The carbon footprint of a light bulb: electricity and CO₂

A bulb gives off no smoke, but the electricity it uses is generated somewhere. How lighting connects to CO₂, how to calculate it and what a lamp’s full life cycle looks like.

There is no smoke next to a light bulb and no smell of fuel, so lighting can seem far removed from climate change. But the electricity coming out of the socket is generated somewhere, often in a power station that burns fuel. That is where a bulb’s carbon footprint begins, and understanding it does not require advanced science.

The link between the bulb and the power station

Every kilowatt-hour of electricity generated releases a certain amount of CO₂. That amount is called the grid emission factor and is expressed in grams or kilograms of CO₂ per kWh. It varies between countries and from year to year, because electricity comes from different sources, such as natural gas, coal, hydro, wind and solar, in different proportions.

On a grid that relies heavily on coal, each kWh carries a large footprint; on a grid with a high share of hydro and renewables, a small one. In Azerbaijan most electricity is produced by gas-fired thermal power plants, with part coming from hydropower and renewable sources.

The calculation is simple

The CO₂ footprint of a bulb during use is:

CO₂ = yearly kWh × grid emission factor

To get yearly kWh, multiply the bulb’s wattage by daily hours and by 365, then divide by 1000. The emission factor can be taken from official energy statistics or international energy reports. Even without an exact factor, a relative comparison is useful: the CO₂ difference between two bulbs is in the same proportion as their kWh difference.

An important conclusion follows. A switch that cuts consumption by 80 percent also cuts the CO₂ from use at that light point by 80 percent. Your carbon footprint and your electricity bill move in the same direction.

The whole life of a lamp

For the full picture, the lamp’s entire life cycle is considered:

• Manufacturing. Extracting raw materials and making the components, glass, plastics and electronics.
• Transport. From the factory to the warehouse and on to the shop.
• Use. The electricity the lamp consumes over the years.
• End of life. Disposal, recycling or landfill.

Life-cycle studies of household lamps tend to reach the same conclusion: most of the carbon footprint falls in the use phase, that is, in electricity consumption. An LED bulb, with its electronic driver and heat sink, is more complex to make than a simple incandescent bulb. But because it uses far less energy and usually lasts much longer, it comes out ahead overall.

Why it matters for the climate

The CO₂ difference from one bulb can look tiny, but lighting runs in millions of homes, offices and streets at the same time. That is why many countries give phasing out inefficient lamps a special place in their energy efficiency policies. For a single household the message is simple: every kilowatt-hour less spent on lighting shows up both on the bill and in the atmosphere.

Not only CO₂

Other factors belong in the environmental picture. CFLs and linear fluorescents hold a few milligrams of mercury inside. They must not go in household waste, and if one breaks, air the room and collect the fragments carefully. Mercury-free LED lamps remove that risk, but they contain electronics too and should be handed in as electronic waste where possible.

Transport is a relatively small share of the total, but a product made closer to the buyer does travel a shorter distance.

Reducing the footprint in practice

For a home or office the most effective steps are:

• replacing long-running incandescent and halogen lamps with LED;
• switching off lights in empty rooms and using sensors and timers in secondary spaces;
• not choosing bulbs brighter than needed and not multiplying light points without reason;
• making better use of daylight;
• disposing of old lamps properly when they fail.

Every one of these steps also lowers the electricity bill, so the environmental and financial benefits coincide.

Enter your own lamps into the site's savings calculator and it will estimate the CO₂ reduction next to the annual kWh figure. The product pages for the Ganja-made Zəfər İşığı LEDs state that the lamps are mercury-free.