The Myth of the 1,000-Hour Lightbulb Conspiracy

The story you've heard is wrong. In 1925, lightbulb manufacturers did collude to standardize lifespans at 1,000 hours. They did test each other's products. But the reason wasn't to force you to buy more bulbs. It was to stop a race to the bottom where bulbs lasted longer but were terrible at their job.

A tungsten filament's temperature determines everything: brightness, color, and lifespan. The hotter the filament, the more efficient and whiter the light. But tungsten melts at 3422°C, and the sun's surface is ~5700°C. You can't run a filament that hot. Even at lower temperatures, the filament slowly evaporates and deforms. The trade-off is brutal: a small increase in temperature yields orders of magnitude better efficiency, but dramatically shortens lifespan.

Consider the famous Centennial Bulb in Livermore, California. It's been burning for over 120 years, but it draws only 4 watts and is dimmer than a night light. It was likely a manufacturing defect with high resistance, sold as a night light because it was useless for illumination. That's what you get when you optimize for lifespan alone.

The Physics: Why Longer-Lasting Bulbs Are Worse

Early handmade bulbs were expensive, so they were optimized for long life. But they produced a dim, reddish light. Once automated production made bulbs cheap, it made sense to optimize for efficiency. At $0.10/kWh, a 60W bulb consumes $6 of electricity over 1,000 hours. The bulb itself costs $3. A longer-lasting but less efficient bulb would cost more in electricity than it saves.

The cartel's standard wasn't about making bulbs last 1,000 hours; it was about preventing manufacturers from making bulbs that lasted 2,000 hours but were dimmer and less efficient. Consumers couldn't tell the difference because packaging uses input power (watts) as a proxy for brightness. Two "60W" bulbs could have wildly different light output. The cartel enforced a baseline to protect consumers from misleading products, even if their motives also included price fixing.

Modern Lamps: Fluorescent and LED

Instead of making tungsten bulbs better, manufacturers developed entirely new tech. Fluorescent and LED lamps don't use a wire at the edge of melting, so they can be both efficient and long-lasting. But they still face trade-offs.

Take "Dubai lamps" — LED filament bulbs with four times the diodes, each running at a quarter power. They achieve 200 lm/W versus the usual 100 lm/W, but they're more expensive to make. The real failure mode in LED bulbs isn't the diodes; it's heat damage to the power supply's input smoothing capacitor. Filament-style LEDs can't dissipate heat well, and the capacitor sits in the base. Dubai lamps run cooler because they use less power, but they still run hot.

Specialized Lamps: Different Trade-offs

Not all lamps need to last long. Photography uses "photoflood" bulbs that last only a few hours but produce a truly white light. Indicator lamps are designed for 100,000 hours because they're hard to replace. The right lifespan depends on the use case.

The Real Lesson

Planned obsolescence exists, but lightbulbs aren't a good example. Every product is a bundle of compromises, and consumers often value the wrong metrics. The next time you see a product designed to "last longer," ask what else was sacrificed. For developers, this is a reminder that optimizing for one metric (like uptime) can hurt other important ones (like performance).

For Developers: The Trade-off Mindset

This story applies directly to software engineering. When you optimize for one metric, you often sacrifice others. A database that guarantees durability might be slower. A caching layer that improves read latency might use more memory. The Phoebus cartel's standard was a form of "engineering governance" — setting a baseline to prevent harmful competition.

When you're building a system, think about the trade-offs. Don't blindly optimize for metrics that are easy to measure (like uptime) at the expense of user experience. Understand the physical or theoretical limits of your stack, and design accordingly.

Next Steps

  • Read the original article for the full physics: https://maurycyz.com/misc/tungsten/
  • Watch the excellent YouTube video linked in the article.
  • When choosing dependencies, consider the maintenance burden vs. feature set — not just popularity.
  • In your next design review, explicitly list the trade-offs you're making.