Pond lighting is something to be very careful with. We are talking about putting electricity into water. If that doesn't grab your attention then nothing probably will.

I highly suggest that you have a licensed electrician run the power lines to your pond. Be sure that they install ground fault interrupter boxes. These will kill the power if moisture is ever detected in the circuit.

That is a good thing!

TRANSFORMERS

Next you need to step the 120 volt power down to 12 volts. This is done via the transformer. The wattage you get will depend on the transformer you choose. The higher the wattage, the more 12v lights and accessories you can run.

To determine the lighting load, one only has to think back on their 12th grade physics class. If you didn't take physics...don't worry. Here is the formula.

Volts x amps = watts

This means your voltage is always the same at 12 volts. If you total up your wattage needs, and the transformer is sold by amperage, you can figure out the amps needed,

If the fixture you wanted to add is rated in amps, you can figure out the watts and whether your transformer has the juice to run it. You can go either way with a bit of math.

USE REVERSE ENGINEERING

Before you go out and purchase your lighting is is better that you reverse enginneer the whole thing first.

If you know that you want 10 lights and that each lighting fixture is going to require 15 watts, then you are going to need a 150 watt transformer. If you buy a 100 watt transformer, you will be disappointed and your pond will be under-lit.

A good rule of thumb is to buy more transformer than you think you'll need. If you determine that you need 150 watts, buy a 200 watt transformer.

The 200 watt transformer may be more expensive, but it is cheaper than ending up purchasing two 150 watt transformers.

This will give you room to add more lights to you pond, later, and you will be able to run your regular garden lightening off of the same transformer. (Once your better half sees pond lighting, be prepared to install garden lighting.)

USE EXTRA WIRE

When you are laying out your pond lighting, be sure to leave an extra two to three feet of wire at each fixture. Yes, light bulbs will burn out and the extra length of wire will give you the ability to lift the lighting fixture up out of the water to change the bulb.

This is much easier than the alternatives.

Changing the bulb underwater and/or draining the your pond to change the pond is a royal pain in the anatomy.

Be absolutely sure that you unplug the transformer before changing any bulbs!

Bottom line...get the right transformer and you will have fewer headaches and be much happier with your garden pond lighting.