What Size Transformer Do I Need For Landscape Lighting? Full Guide

Can you just get the cheapest transformer available?

When operating low voltage landscape lights, you need a transformer to transform your standard house line voltage 110V or 120V into low voltage 12V or 24V, the current needed to operate low-voltage landscaping lights. This enables your lights to function accurately. Low-voltage transformers are usually installed outside and plugged into your household current through an outside electrical outlet.

Warning! If you connect you low voltage lights straight to line power 120V, the higher voltage would cause them to burn out instantly.

Transformer sizes

Transformers commonly range from 120- to 900-watt capacity.

Pairing the size of the transformer to the lighting design is important for good operation and function of your light system.
Many transformers come with connections for lights of various wattage for versatility, so you can use the same transformer for different light systems.

Some transformers even include features like, motion detectors for turning lights on and off, photocells to turn lights on at precise light levels and programmable timers.

Transformers For Landscape Lighting – Top List

BrandTypeCheck PriceRating 1-5
120W with Sensor and Weather Shield for Low Voltage Landscape Lighting $4.4
Paradise by Sterno Home
12V 200W Low Voltage Landscape Lighting Transformer with Dusk-to-Dawn Timer $4,3
300 Watt (12V-13V-14V-15V) Multi-Tap Low Voltage Transformer for Landscape Lighting $4.7
600W Clamp Connect Transformer with Timer/Photocell $4.6

How to calculate the transformer size?

  • So, to solve the question about how many landscape lights you can connect to which transformer wattage, we need first look at some of the basic lighting design specifications and plans.
  • How many lights will you be installing?
  • What is the entire watts and voltage amp draw of the landscape lights being installed in an area?

Add up the wattage of each light in your landscape lighting design:

For example, if you intend to use 20 pieces of 12-watt lights, multiply 12 times 20 for the total wattage needed. In this example, the total wattage is 240. Then you must multiply the total wattage by 1.25 to adjust for loss due to cable distance. For the example, 240 x 1.25 = 300. The final number 300W determines how large the transformer is that you`re going to need for your system.

Pick a transformer that supplies no less than the required wattage and no more than 35 percent more. Picking a transformer with slightly higher wattage will let you add a few more lights in the future.
This consideration enables your landscape lights to work properly for many years ahead and will decrease issues with lights failing or ending up with weak outputs further down the line of wire connections throughout the property landscapes.

Wire plays a major role in your lighting design plans

Additionally, when considering what wire gauge to use for your landscape lighting design installation, it is best to realize that different gauges have their individual pros and cons.
Smaller wire sizes are usually more economical and larger wire sizes are stronger, though the smaller ones will also reduce the distance of power being provided to your lights in the ground, and may need a conduit to stay safe from dreaded landscaper cuts to your lighting connections.

  • Examples of installing your landscape lights with specific wire gauges:
  • A 300-watt transformer can power about 100 feet of 16 gauge
  • or 150 feet using 14 gauge
  • or 200 feet when using the most common 12 gauge cables.

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