at 400 V three-phase with cos φ = 0.95:
I = 50,000 ÷ (1.732 × 400 × 0.95) = 76.0 A per phaseDo not assume the power factor. A value of 0.95 is used here only as a worked engineering assumption. The actual PSU specification should be confirmed for the selected display configuration.
If the true power factor is lower, the calculated current increases and may affect cable and protective-device selection.
| Maximum power | 400 V 3-phase | 208 V 3-phase | 230 V single-phase | 400 V worked breaker example* | 208 V worked breaker example* |
|---|---|---|---|---|---|
| 20 kW | 30.4 A | 58.4 A | 91.5 A | 40 A | 80 A |
| 50 kW | 76.0 A | 146.1 A | 228.8 A | 100 A | 200 A |
| 100 kW | 151.9 A | 292.2 A | 457.7 A | 200 A | 400 A |
*Example nominal ratings produced by applying a 125% continuous-load design factor and rounding upward. They are not universal construction specifications.
Maximum power and average power serve different purposes. Maximum consumption is normally the more appropriate starting point for electrical capacity planning. Average consumption is more useful when estimating energy use, operating cost and thermal load under typical content.
Step 3 — Select the circuit breaker or protective device
For projects governed by the U.S. National Electrical Code, continuous-load rules can require feeder and overcurrent-device sizing to account for 125% of the continuous portion of the load, subject to the applicable NEC provisions and permitted exceptions.
For IEC-based and other national systems, conductor and protective-device selection must be made using the requirements adopted for that project.
Do not use this shortcut: “LED screen current × 1.25 = universal breaker size.”
The correct interpretation is: calculate the load first, identify the governing electrical standard, and then apply the protection and conductor-sizing rules required by that standard.
Using the 125% worked-example assumption:
- 20 kW: 30.4 A × 1.25 = 38 A → illustrative nominal selection: 40 A
- 50 kW: 76.0 A × 1.25 = 95 A → illustrative nominal selection: 100 A
- 100 kW: 151.9 A × 1.25 = 189.9 A → illustrative nominal selection: 200 A
Five checks before the breaker is finalized
- Cable protection: the protective device and conductor ampacity must be coordinated as one design decision.
- PSU inrush current: large LED walls may energize many switch-mode power supplies simultaneously. Use manufacturer inrush-current data and the appropriate protective-device characteristics rather than simply installing a larger breaker to stop nuisance tripping.
- Fault-current rating: the protective device must have an interrupting capacity appropriate for the prospective fault current at the installation point.
- Ground-fault and shock protection: provide the protective measures required by the applicable code and project conditions.
- Local isolation: provide suitable means of safely disconnecting the LED display supply where required for operation and maintenance.
Step 4 — Size the cable: ampacity first, voltage drop second
A feeder can pass an ampacity calculation and still be unsuitable because of voltage drop. Conversely, a conductor with acceptable voltage drop can still be too small thermally. Both conditions must be checked.
4a. Corrected ampacity must cover the design current
Start with the current-carrying-capacity tables required by the applicable electrical standard and cable construction. Then apply correction or derating factors for the real installation.
- Ambient temperature — outdoor trays, rooftops and façade cavities can operate well above standard reference temperatures.
- Circuit grouping — several heavily loaded LED feeders in one tray or conduit can reduce allowable current.
- Installation method — free air, conduit, cable tray, buried cable and enclosed routes have different thermal conditions.
- Thermal insulation — cables passing through insulated structures may require additional derating.
- Harmonic loading — non-linear electronic loads can affect conductor and neutral design.
4b. Check voltage drop over the complete feeder route
ΔV = (√3 × I × L × ρ) ÷ A
%ΔV = (ΔV ÷ U) × 100
Where:
- L = one-way route length in meters
- ρ = conductor resistivity in Ω·mm²/m
- A = conductor cross-sectional area in mm²
For preliminary copper calculations, ρ ≈ 0.0225 Ω·mm²/m can be used as an illustrative operating-temperature value. Detailed electrical design should use the conductor resistance, reactance, temperature and calculation method required by the applicable standard and cable manufacturer.
Example A — 100 kW screen on a 60 m feeder
100 kW, 400 V three-phase, I = 151.9 A, one-way route = 60 m, conductor = 95 mm²:
ΔV = (1.732 × 151.9 × 60 × 0.0225) ÷ 95≈ 3.74 V
≈ 0.94% of 400 V
Example B — 50 kW screen on a 200 m feeder
50 kW, 400 V three-phase, I = 76.0 A, one-way route = 200 m, conductor = 35 mm²:
ΔV ≈ 16.9 V≈ 4.2% of 400 V
Increasing the illustrative conductor to 70 mm² reduces the simplified calculated voltage drop to approximately 8.46 V, or about 2.1%.
This is why route length can become the deciding factor in outdoor LED screen cable sizing.
Early-budget cable reference
| Maximum LED power | 400 V 3-phase current | Worked breaker example* | Indicative copper feeder range** |
|---|---|---|---|
| 20 kW | 30.4 A | 40 A | 6–10 mm², five-wire |
| 50 kW | 76.0 A | 100 A | 25–35 mm², five-wire |
| 100 kW | 151.9 A | 200 A | 70–95 mm², five-wire, or engineered multiple feeders |
*Worked 125% design example only.
