Why are LEDs So Energy-Efficient?

You’ve heard that LEDs save you money in the long run. But what makes them so energy efficient? To understand why LEDs are much more energy-efficient than incandescent or fluorescent lighting, you must first understand how different lights work. In this blog, we discuss how LEDs work in comparison to incandescent and fluorescent lights.

How incandescent lights work and why they’re inefficient

Incandescent Lights Waste 90% of Energy as Heat

Incandescent lights are energy wasteful because they produce light from heat. Ninety percent of the energy consumed by an incandescent bulb is heat lost to the surrounding environment. The heat an incandescent light produces might be useful in a cold environment like Alaska but here in Arizona an incandescent bulb just makes your air conditioner work that much harder. 

Most Incandescent Light Is Not Even Visible

In an incandescent light bulb, electricity heats a metal filament until it glows. Thermal energy produces a range of light. The human eye can only see a small range of the light an incandescent bulb produces. And incandescent lights produce more heat than light. The thermal energy escapes into the environment, which you know if you have ever touched a hot bulb.

 incandescent bulb

Incandescent Lights Are Short-Lived

Incandescent lights have a short lifespan (approximately 1,000 hours). Surges of electricity send vibrations through an incandescent filament that eventually cause the light to fail or blow. Although the light would last longer if left on, the additional cost of leaving a bulb on outweighs the cost of replacing a bulb. 

Incandescent Lights Are Non-Recyclable 

Incandescent filaments are difficult to separate from glass, which means you cannot recycle incandescent lights. Paired with the energy wasted, the disposable nature of incandescent lights makes them inefficient and non-renewable. 

Governments Are Phasing Out Incandescent Lights

Governments around the world have passed laws to phase out inefficient incandescent lights in favor of more energy-efficient lighting. The U.S. government passed regulations to phase out incandescent lights effective in 2020 but reversed the law in 2019 due to the high costs of energy-efficient lights. 

How fluorescent lights work and why manufacturers have stopped producing them

CFL bulb

Fluorescent or compact fluorescent lights (CFL) are more efficient than incandescent lights but less efficient than LED. 

Fluorescent Lights Use Mercury to Produce UV Light

Fluorescent lights contain an ionized mercury gas and phosphorus that coats the glass. When electricity stimulates mercury ions, the excited electrons emit ultraviolet light. Ultraviolet light isn’t visible to the human eye. Phosphorus coats the interior of the CFL glass bulb. The ultraviolet light causes the phosphorus coating to glow with fluorescent light. 

Fluorescent Lights Are More Efficient than Incandescent

Like incandescent lights, CFLs produce more heat than light and this heat is lost into the environment. However, fluorescent lights consume 70% less energy than incandescent lights and last 10 times longer (10,000 to 15,000 hours). Their price point, only slightly higher than incandescent lights, makes them an affordable alternative. 

Fluorescent Lights Flicker and Buzz

The process of stimulating mercury ions until they produce UV light and then converting UV light to fluorescent takes a moment. You will notice that a CFL must “warm-up” before it produces light. Some flickering is normal as a fluorescent bulb warms up. 

A fluorescent bulb that flickers persistently may be on a dimmer switch (most CFL lights are not dimmable) or exposed to freezing temperatures. It could be dirty or nearing its end of life. 

Dirty or misaligned prongs can cause fluorescent bulbs to buzz. For some, the flickering and buzzing can be a minor annoyance. For other people, flickering and buzzing can overstimulate, and cause headaches and even seizures. 

Fluorescent Lights Are Fragile and Hazardous

Although they are more efficient, fluorescent lights are more hazardous than incandescent lights. They are easily broken and can shatter into tiny shards from a too-firm grip. CFLs contain mercury, which is dangerous to pregnant women, children, pets, and the environment. You should not dispose of your CFL lights in a landfill. 

