The Myth That Motion Sensors Kill LED Bulbs (And Why Physics Disagrees)

I understand the hesitation. You’re standing in the aisle of the hardware store, or staring at a checkout cart with a Rayzeek sensor switch in it, and a nagging voice in the back of your head says: “Turning the lights on and off constantly is going to blow the bulbs.”

I know that voice because I used to have it. Back in 2013, I managed maintenance for a large condo complex in Arlington, VA. The HOA board, in a fit of budget-consciousness, installed motion sensors in every hallway and paired them with the cheapest spiral CFL bulbs they could find. Within three weeks, I was on a ladder every single day. The rapid cycling cooked the cathodes in the fluorescents; the hallways turned into a disco of flickering pink and orange light, and the residents were furious. I replaced nearly 200 bulbs that month. It was a disaster.

But that was 2013. That was fluorescent technology. If you are still applying that trauma to modern LEDs, you are burning money to solve a problem that no longer exists.

Lighting physics has flipped. With Compact Fluorescents (CFLs), starting the arc was the most stressful event in the bulb’s life. With LEDs, starting is easy. It is running that kills them. If you want to understand why your motion sensor is actually the best friend your LED investment has, stop looking at the light switch and look inside the bulb.

Anatomy of a Failure: Heat vs. The Switch

To see why the "cycling myth" fails for LEDs, look at what actually breaks when an LED "burns out." The Light Emitting Diode itself—the tiny chip that produces light—is incredibly durable. It doesn't have a filament to snap like an incandescent, and it doesn't have a cathode to wear out like a fluorescent. Theoretical bench tests show the chips themselves can last 100,000 hours or more.

So why does the box say 15,000 hours? And why do they fail in commercial office buildings in three years?

It’s the driver. The driver is the little circuit board tucked into the base of the bulb that converts your wall’s 120V AC into the low-voltage DC the LED needs. On that circuit board, there is usually an electrolytic capacitor filled with a liquid electrolyte. When the bulb runs, it generates heat. In a recessed can light or an enclosed fixture, that heat has nowhere to go. The internal temperature of the driver can easily hit 85°C (185°F).

At those temperatures, the electrolyte in the capacitor cooks off. It dries out. When it dries out, the driver fails, and your light goes dark.

I saw this clearly during an energy audit for a commercial facility in Baltimore a few years back. The facility manager, a guy named Dave, insisted on leaving the T8 LED tubes in the stairwells on 24/7 because he was convinced switching them would hurt them. We pulled the logs and measured the lumen output. The 24/7 lights were fading twice as fast as the sensor-controlled lights in the basement. The constant heat was degrading the phosphors and drying out the capacitors.

The lights on the sensors? They got to rest. Every time the sensor timed out and turned off, the bulb cooled down. That cooling period extended the life of the electronics significantly. By trying to "save" the bulbs by leaving them on, Dave was actually accelerating their death by heatstroke.

There is one exception to this rule: junk hardware. This logic holds true for decent quality gear—Cree, Philips, Feit, or the commercial stuff I install. If you buy the absolute bottom-barrel, unbranded bulbs from a random online bin where the unit cost is eighty cents, all bets are off. Those bulbs often use components so cheap they might fail if you look at them wrong. But for any bulb built to a standard, heat is the enemy, and the "off" state is the cure.

The "Inrush Current" Myth

Then there's the fear of the "surge." The idea is that every time you flip the switch, a massive spike of electricity hits the bulb, damaging the electronics. This is a classic example of a little bit of knowledge being dangerous.

Yes, there is an "inrush current" when a device turns on. Capacitors need to charge up. But modern LED drivers are designed with "soft start" features that dampen this spike. They don't slam the full load instantly; they ramp it up in milliseconds—too fast for you to see, but slow enough to protect the circuit.

Furthermore, modern sensor switches like the Rayzeek RZ021 series or similar commercial-grade sensors use better internal relays than old mechanical toggles. Many use "zero-crossing" technology, which waits to close the circuit until the AC sine wave is at zero volts. This minimizes the electrical stress to almost nothing.

I ran a pilot test in my own workshop to prove this to a skeptical client. I rigged up a sensor switch to a test bench with a mix of LEDs and set the timeout to 15 seconds—the most aggressive cycling you could realistically imagine. I let it run for a month. Thousands of cycles. Not a single failure. The soft-start drivers and the clean switching meant the stress was negligible compared to the thermal damage of leaving them on.

The ROI Smackdown

Let’s pretend for a moment that I’m wrong. Let’s assume the ghost of the CFL era is real and using a motion sensor does shorten your LED bulb’s life by 10%. Does it matter?

We have to look at the math, because physics doesn't care about your feelings, and neither does your wallet.

An average 10W LED bulb costs about $3. Electricity in the US averages around $0.15 per kWh (and much higher in places like California or the Northeast).

If you leave that 10W bulb on for 10 hours a day when no one is in the room (common for bathrooms, pantries, or garages), you are wasting 100 watt-hours a day. Over a year, that’s 36.5 kWh. 36.5 kWh x $0.15 = $5.47 wasted per year, per bulb.

If a motion sensor saves you that $5.47 a year, in five years you have saved over $27. The bulb cost you $3.

Even if the sensor caused the bulb to explode every two years (which it won’t), you could buy a brand new bulb with your energy savings and still come out ahead. The fear of "wasting" a $3 bulb is causing people to waste $30 in electricity. It is the definition of penny wise and pound foolish.

When Things Actually Go Wrong

Compatibility is not magic. While the sensor won't kill your bulb, that doesn't mean every bulb loves every sensor.

If you install a sensor switch and see the lights flickering, or if they glow faintly ("ghosting") when the switch is supposed to be off, you aren't seeing a lifespan issue. You are seeing a leakage current issue. Many motion sensors require a tiny trickle of power to stay "alive" and watch for motion. If you don't have a neutral wire at the switch box, the sensor pulls that trickle through the bulb.

Old incandescents didn't care about this tiny current. But efficient LEDs might try to light up with it, causing that ghostly glow or a repetitive flicker. This is why I always recommend sensors that require a neutral wire if you can wire them, or ensuring you buy bulbs specifically listed as compatible with "no-neutral" dimmers. The switching isn't killing the bulb. The electrical loop just isn't closed properly.

The Verdict

If you are holding onto the habit of leaving lights on to "save the bulb," let it go. That rule died with the fluorescent tube.

In the LED era, heat is the killer. The cooler you keep your electronics, the longer they last. A motion sensor ensures your lights are off—and cool—whenever you aren't using them. It extends the life of the driver, saves you significant money on your utility bill, and removes the human error of forgetting to flip the switch.

Don't buy the cheapest bulb on the shelf, check the wiring requirements for your switch, and let the automation do the work. Your wallet will thank you.