Before you begin. This procedure is general reference information, not professional advice. Equipment varies by manufacturer, model, and year. Always follow the documentation supplied with your equipment — where it differs from this page, follow the manufacturer. Verify that you have the tools, the working conditions, and the ability to do this task safely. If anything is unclear, if the equipment is damaged, or if the task exceeds your experience, stop and use a qualified professional. You are responsible for your own safety and for the outcome. This site accepts no liability for any loss, damage, or injury arising from the use of this information.
Specifications marked unverified could not be traced to a manufacturer source. Do not rely on them — obtain the value from your equipment documentation.
Summary
Garden lighting fails in a boring, predictable way: a lamp dies, someone puts in whatever was on the shelf, and three years later the transformer is running warmer than it should on a load nobody has ever added up. This page does the two jobs together. You unplug the transformer, change the lamps, and then total what the system now draws and compare that total with the rating printed on the transformer itself. The whole procedure lives on the 12 volt secondary side, and the only thing you do to the household supply is pull a plug out of an outdoor socket.
On the number that matters, the honest answer is that it lives on your equipment and not on this page. Kichler publishes the rule plainly: the total VA of the system should not exceed the wattage value of the transformer. Hinkley asks for the same total plus some spare capacity for fixtures added later. Neither of them publishes a percentage, and neither of them publishes a derating of the transformer's rating for a long cable run — so this page publishes neither, and it says so rather than borrowing a figure from somewhere that never measured it. What you will get here is the method, the two published values we could actually trace, and a clear line at the point where the job becomes an electrician's.
Safety
DISCONNECT THE PLUG OF THE TRANSFORMER FROM THE RECEPTACLE BEFORE YOU OPEN A FIXTURE.
Do not open the case of the transformer at any time. The conductors inside that case can kill you.
Necessary equipment
| Item | Note |
|---|---|
| Multimeter that measures alternating voltage optional | Kichler says to measure the voltage at the last fixture. |
| Clean cloth or clean gloves | Hold a new halogen lamp with the cloth. |
| Pen and paper | Write the value of each fixture on paper. |
| Flashlight optional | The marks on a lamp base are small. |
| Documentation for the transformer and the fixtures | This documentation gives the rating of the transformer and the lamp type of each fixture. |
| New lamps material | The correct lamp type and the maximum wattage are on the fixture. |
Remove the power from the system
Estimated 11 min
- Set the switch or the timer of the transformer to OFF.<1mReport a problem with step 1, Remove the power from the system
- Disconnect the plug of the transformer from the receptacle.<1mReport a problem with step 2, Remove the power from the system
- Hold the body of the plug.
- Do not pull the cord.
- Wait 10 minutes.10mReport a problem with step 3, Remove the power from the system
- A halogen lamp stays at a high temperature for several minutes.
- An LED lamp becomes cool more quickly.
Change the lamps
Estimated 11 min to 22 min
No tier-1 source was found for this value. Take it from the documentation supplied with your equipment.
No tier-1 source was found for this value. Take it from the documentation supplied with your equipment.
LET EACH LAMP BECOME COOL BEFORE YOU TOUCH IT.
A halogen lamp operates at a very high temperature. Contact with a lamp that is not cool can burn you.
- Open the first fixture as its documentation specifies.2mReport a problem with step 1, Change the lamps
- Some fixtures have a lens that turns.
- Some fixtures have small screws in the ring.
- Do not use force on a fixture that does not open.
- Remove the lamp from the fixture.1mReport a problem with step 2, Change the lamps
- A lamp with two pins pulls straight from its holder.
- A lamp with a wedge base also pulls straight from its holder.
- Read the type and the wattage from the base of the old lamp.2mReport a problem with step 3, Change the lamps
- The marks are small. Use a flashlight.
- Keep the old lamp until the new lamp operates correctly.
- Read the maximum wattage from the label on the fixture.2mReport a problem with step 4, Change the lamps
- The label is usually inside the fixture or on its stem.
- Do not install a lamp above this maximum.
- Write the fixture, the lamp type and the wattage on paper.1mReport a problem with step 5, Change the lamps
DO NOT TOUCH THE GLASS OF A NEW HALOGEN LAMP WITH YOUR FINGERS.
Material from your skin stays on the glass. The lamp then fails long before its rated life.
- Hold the new lamp with a clean cloth.<1mReport a problem with step 6, Change the lamps
- Clean gloves are also satisfactory.
- This rule applies to every halogen lamp.
- Put the new lamp into the holder.1mReport a problem with step 7, Change the lamps
- Align the pins with the holes of the holder.
- Do not use force.
