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Low Voltage Wiring Guide

You will need a low voltage wiring guide when planning your outdoor lighting.  This will help you decide what size wire, how many lights can be on each run of wire, and how to run your wire.

In this post, we will look at how voltage drop works, how it effects the amount of light each fixture will give out.  The brightness of the fixture will have an effect on the lighting that you use for landscape.

Now let us look at the details of my wiring guide.  For other items like the transformer, connectors, and planning your layout, see my posts here.

Voltage drop explained

Voltage drop happens when your wire is too small to handle the number of lights or is too long.  Having too long of a run will have the lights at the start of the run at 12 volts and the lights at the end having only around 8 volts. Low Voltage Wiring Guide-low voltage lightsThe lights will still work, but will not last as long if they are not running close to 12 volts.

Having too many lights on the same run will have the same effect.  The lights at the start of the run will have more voltage than the lights at the end of the run. 

To correct this problem, mapping your runs with a connection in the middle of the run going both ways will correct this problem.

How many watts of lights will be in the run

After you have mapped out where the lights will be you must include the wattage of each fixture.  This will help in deciding how to run the wire from the transformer.  must have the number fo feet between each fixture and the wattage of the lights at each location.  Try to limit each run to 100 to 150 watts of total output.

Divide the fixtures into areas for the best coverage and having the same number of watts in each run.  Long runs can be split in the middle and the number of lights will be cut in half.  This will ensure that all lights get close to the same power.

How to use the chart to find out the size of the wire that you will need

After you have made all of your plans on where the lights will go and how the wire is laid out, use the chart to get the correct size wire for your lights to prevent a lot of voltage drop.


Low Voltage Wiring Guide-Low Voltage wire guide chart

Wire chart from


Getting the correct low voltage wire for your lights will give you the best performance for each light.  If you follow these simple instructions, you should have no problem with having the same illumination at the start of your run to the end of your wire run.

Don't forget to get the correct transformer and wire connectors for your lights' best performance also.  For more information on transformers, see my post here.

If you have any questions or comments, let me know with the forms below and I will get back to you shortly.