How much does deck lighting cost?
Deck lighting is cheap per fixture and easy to oversize. What you are buying is a safer stair and a deck you can use after dark.
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The numbers at a glance
- Post cap light
- $45 – $110 each
- Recessed step light
- $55 – $130 each
- Riser or hardscape light
- $50 – $125 each
- Transformer
- $180 – $380
- New GFCI circuit
- $150 – $400
What deck lighting costs, per fixture and per layout
Low-voltage deck lighting is priced by the fixture, with the transformer and the cable as separate lines. A typical deck takes eight to twelve fixtures, which puts most complete jobs between $700 and $1,600 installed.
The fixture price includes the light, the cable connection and the labour to mount it. Post caps replace the cap that is already on the post, so they add almost no labour. Step lights need a hole cut into the riser or the stringer, which is why they cost more to install than to buy.
The one item that surprises people is the power source. If there is no GFCI outlet within reach of the deck, adding one is $150 to $400 before the first light goes in.
Installed cost per fixture, 2026 national ranges
| Fixture | Installed cost | Where it goes |
|---|---|---|
| Post cap light | $45 – $110 | On top of each 4×4 or 6×6 post, replacing the cap |
| Recessed step light | $55 – $130 | Cut into the riser or the stringer of a stair |
| Riser or hardscape light | $50 – $125 | Under a bench, along a retaining wall, in a planter |
| String lights on posts | $35 – $90 | Strung between posts, one run per span |
Prices include the fixture, the cable connection and the labour. A transformer and a GFCI outlet are additional, and both are usually needed.
Which fixture goes where
Post caps are the default because they light the deck surface from above and they replace a part you already have. They are also the cheapest to install: no cutting, no drilling into a finished surface.
Step lights solve a different problem. A code-compliant stair is not the same as a visible stair, and the difference is the shadow line on each tread. Recessed lights in the riser, or a strip on the stringer, light the edge that a foot actually lands on.
Riser and hardscape lights are for the parts of the deck you do not see: the bench, the steps down to the lawn, the wall that retains the grade. String lights are decorative rather than functional, and they suit a covered pergola more than an open railing.
Matching the fixture to the job
| Goal | Fixture | Rule of thumb |
|---|---|---|
| See the deck surface | Post cap | One per post |
| See each step edge | Recessed step or riser | One per 2 – 3 steps |
| Light a bench or wall | Hardscape light | One per 4 – 6 ft |
| Atmosphere, not visibility | String lights | One run per span, 8 – 10 ft high |
The safest layout combines two of these: post caps for the deck, step lights for the stair. A deck lit only from above leaves the stairs in shadow.
Transformer sizing: the 80 percent rule
Low-voltage systems run on a transformer that converts household current to 12 volts. It has to be sized for the total wattage of every fixture on the run, with headroom: the usual guidance is to keep the load at about 80 percent of the transformer rating.
That headroom is not padding. Voltage drops along a long cable run, and a transformer running at its limit runs hot and shortens the life of every lamp on the circuit. Ten 5-watt fixtures need a 60-watt transformer; twenty need 120 watts.
If you plan to add lights later — and most people do — buy one size up now. A transformer is $180 to $380 and replacing it later costs as much as the upgrade itself.
- Add the wattage of every fixture, then divide by 0.8 to get the minimum transformer size.
- Ten 5 W fixtures: 50 W ÷ 0.8 = 62.5 W, so a 75 W transformer.
- Keep the cable run under about 100 ft, or use a heavier gauge to limit voltage drop.
- Mount the transformer where it is dry and within reach of a GFCI outlet.
- Buy one size up if you expect to add fixtures.
A worked example: six posts and four steps
A 12 × 16 ft deck with six posts, a four-step stair down to the lawn, and an outlet on the house wall within reach.
6 post caps and 4 recessed step lights
Priced at national averages, with the transformer and cable included and the outlet already in place.
- 6 post cap lights$70 each installed
- $420
- 4 recessed step lights$85 each, including the cut-out
- $340
- 60 W transformerSized at 50 W load, one size up for future lights
- $240
- Low-voltage cable, 90 ftClipped to the underside of the frame
- $110
- Labour and waterproof connectionsTwo people, half a day
- $260
$1,370 — about $137 per fixture, all in
If the deck has no nearby outlet, add $150 to $400 for a GFCI circuit. That is the item most quotes leave out.
