Frequently Asked Questions - Bulbs and LEDs

What is Color Temperature?

Color Temperature is how warm or cool the light looks. Old incandescent bulbs were usually around 2700 Kelvin (K), which is a safe bet if you're not sure what color temperature you want.

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What is High CRI?

CRI stands for Color Rendering Index, which is a measure of the quality of the light compared to sunlight. a CRI of 90 or above is considered high CRI.

For example, flourscent bulbs have a low CRI with gaps in the color spectrum, whereas a high CRI bulb has a fuller color spectrum with fewer gaps. alt text alt text

What do the codes and numbers mean?

One number describes the shape and maximum width of the bulb, and the other describes the base of the bulb. See below.

Bulb Shapes Explained

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The width of a bulb is measured in 1/8" increments. For example, a common A19 bulb indicates a diameter of 19/8" or 2-3/8 inches. alt text

Bulb Bases Explained

There are many different bulb bases. E26 is the most common type. alt text

How do I know what bulb to order?

The common, everyday, regular light bulb shape is A19 with an E26 base. For different kinds of bulbs, look for labels on the base of the bulb or fixture. If there are no labels, reference the Bulb Shapes and Bases explained above.

What do "Equivalent Brightness" and "Watt Equivalent" mean?

It is a measure of brightness, or Lumens.

We are used to describing a bulb's brightness in terms of Wattage, however Watts measure energy use, not brightness. Brightness is measured in Lumens.

For example, a 60 Watt Equivalent LED bulb will only use 9 Watts of energy, but it is just as bright as a 60 Watt incandescent bulb that wastes much of the energy as heat.

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When do I get my bulbs?

Please read the Greenlights Program information.

Still have questions? For fastest assistance not covered in the FAQ, email Greenlights@ecoactionpartners.org. Inquiries to the EcoAction Partners office phone number will be forwarded to this email address, and may be delayed in receiving a response.