Determine the size transformer you need by counting the total number of lamps in your lighting plan and multiplying that number by the wattage of each lamp. Buy a transformer that's rated to carry 20 to 25 percent more than your total wattage. For example, if you have twelve 20-watt lamps in your plan, your total wattage is 240. Add a 20 to 25 percent excess to increase the wattage by 48 to 60 watts. You would need a 300-watt transformer.
Buy a transformer based on its continuous wattage. For example, a transformer that runs 300 watts continuously may be rated as high as 400 watts, but you'll be happier with its output if you purchase it for a system that requires slightly less than 300 watts.
Buy a transformer that has multiple taps: 12, 13, and 14 volts. That allows you to tap onto the 13- or 14-volt lines if you have a long run; the higher capacity improves the flow of electricity through the cable and ensures bright lights at the end of a long run. Tap onto the 12-volt line for close-in lighting. Splitting up the electrical lines among taps ensures that the lamps get more even voltage and the front lamp doesn't burn up. Although you may tap into more than one line, it's important that the total wattage on all cables does not exceed the transformer's rated wattage.
- Cable. Electrical cable brings electricity from the transformer to the light fixtures. Low-voltage cable is usually two-conductor (two wires encased in insulation and fused together) direct-burial (DB) cable with wire sizes numbered 12, 14, and 16. Try not to exceed a length of 160 feet.
- Wire nuts. These solderless connectors screw on over stripped wires to ensure good electrical connections. Wire nuts are color-coded to the size of the wire.
- Electrician's tape. This black plastic tape is waterproof and protects from moisture.
- Light fixtures and lamps (lightbulbs). Various manufacturers produce fixtures for low-voltage lighting systems. The fixtures come wired and simply connect to the low-voltage cable.
Tier lighting costs $9 to $20 per unit. Solar versions range from $13 to $30. Entrance lights will make a statement from $10 to $20 per unit. Floodlamps that illuminate a large area will cost between $33 to $63 dollars. It's also not a bad idea to install small floodlights triggered by a motion detector. These vary in price from $11 to $25. This same per-unit price range applies to well and mushroom lights.
- Light directed up is more interesting than light pointed down. Floodlights at ground level illuminate the deck. A well light shines up at the tree; these low-profile lights can be set into the soil so as not to interfere with the lawnmower.
- Night lighting should never attempt to duplicate daylight. Low-level glows create interest and shadows.
- A glow of light rather than the fixture itself should be apparent. Low-profile fixtures easily hide behind plants.
- Light adds dimension to the landscape. Darkness makes everything appear two-dimensional. Lighting helps the eye to pick up depth, especially if lights are used in corners rather than on flat expanses of wall.
- If you need security lighting, install floodlights that operate separately from landscape lighting.