How to Install Landscape Lighting Transformers?

Low-voltage landscape lighting turns a GTA backyard from a dark rectangle into a usable evening space — path lights, spotlights on trees, uplights on stone walls, deck accents. The transformer is the heart of the system, converting 120 V household power into safe 12 V or 15 V for the fixtures. Get the transformer install right and the system works for 15 years without attention. Get it wrong and fixtures dim, transformers hum, and homeowners chase problems all summer. This guide walks Ontario homeowners through how to install landscape lighting transformers, what size to buy, and what the Ontario Electrical Safety Code requires.

Short answer: mount outdoors near a GFCI receptacle, size to 80% of connected load, run 12/2 low-voltage cable to fixtures

Direct answer: mount the transformer on an exterior wall within reach of a weatherproof GFCI-protected receptacle (typically at 1.5 m above grade), size it so the total connected fixture wattage is under 80% of the transformer rating, run 12/2 direct-burial low-voltage cable from transformer to fixtures, and use waterproof connectors at every fixture tap.

Sizing the transformer

• Add up all fixture wattages. Ten 5 W LED path lights = 50 W. Five 12 W spotlights = 60 W. Total = 110 W.
• Divide by 0.8 for the 80% rule. 110 / 0.8 = 138 W minimum transformer rating.
• Round up to next available size. Common sizes: 60 W, 100 W, 150 W, 200 W, 300 W, 600 W. Pick 150 W or 200 W for this example.
• Add 15-20% for future expansion. Landscape lighting always grows; buy one size up if the price difference is modest.

Mounting location

• Exterior wall facing the yard, protected from direct rain hit.
• 1.5 m above grade to stay out of snow and mower reach.
• Within reach of a GFCI receptacle. Section 26 of the Ontario Electrical Safety Code requires GFCI protection on outdoor 120 V receptacles.
• Not inside the garage unless the transformer is rated for indoor use — outdoor transformers are usually IP44 or better.

Step-by-step: the install

1. Choose the location and mark the mounting screws. Verify a GFCI receptacle is within reach of the transformer’s plug.
2. Turn off the receptacle breaker. Verify with a non-contact voltage tester.
3. Mount the transformer to the wall using the provided screws or wall anchors.
4. Plug the transformer into the GFCI receptacle. Some transformers hardwire to a junction box; low-voltage transformers usually use a standard plug.
5. Run the low-voltage cable from the transformer output to the first fixture. 12/2 direct-burial cable is standard; run in shallow trenches (150-300 mm deep) or under mulch depending on manufacturer specs.
6. Connect fixtures with waterproof connectors. Silicone-filled push-in connectors (King Innovation King Wire, DryConn) prevent corrosion at every splice.
7. Balance the load. Larger transformers have multiple 12 V outputs (COM, 12V, 13V, 14V) for compensating voltage drop on longer runs. Put close fixtures on the 12 V tap; distant fixtures on the 13 V or 14 V tap.
8. Program the timer or photocell. Most transformers include astronomic timers that automatically adjust for sunset. Alternatively, install a photocell that triggers at dusk.
9. Test at night. Confirm every fixture lights, brightness is even, and the timer/photocell triggers on schedule.

Voltage drop math (avoids the far-end dim problem)

Direct answer: 12 V circuits drop voltage significantly over long runs. A 12/2 cable at 5 A loses about 0.6 V per 15 m of run — that is 5% of the 12 V. Fixtures at the far end run dimmer than fixtures near the transformer.

Fixes: (1) use a hub-and-spoke wiring pattern where each run is short, (2) split the load across multiple transformer taps of different voltages (COM to 12 V for near, COM to 14 V for far), or (3) use a T-tap pattern instead of daisy chain. The result: consistent brightness across the yard.

What can go wrong

• Transformer humming. Usually a loose lamination inside the transformer. Sometimes fixable by tightening the mounting screws; often replace.
• Far fixtures dim. Voltage drop. Use higher-voltage tap or shorter runs.
• All fixtures off. Transformer failed (usually the internal fuse or timer), receptacle GFCI tripped, or the cable was cut somewhere.
• Timer not triggering. Photocell dirty or covered; astronomic clock lost time settings.
• Corrosion at connectors. Waterproof connectors were skipped. Replace with silicone-filled ones.

Expert tip from our ESA-licensed electricians

In our experience installing landscape lighting across GTA back yards — particularly in Etobicoke, North York, and Vaughan estates — the single detail that saves customers years of maintenance is spending $2 per fixture on silicone-filled waterproof connectors instead of the twist-on wire nuts that come in cheap kits. Wire nuts corrode within one wet season and turn the whole system into a maintenance headache. Waterproof connectors last 15+ years without touching them. Same story for the transformer choice — spending $100 on a stainless-steel Kichler or FX Luminaire transformer with a real astronomic timer, instead of a $40 plastic big-box unit, means the system works reliably every night without homeowner intervention. Landscape lighting is one area where the cheap-parts penalty is high, and the good-parts payoff is invisible until you notice you never had to fix anything.

Related reading from ezsmart.ca

• Why do outdoor lights keep burning out?
• Are outdoor outlets required to be GFCI?
• GFCI tripping when it rains?
• Basic electrical tools
• Outdoor Lighting York Mills

Frequently Asked Questions

What voltage is landscape lighting?

Most residential landscape lighting is 12V, stepped down from 120V by a transformer.

Where should the transformer be mounted?

On an exterior wall near a GFCI-protected 120V outlet, above ground and in a weatherproof location.

What size transformer do I need?

Match total wattage of connected lights plus 20% headroom. Typical residential range is 300–600W.

Can I install the transformer myself?

Homeowner-friendly on your own property. The upstream 120V circuit is licensed contractor work.

Do I need a permit for landscape lighting?

Not for low-voltage 12V. Any new 120V outlet for the transformer needs a notification.

Contact us

Planning landscape lighting for your GTA yard and want an ESA-certified electrician to install a proper transformer and cable run? Call us at 416-838-9006 or visit our contact page — we will get back to you the same day.

Amir Azimipour

Electrician Since 2008 Journeyman Electrician Designated Master Electrician at EZSMART Corp