What Size Wire Is Used for Low Voltage? A Complete Guide for Safe and Efficient Wiring
If you’ve ever worked on low voltage wiring—whether for landscape lighting, CCTV systems, thermostats, or smart home devices—you’ve probably asked yourself: What size wire should I use for low voltage applications?
The wire size you choose matters more than you might think. It affects how efficiently power travels from your source to your device, how safe your system is, and how long your components last. In this guide, we’ll walk through how to choose the right wire gauge for your low voltage system and avoid common mistakes. Our experienced team of low voltage wiring contractors in San Jose ensures every installation follows safety codes and delivers efficient power distribution.
Understanding Low Voltage Wiring
Low voltage systems typically operate at 50 volts or less—most commonly 12V or 24V. These systems are used for applications like:
- Landscape and outdoor lighting
- Security cameras and alarm systems
- Doorbells and intercoms
- Thermostats and HVAC controls
- Home automation and data networks
Because the voltage is lower, the current (amperage) must travel efficiently through the wire without losing too much energy as heat or resistance. That’s why choosing the right wire size is essential for performance and safety.
What Wire Size Is Commonly Used for Low Voltage?
The most common wire sizes for low voltage applications range between 12 AWG and 22 AWG, depending on the distance and the power demand of your device.
Here’s a quick breakdown:
| Wire Gauge (AWG) | Typical Use | Recommended Max Distance (12V) |
|---|---|---|
| 12 AWG | High-power LED lighting, long runs | Up to 100 ft or more |
| 14 AWG | Medium-power lighting, CCTV, alarms | Up to 75 ft |
| 16 AWG | Shorter lighting runs, small loads | Up to 50 ft |
| 18 AWG | Doorbells, thermostats, intercoms | Up to 30 ft |
| 20–22 AWG | Low-current devices, sensors | 10–20 ft |
These values can vary depending on your total wattage and the acceptable voltage drop for your system.
How to Choose the Correct Wire Size
There are three main factors to consider when selecting wire size for low voltage systems:
- Voltage (V) – Most low voltage systems are 12V or 24V DC.
- Current (A) – How much current your device draws.
- Distance (ft) – The longer the wire, the more resistance it adds.
As a general rule:
The longer the wire run, the thicker the wire you need.
Using a wire that’s too small can lead to:
- Voltage drop (dim lights, weak camera feeds)
- Overheating
- Shortened equipment lifespan
To calculate the proper wire size, many electricians use voltage drop calculators or online charts that take into account amperage and distance. If you’re troubleshooting low power issues, it’s important to know how to tell if a battery has low voltage.
Common Applications and Recommended Wire Gauges
1. Low Voltage Lighting Systems
For landscape or outdoor lighting, wire gauge usually depends on how many fixtures you’re powering and the total run length.
- Use 12 AWG for long runs or heavy loads
- Use 14–16 AWG for moderate distances
- Always use direct-burial rated wire for outdoor installations
2. CCTV and Security Systems
Most CCTV camera systems operate at 12V DC and draw less than 1 amp per camera.
- Use 18 AWG for short runs under 100 ft
- Use 16 AWG for longer runs to prevent voltage drop
- For data, Cat5e or Cat6 cables are often paired with power wires in combo cables
3. Smart Home and Thermostat Wiring
For low-current control systems like thermostats or sensors:
- 18–22 AWG wire is typically sufficient
- Use stranded wire for flexibility in tight spaces
4. Audio and Intercom Systems
For speakers or multi-room audio systems:
- Use 16 AWG for short runs
- Use 14 AWG for longer distances or higher wattage speakers
Safety Tips for Low Voltage Wiring
Even though low voltage systems carry less risk of electric shock, safety still matters:
- Always turn off power before wiring.
- Use wire that’s UL-listed and rated for your voltage type.
- Avoid mixing low voltage and high voltage cables in the same conduit.
- Follow California Electrical Code or NEC (National Electrical Code) Article 725 for low voltage installations.
- Label all wires clearly for maintenance or troubleshooting later.
Tools and Materials You’ll Need
- Low voltage rated cable (12–22 AWG)
- Wire strippers and crimpers
- Connectors or terminals
- Multimeter for testing voltage and continuity
- Cable staples or conduit for secure routing
Having the right tools helps ensure a clean, reliable, and code-compliant installation.
When to Hire a Professional
If your system involves multiple devices, long cable runs, or commercial wiring, hiring a licensed low voltage contractor is the safest choice.
Professionals ensure:
- Proper cable sizing and routing
- Compliance with California electrical codes
- Neat and organized installations
- Testing and certification for performance
Final Thoughts
So, what size wire is used for low voltage? It depends on your setup, but most projects fall between 12 and 18 AWG. The key is to balance your wire gauge with the voltage, current, and distance of your system. Low voltage wiring is essential for many devices. Learn more about what types of equipment use low voltage in both homes and businesses.
Choosing the right wire size keeps your low voltage network safe, efficient, and long-lasting — whether you’re wiring security cameras, smart devices, or outdoor lighting.
If you’re unsure which size to use, reach out to a certified low voltage technician for professional advice and installation.