Energy-efficient light bulbs can be far from perfect.

CFLs take minutes to achieve full brightness compared with LEDs that brighten instantly, but in tests, one LED was dim and emitted a ghastly, bluish light color, and others couldn't cast light in all directions.

Consumer Reports has identified four light bulb letdowns and ways to prevent them.

Dim bulbs:

Opt for more lumens. Check the lighting facts label on the packages of CFLs and LEDs for the number of lumens. The higher the lumens, the brighter the bulb.

Weird light color:

Choose the right Kelvin (K) number. Light color is expressed by its Kelvin temperature. The higher the Kelvin number, the cooler the light. Those wanting to trim electric bills who prefer the warm light of an incandescent should choose a CFL or LED marked 2700K or so on the lighting facts label.

Unflattering light:

Choose bulbs with a higher CRI. When the colors of things look off, find out the color rendering index of the lightbulbs. CRI indicates how accurately a lightbulb displays colors, and the higher the better. Incandescent bulbs are at or near 100; most CFLs and LEDs Consumer Reports tested are in the low-to-mid 80s.

Early burnout:

Return the bulb to the retailer or contact the manufacturer. You may need the model number or UPC and a receipt. And when buying replacements, be sure the bulbs can be used in existing fixtures. Putting a CFL or LED in an inappropriate fixture can shorten its life.