You Can Recycle Fluorescent Lights

On a positive note, the raw materials used in CFLs can be recycled. In fact, many state and local regulations require CFL recycling. You can take your fluorescent lights to home supply chains like Home Depot for recycling. 

Manufacturers Are Phasing Out Fluorescent

Although fluorescent lights are recyclable and more efficient than incandescent lights, you’ll notice many fewer CFLs available at your favorite home supply store. Manufacturers are phasing them out in favor of LED lights. 

How LEDs work

LED light bulb

LEDs are the most efficient lighting we have to date. Electricity goes directly into light production, and they produce very little heat.

Simply put, light-emitting diodes (LEDs) are semiconductors that emit light when stimulated by electricity. More scientifically, atoms release light energy when stimulated. 

Energy Stimulates Electrons, Producing Photons

When energy (like electricity) stimulates an atom’s electrons–which move about–they move away from the nucleus of the atom. The electrons release energy as photons (particles of light). The further the electrons move from the nucleus, the more energy the photons contain, and the brighter the light. 

The Diode and Semiconductor Control Brightness and Color

The diode and the semiconductor material control the color and brightness of an LED. The type of semiconductors determines how far the electrons can move from the nucleus. The distance between an electron and the nucleus determines the color of light photons produce. The diode regulates the energy level of the photons, which determines the brightness the photons produce (which is measured in lumen). Different LED semiconductors produce different color lighting from infrared to ultraviolet. 

Residential External Lighting Installation

What makes LED lights so efficient?

Incandescent and CFL lights must first supply power to heat a filament or gas before the light can be generated. The energy supplied to an LED light isn’t lost to heat. LEDs provide power directly to the source of light–the semiconductor. No energy is wasted.

Because LEDs are directional lights, which means they emit light in one direction, unlike incandescent or CFL lights which emit light in all directions. This reduces the need for reflectors or diffusers which can trap light. Directional lighting reduces wasted light and energy. 

Unlike CFL and incandescent lights, LEDs don’t blow out. They are resistant to shock, shaking, and shattering. As a bulb’s lifetime nears its end, the amount of light it produces diminishes. LEDs can last 25 years. (However, LEDs are susceptible to heat, high wattage, and old dimmer switches. For more information about LED vulnerabilities, read our blog LEDs are Divas.)

What makes LEDs so expensive?

LEDs consume 85% less energy than incandescent lights and last 25 times longer, which is why they are so much more efficient. However, the materials and manufacturing that make LEDs so efficient also make them so much more expensive. 

You may have noticed that LEDs look very different from incandescent or fluorescent lights. For one thing, they have strange ribs. While LEDs don’t produce heat like incandescent or fluorescent lights, they do still produce some heat, which is detrimental to the bulb. Built-in ribs–known as fins or a heat sink–disperse the heat. 

LEDs run on DC (direct current) voltage. But AC (alternating current) voltage powers homes, businesses, and most lamps and lighting fixtures. Manufacturers build an AC/DC transformer into LED bulbs so they can replace incandescent lights in existing fixtures. The transformer also monitors incoming wattage, because high wattage is detrimental to LEDs.  


LED bulbs are quickly replacing incandescent and fluorescent bulbs. And for good reason. They are the most efficient light source in the industry. They are energy-efficient superstars that are long-lived and resistant to physical shock, shaking, and shattering. When installed correctly, they can last you 15-25 years and save up to 85% over the cost of incandescent bulbs. 

If you’ve decided to upgrade to LEDs, call a licensed, bonded, and insured electrician like Redline Electric & Solar to install LED fixtures and upgrade your dimmer switches. We install commercial, business, and residential LED lighting, including ceiling fans, can lights, and outdoor or parking lot lighting.  

NABCEP certified Redline Electric & Solar is the best choice for your electrical and solar needs in Arizona. We are a family-owned and operated electrical contracting business, with over 60 years of combined experience. We pride ourselves in our honesty, integrity, and high-quality work. When you choose Redline Electric & Solar, you can be confident that you’ve made the right decision.