**These conductor ranges are orientation aids for preliminary budgeting and RFQ comparison only. They are not construction specifications. Actual conductor size depends on cable type, installation method, temperature, grouping, harmonics, fault protection, termination rating, local code and voltage drop.
Step 5 — Design the downstream LED power distribution
Correct main-feeder sizing does not guarantee a reliable LED display. The screen-side distribution architecture also matters.
For the broader installation sequence, including structure, power, data and commissioning, see: LED Wall Installation Checklist: Structure, Power, Data and Commissioning .
Outdoor LED electrical design at a glance
| Maximum power | Approx. area at 750 W/m² | 400 V 3-phase current | 208 V 3-phase current | 400 V worked breaker example* |
|---|---|---|---|---|
| 20 kW | ≈27 m² | 30.4 A | 58.4 A | 40 A |
| 50 kW | ≈67 m² | 76.0 A | 146.1 A | 100 A |
| 100 kW | ≈133 m² | 151.9 A | 292.2 A | 200 A |
*Illustrative 125% continuous-load calculation only.
The screen-area figures above use 750 W/m² maximum consumption only as an example to illustrate the relationship between LED wall area and electrical load. Actual maximum power must always come from the exact display configuration being supplied.
Nine mistakes that can increase LED screen electrical cost
- Sizing the feeder from average consumption instead of confirmed maximum design power.
- Confusing W/m² with watts per cabinet.
- Ignoring power factor and treating kW as though it directly equals electrical apparent power.
- Using cable-table ampacity without applying installation correction factors.
- Checking conductor ampacity but ignoring voltage drop on long feeder routes.
- Increasing breaker size to stop nuisance tripping without investigating PSU inrush and protective-device characteristics.
- Automatically downsizing the neutral without assessing non-linear-load harmonics.
- Leaving surge protection, earthing, fault protection or isolation until after the screen structure has been installed.
- Ordering feeder cable before the final LED model, pixel pitch, cabinet quantity and maximum power have been confirmed.
What should go into the electrical tender?
- Maximum consumption of the exact LED display configuration
- Whether power is specified per m² or per cabinet
- Average consumption for operating-energy estimates
- Supply voltage, phases and frequency
- Confirmed PSU power factor
- Available inrush-current and harmonic information
- Feeder route length
- Cable installation method
- Expected maximum ambient temperature
- Circuit grouping conditions
- Main feeder and local distribution architecture
- Earthing and bonding arrangement
- Surge-protection strategy
- Local isolation requirements
- Electrical standard adopted for the project
Why model-specific LED power data matters
Outdoor LED products with similar cabinet dimensions can have substantially different maximum and average power consumption because of differences in pixel pitch, LED package, brightness, driving architecture and power-supply configuration.
Uniview LED configuration documentation can provide model-specific information such as maximum and average power consumption, cabinet dimensions, input-voltage range, weight and environmental protection data.
For feeder planning, request the configuration sheet for the exact model and pixel pitch in the project, rather than relying on data from a similar-looking LED display.
Product example: UR Pro Series Outdoor LED Display
Request Confirmed Power Data for Your LED ProjectTechnical standards and reference framework
The calculations in this article should be read together with the product documentation and electrical regulations that govern the actual installation.
- Uniview LED product configuration sheets — model-specific maximum and average power consumption, cabinet configuration and electrical input data.
- Uniview LED installation and user documentation — product-side installation, connection, environmental and safety requirements.
- NFPA 70 / National Electrical Code — for projects where the NEC is the governing code, including applicable continuous-load, conductor and overcurrent-protection provisions.
- IEC 60364-1:2025 — fundamental principles and safety requirements for low-voltage electrical installations.
- IEC 60364-5-53 — selection and erection of electrical equipment used for protection, isolation, switching, control and monitoring.
- Applicable national wiring regulations — such as locally adopted NEC provisions, IEC-derived standards, BS 7671, AS/NZS requirements or other jurisdiction-specific regulations.
- Cable and protective-device manufacturer data — for ampacity, termination limits, temperature correction, trip characteristics, fault ratings and coordination.
Always confirm the edition of the electrical standard legally adopted for the project location before final design and construction.
Three questions to answer before ordering cable
-
What is the confirmed maximum power?
Is the figure for the exact screen configuration, and is it expressed in W/m² or watts per cabinet? -
What supply will the screen actually use?
Confirm voltage, number of phases, frequency and the power factor used in the calculation. -
What are the real cable-route conditions?
Confirm feeder length, installation method, ambient temperature, circuit grouping and the electrical standard governing the project.
Engineering disclaimer: This article is intended for LED display system planning, specification comparison, RFQ preparation and preliminary electrical budgeting. It is not a substitute for a project-specific electrical design.
Final cable size, protection, earthing, surge protection, isolation, fault-current coordination and distribution architecture should be confirmed by the qualified electrical professional responsible for the installation.