- Close the fixture.2mReport a problem with step 8, Change the lamps
- Make sure that the seal is in its groove.
- Water in a fixture destroys the lamp and the holder.
- Do the same for each remaining fixture.
Add up the load and compare it with the transformer
Estimated 16 min to 40 min
No tier-1 source was found for this value. Take it from the documentation supplied with your equipment.
No tier-1 source was found for this value. Take it from the documentation supplied with your equipment.
ADD THE VA VALUE OF EACH LED FIXTURE, NOT ITS WATTAGE.
Hinkley says the VA value gives the load on the transformer. The wattage value gives only the energy cost.
- Write the value of each fixture in the system on paper.5mReport a problem with step 1, Add up the load and compare it with the transformer
- Use the VA value for a fixture with an LED module.
- Use the lamp wattage for a fixture with a halogen lamp.
- The documentation for the fixture gives the VA value.
- Add the values to get the total load of the system.3mReport a problem with step 2, Add up the load and compare it with the transformer
- Include every fixture on every cable run.
- Include a fixture that has no lamp at this time.
- Read the wattage rating from the label on the transformer.2mReport a problem with step 3, Add up the load and compare it with the transformer
- The label is on the case or inside the door.
- Write the rating with the total load on the same paper.
- Compare the total load with the rating of the transformer.2mReport a problem with step 4, Add up the load and compare it with the transformer
- Kichler says the total VA must not be more than the rating.
- Hinkley says to keep some capacity for more fixtures later.
DO NOT CONNECT THE TRANSFORMER IF THE TOTAL LOAD IS MORE THAN ITS RATING.
An overload makes the transformer very hot. The transformer can then cause a fire.
- If the total load is more than the rating, remove fixtures from the system.5mReport a problem with step 5, Add up the load and compare it with the transformer
- Disconnect the cable of a fixture at its connector.
- Do the calculation again after each change.
- Speak to a contractor about a larger transformer.
Start the system again
Estimated 16 min to 30 min
Source: Prepping for Installation: Calculating Your Project Load Size · tier 1 · accessed 2026-07-29
No tier-1 source was found for this value. Take it from the documentation supplied with your equipment.
No tier-1 source was found for this value. Take it from the documentation supplied with your equipment.
- Connect the plug of the transformer to the receptacle.<1mReport a problem with step 1, Start the system again
- Set the switch or the timer of the transformer to ON.<1mReport a problem with step 2, Start the system again
- Examine each fixture in the system.5mReport a problem with step 3, Start the system again
- Do this examination after dark.
- A lamp at the end of a long cable run is frequently dim.
- If a fixture is dim, measure the voltage at that fixture.5mReport a problem with step 4, Start the system again
- Set the multimeter to the AC range.
- Touch one probe to each of the two conductors at the fixture.
- Kichler says to measure the voltage and not to trust the calculation.
- Compare the measurement with the minimum in the documentation for the fixture.2mReport a problem with step 5, Start the system again
- Kichler gives a minimum of more than 10 V at the last fixture.
- Hinkley gives a range of 10 V to 15 V for its own drivers.
- The documentation for your own fixture is the correct source.
- Write the date, the lamp types and the total load in your records.3mReport a problem with step 6, Start the system again
- Keep this record with the documentation for the transformer.
Terminology
This page uses one term for each item and holds it throughout, as ASD-STE100 requires. Equipment sellers and other guides use the names below for the same parts.
- low-voltage landscape lighting
- Also called: landscape lights, garden lights, yard lights, path lights, outdoor low voltage lighting, 12v garden lighting
- transformer
- Also called: power pack, landscape lighting transformer, 12v transformer, driver, the box the lights plug into
- lamp
- Also called: bulb, light bulb, MR16, wedge base bulb, bi-pin bulb, landscape bulb
- volt-ampere
- Also called: VA, wattage, load, draw, how many watts
- voltage drop
- Also called: dim lights at the end, last light is dim, long run, cable loss
When to use a professional
Do not open the case of the transformer. Do not remove a cover from the transformer. Do not disconnect the cord of the transformer from its case. A licensed electrician must do all work inside that case.
Stop if the case of the transformer is very hot. Stop if the transformer has a smell of burnt material. Stop if the cord or a cable has damage. Disconnect the plug and speak to a licensed electrician.
Speak to a licensed electrician about the receptacle if it has no protection from a ground fault. Speak to a landscape lighting contractor about a new cable run, a larger transformer or a cable below the ground. This page covers lamps and load only, and it ends there.
Common questions
How many lights can I run off my landscape lighting transformer?
