How to Replace G4 Halogen Bulbs With LED
You can often replace a G4 halogen landscape bulb with a G4 LED without replacing the fixture. The LED must match the socket, operating voltage, available space and enclosure requirements. Your transformer and dimmer must also support the new load. Buy and test one suitable lamp before converting a group of older fixtures.
This guide covers replaceable G4 lamps in low-voltage landscape fixtures. If you are unsure which lamp you have, begin with T3 vs. G4 bulb identification. Fixtures with nonreplaceable integrated LEDs require a different service approach.
Before buying: check these six things
| Check | What to confirm |
|---|---|
| Base | The fixture requires G4; the replacement pins match without modification. |
| Voltage | The measured supply at the lamp stays within its specified input range. |
| AC or DC | The replacement accepts the type of power the system supplies. |
| Size and enclosure | The LED fits with the lens closed and is approved for the enclosed application. |
| Brightness and color | Lumens and color temperature suit the original lighting goal. |
| Transformer and controls | Minimum load, capacity and dimming method support the selected LEDs. |
Choose LED brightness by lumens, not matching watts
Watts describe power use. Lumens describe light output. A 20W halogen replacement does not need to consume 20W as an LED, and there is no single LED wattage that perfectly replaces every 20W halogen installation.
Use the old lamp's published lumens when available, then compare the replacement's output and distribution. The shade, reflector and lens affect how much light reaches the ground. A brighter bare lamp is not always a better path-light result.
For a shopping starting point, the EmeryAllen 2W G4 LED in 2700K is listed at 200 lumens. That is a model-specific output, not a promise that every 2W G4 produces the same brightness. Compare alternatives in our G4 landscape lamp buying guide.
Check the transformer before converting the whole system
An older electronic halogen transformer may require a minimum load that a small group of LEDs does not meet. Symptoms can include flickering, pulsing or failure to start. Check the transformer documentation for LED compatibility and loading requirements; changing lamps cannot correct an incompatible supply.
Lowering the load can also change voltage at the fixtures. A transformer tap that worked with halogen lamps may deliver too much voltage to a particular LED after the conversion. Check voltage at representative fixtures under the new operating load, including nearer and farther fixtures. Do not assume the tap label equals the voltage at every socket.
For example, Brilliance's 2026 G4 EcoStar sheet specifies an 8–14V AC/DC input range. Whether that lamp is suitable depends on actual voltage at the fixture, not simply on calling the overall installation a “12V system.” Follow the sheet and label for the exact revision supplied.
How to change a G4 landscape bulb
- Switch off power and let the old lamp cool. Disconnect the low-voltage system's power before opening fixtures. This is not a guide to modifying the transformer's line-voltage wiring.
- Open the housing as directed. Keep track of seals, screws and lens parts. Look for trapped water, corrosion or cracked components.
- Remove the old lamp and inspect the socket. Follow the fixture instructions and avoid twisting or forcing the pins. A loose, burned or corroded socket needs attention before a new lamp goes in.
- Seat the LED fully and securely. Align both pins with the correct holes. Hold the lamp by its supported body without crushing exposed components. Do not bend pins to compensate for a wrong base.
- Reassemble the fixture. Restore seals correctly and make sure the lens or shade does not press on the lamp. Do not leave the housing open to accommodate an oversized LED.
- Restore power and test. Check startup, steady output and supported dimming. Evaluate the light after dark before converting the remaining fixtures.
If the new G4 LED flickers, check connections first
Start with a lamp that is not fully seated, a loose socket or a failed weatherproof wire connection. Turn power off before inspecting. Outdoor wire nuts or other splices can pull apart or lose contact; a new lamp will not repair that fault. A failing LED lamp is another possibility.
If only one fixture misbehaves, inspect that fixture and its connection, and try a known-good compatible lamp. If a whole group flickers, look for a shared connection problem, unsuitable transformer loading or incompatible controls. This pattern helps narrow the investigation but does not prove the cause.
See our landscape-light flickering troubleshooting guide and waterproof landscape connection guide for the next checks.
Can the replacement LEDs use the existing dimmer?
Only when the lamp, transformer and dimmer are compatible as a system. “Dimmable” on a bulb does not mean every control will work. Confirm the supported dimming method and load range, then test startup and stability at the lowest setting you intend to use.
G4 LED replacement questions
How much power can a conversion save?
If ten 20W lamps are replaced by ten suitable 2W lamps, lamp power falls from 200W to 20W—a 90% reduction. That example excludes transformer losses and assumes the LEDs provide the desired lighting; it is not a universal brightness equivalency.
Can I mix G4 halogen and LED lamps?
Sometimes, subject to the transformer, controls and lamp ratings. Check the mixed load and voltage rather than assuming the remaining halogens solve compatibility problems. Different lamp colors and distributions may also look uneven.
What if the new bulb fits but will not light?
With power off, check seating and connections first. Then verify the lamp is suitable for the supply's voltage and AC/DC type. Have a qualified installer investigate persistent electrical faults.
Ready to compare replacements? Shop G4 LED bulbs and T3 replacement lamps and confirm the specifications against your fixture before ordering.
Not sure the old capsule is G4? Compare its specified base with GY6.35 LED bulbs before buying. They are a separate base family, and some GY6.35 models are not recommended outdoors. Choose only the format and application rating required by your fixture.
Sources and specification notes
Manufacturer information checked September 30, 2026. Match the exact lamp model and current installation instructions before ordering.
- Atlantic Lighting