Updated September 2026. This post was rewritten around pixels, which have replaced dumb RGB for nearly every holiday project.
We often get asked how many lights can be connected to a controller, what power supply to use and what wire to run. This post answers those questions for pixel lights and pixel controllers.
A word of caution first: if you get the power side wrong, the results range from flickering lights to damaged hardware and, in the worst case, a fire. Don't "wing it." If you'd rather just have the answer, fill out our project design form and we'll put together a recommendation and a complete quote, or start with one of our Ready2Run packages, where the power math is already done.
The key is to see the lights and the controller as parts of one system:
Pixels → Pixel wiring → Controller → Power wiring → Power supply
Let's work through the chain.
1. The pixels
Everything starts with the lights, because every other part is sized to them. When choosing pixels, consider:
- Format. Nodes, strip, modules or bulbs, depending on how you'll mount them and whether they need to follow corners or curves. For house outlines, MegaTrees and props, 12mm nodes are the most common choice.
- Voltage. Pixels are usually 5v or 12v DC. 12v runs farther before you need to inject power and is the more forgiving choice for most holiday projects. 5v is slightly more efficient but needs more careful power planning.
- Power draw. This is the number that drives everything else. Our 12v 12mm nodes draw about 45 milliamps each at full white, or about 0.55 watts per pixel.
Always figure power at full white (red, green and blue all on), since that's the most a pixel can draw.
2. The pixel wiring
This is the wire between each pixel in a string, or the circuit board in a strip. It carries power from the controller down the run, and it's where most power problems start.
There's no standard here. One vendor's nodes may use thick 18 AWG wire while another's look identical but use thin 22 AWG. Thinner wire loses more power over distance, so the pixels at the end of the run get less voltage than the ones at the start.
Ideally, your vendor tells you how many pixels can run before you need to inject power. Our 100-count 12mm node strings, for example, are designed to run the full 100 nodes with power fed at the start. If your vendor doesn't publish this, measure it yourself: set the run to full white for 15 to 30 minutes, then measure the voltage at the first and last pixel with a meter. A drop of 10 to 20% is usually fine. Much more than that and you'll see dimming, color shift or random flicker at the end of the run.
When a run is longer than the pixels can carry power, you inject power: run heavier wire from the power supply to a point partway down the run and connect it to the string's power and ground there. The data passes straight through.
3. The controller
A pixel controller receives data from your sequencing software over your network (E1.31) and sends it to each pixel. It also passes power from the power supply through to each output. When sizing a controller, check:
- Pixels per output. How many pixels each output can drive. This is usually the limit you hit first on long runs.
- Current per output. How many amps each output can supply. Divide your run's watts by the voltage to get amps: a 100-pixel run at 0.55 watts each is 55 watts, or about 4.6 amps at 12v.
- Current per bank and per controller. Larger controllers split their outputs into power banks, often each fed by its own power supply.
Don't size by the fuse. The fuse is there to protect against a short, not to tell you how much the output can carry.
Our Controller Selection Wizard will match a controller to your pixel count and power, or see our Ready2Run pixel controllers.
4. The power wiring
This wire carries power from the power supply to the controller, and to any power injection points. Size it by two things: the total power of every pixel it feeds, and the distance it has to run. Two controller outputs of 55 watts each need a wire that can carry 110 watts over that distance. Our technical guide to wire selection has the charts.
5. The power supply
The power supply is the last thing you choose, and it's simple once the rest is done:
- Total power. Add up every pixel it feeds at full white, then add 10 to 20% headroom. 576 pixels at 0.55 watts is about 317 watts, so you'd want a supply rated comfortably above that.
- Voltage. Match your pixels: 12v pixels need a 12v supply.
- Enclosure and cooling. Outdoor supplies need to be protected from water but still get enough airflow, since larger supplies often have fans. Our Ready2Run controllers come with the power supply already mounted in the enclosure with the controller.
See our power supplies.
Putting it together
Work from the pixels up: count your pixels, figure watts at full white, split long runs or plan power injection, pick a controller with enough outputs and capacity, size the wire and pick a supply with headroom. For a complete worked example on a real house, see our detailed house outline design guide.
Related posts:
- See the effects of power draw on long runs of pixels
- Where do I start when designing a new pixel project?
- Dumb RGB or pixels: which is right for me?
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