The installation details that decide whether it lasts
Low-voltage cable is safe to handle, but it is not maintenance-free. The connections are the weak point: a twist-on connector that fills with water fails within a season, and the symptom is one dark fixture in the middle of a run.
Use gel-filled or heat-shrink connectors, mount them above the deck surface where water drains away, and leave a small drip loop at each fixture. Clip the cable to the frame rather than laying it on the ground, where string trimmers and animals find it.
The transformer needs its own protection too: plug it into a GFCI outlet, keep it off the ground, and leave access to the breaker on the unit. A transformer buried behind a lattice skirt is a transformer nobody can reset.
- Gel-filled or heat-shrink connectors, never plain twist-ons outdoors.
- Run the cable under the frame, clipped, not on the ground.
- Leave a drip loop at each connection.
- Mount the transformer above grade, with the breaker reachable.
- Test the whole run before the deck boards go back down.
How long deck lighting takes
A one-day job on an existing deck, half a day on a deck under construction.
Layout and fixture choice
1 – 2 hours
Post count, step count and fixture type fixed; transformer size calculated.
Rough-in
2 – 4 hours
Cable run clipped to the frame, transformer mounted and connected.
Fixture installation
2 – 4 hours
Post caps swapped, step lights cut in, connections made.
Test and adjust
30 minutes
Every fixture checked, transformer load measured, timers or photocell set.
One day in total on an existing deck, assuming power is already there. A new circuit adds a separate electrician visit.
The six most expensive deck lighting mistakes
Most failures are connections, not fixtures.
Sizing the transformer exactly to the load
A transformer at 100 percent runs hot and shortens lamp life. Keep the load at 80 percent or less.
Using indoor connectors outdoors
Plain twist-on connectors fill with water. Gel-filled or heat-shrink connectors are the difference between five years and one season.
Lighting only from above
Post caps light the deck, not the stairs. Steps need their own lights at the tread edge.
Laying cable on the ground
String trimmers, animals and water destroy it. Clip it to the underside of the frame.
Burying the transformer
It needs ventilation, protection from water and access to its breaker. Behind a lattice skirt it gets none of those.
Skipping the GFCI
Outdoor low-voltage equipment still needs ground-fault protection. The outlet is $150 to $400 and it is not optional.
Before you buy deck lights
Count first, then size the transformer, then choose fixtures.
- Count the posts and the steps you want to light.
- Decide whether the stair needs its own lights, not just the deck.
- Add the fixture wattage and size the transformer at 80 percent load.
- Confirm there is a GFCI outlet within reach, or budget for one.
- Ask for gel-filled or heat-shrink connectors in the quote.
- Confirm the transformer has a photocell or timer if you want automation.
- Check that the post caps fit the actual post size on your deck.
- Agree who tests the run before the deck boards are closed up.
Put a number on your project
Deck Lighting Calculator
Estimate low-voltage deck lighting.
Patio Calculator
Estimate patio base, materials and cost.
Fence Calculator
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Planning estimate only — confirm quantities with your supplier or contractor before ordering.
Frequently asked questions
How much does it cost to light a deck?
Low-voltage fixtures run $45 to $130 each installed. A typical 10-light layout with a transformer and cable lands between $700 and $1,600. Adding a GFCI outlet, if there is none, costs $150 to $400 more.
How many lights should a deck have?
One post cap per post, plus one step light per two or three steps. A 12 × 16 ft deck with six posts and a four-step stair typically takes ten fixtures in total.
What size transformer do I need for deck lights?
Add the wattage of every fixture and keep the total at about 80 percent of the transformer rating. Ten 5-watt lights need a 75-watt transformer; twenty need 150 watts.
Can I install low-voltage deck lighting myself?
Yes, if the deck has a GFCI outlet nearby. The cable clips to the frame and the fixtures connect with push or crimp connectors. The parts that fail are waterproofing the connections and sizing the transformer.
Do deck lights use a lot of electricity?
Very little. Ten 5-watt fixtures running five hours a night use about 0.25 kWh, which is a few cents a day at typical rates. The transformer losses are small at that load.
Are solar post caps a good alternative?
They avoid the wiring entirely and cost about the same per fixture, but output drops in winter and the batteries need replacing every year or two. For a deck with no power nearby, they are the pragmatic choice.
Where these numbers come from
Ranges are installed national averages for 2026 on an existing deck with power available. A new circuit and a pergola structure change the total.
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