As many as fit under the rating printed on that transformer, and no page can tell you what that rating is. Kichler states the rule directly: add the VA of every fixture, and the total VA of the system should not exceed the wattage value of the transformer. Hinkley says the same thing and asks you to leave some spare capacity for fixtures you add later. So the arithmetic is yours to do and the ceiling is on your own label. Do it before you buy fixtures rather than after.
Is there an 80% rule for landscape lighting transformers?
You will see it repeated almost everywhere, and this page does not use it. Neither manufacturer whose own technical guidance we could open publishes a percentage at all: Kichler states a ceiling of 100 percent of the rating, and Hinkley asks for unquantified headroom. The 80 percent figure is generally attributed to a trade association rather than to an equipment maker, and a value that exists only in restatements is unverified by definition however sensible it sounds. If your transformer's own instructions state a percentage, that instruction wins over anything on this page. If they do not, size to the published ceiling and stop guessing at margins nobody has stood behind in writing.
The lights at the far end of the run are dim. What is wrong?
Almost always voltage drop along the cable. Kichler publishes the arithmetic — voltage drop equals two times the cable length times the total VA on that run, divided by a cable constant — and says the voltage arriving at the end fixture should come out above 10V for the fixture to work properly. Hinkley approaches the same floor from the other side and says its LED drivers accept 10VAC to 15VAC. Kichler's own advice is not to trust the sum: it recommends confirming with a voltmeter, which is why this page has you measure rather than calculate. The fixes Kichler names are moving to a higher voltage tap or taking fixtures off that run, and both of those are cheaper than rewiring.
Why does my LED fixture list both watts and VA?
Because they answer two different questions and only one of them sizes your transformer. Hinkley explains it plainly: the wattage is the electricity the LED actually consumes, while the VA is the power the supply has to deliver in order to run it, because the driver converts 12 volt alternating current to direct current and that conversion costs something. Add up the VA to size the transformer. Add up the watts to work out the running cost. Adding up watts and calling it the load is the most common way a system ends up overloaded on paper that looked fine.
Can I put LED lamps in fixtures that came with halogen?
Sometimes, but check before you buy a boxful. The load calculation changes when you do it, because a halogen lamp is rated in watts and an LED fixture or retrofit lamp is rated in VA as well, and the two are not interchangeable in the sum. Some older transformers and some timers also behave differently with a much smaller load than they were designed for. The documentation for your transformer and for your fixture is the place that answers this, and this page will not generalise across equipment it cannot see.
Do I have to touch any house wiring for this job?
No, and if you find yourself about to, stop. The whole procedure runs on the 12 volt side of the transformer, and the only thing you do on the supply side is pull the plug out of the outdoor socket. Anything inside the transformer case, anything involving the socket itself, and anything that means burying new cable belongs to a licensed electrician or a landscape lighting contractor. Kichler's guidance also expects that socket to be a ground-fault protected one, so if yours is not, that is a conversation to have with an electrician before you think about lamps.
Related procedures
- How do I know which LED bulb to buy? Reading lumens, watts equivalent, color temperature and bulb base size before you shop
- How do I change the light bulb inside my oven?
- How to replace a thermostat and get the wires on the right terminals
- How old is my carbon monoxide detector and when do I replace it
- How to find and record the model and serial number of every appliance in the house
Sources
Every specification on this page is traced to one of these sources. Tier 1 is a manufacturer document, a published standard, or a government safety authority. See Standards for the full tiering rule.
- Tier 1Prepping for Installation: Calculating Your Project Load Size
- Tier 1Choosing the Right Transformer for Your Landscape Lighting Job
- Tier 1How to Easily Install Low Voltage Landscape Lighting
Revision history
Current version 1 · updated 2026-07-29 · next review due 2027-07-29
- v1 · 2026-07-29First draft. Load rule and the greater-than-10V end-fixture figure from Kichler's own technical guidance, corroborated on the 10 V floor by Hinkley's stated 10VAC-15VAC driver range; the VA-against-watts distinction from Hinkley. The run-length derating publishes as consult-the-documentation because neither manufacturer publishes one, and the widely repeated 80 percent rule publishes nowhere because it traces to a trade association and not to an equipment maker.
Corrections to this page are listed in the public corrections log. Reports that are credible and not yet verified are listed in the public errata register, and an open one renders above the step it concerns.
Comments and corrections
Found an error? A correction with a manufacturer source is applied and logged publicly. You can also write to corrections@fixchecklist.com.
Every step above carries its own report control, which tags the report with that step so a correction reaches the right place. For anything about the procedure as a whole — the order of the sections, a step that is missing, something that did not match your equipment — use this: report something about this whole procedure.