Replace Indoor Incandescent Lights with Compact Fluorescents

The Measure

Replace indoor incandescent lamps with compact fluorescent lamps.


All apartment buildings where incandescent lighting is used in common areas (corridors, lobbies, stairwells, laundry rooms, etc.), and where incandescent light bulbs can be replaced by screw-in compact fluorescent lamps without replacing the fixtures. This can include lighting in dwelling unit fixtures.


  • Elimination of prolonged lamp outages and reduced maintenance costs.
  • Improved lamp light output (four to five times more per watt than comparable incandescent lamps).
  • 75 to 80% reduction in energy costs.
  • Longer rated life (10 to 20 times longer than for incandescent lamps).


  • Replacement of the fixture glass or the entire fixture may be necessary because the screw-in fluorescent lamp and ballast combination is often larger than an incandescent lamp.
  • If fixture replacement cost is $10 or more, the lamp should not be replaced unless it is on for at least eight hours a day.
  • When replacing a compact fluorescent lamp, replace only the lamp. The screw-in ballast/adapter has a rated life four to five times longer than the lamp.
  • Some recessed fixtures may need a reflector to get maximum useable light output.


  • Can be implemented by property manager.
  • Prepare an inventory of lighting fixtures with incandescent bulbs. Include the number and wattage of bulbs per fixture and inside dimensions of the lamp housings (including clearance from socket to glass and inside diameter).
  • Prepare a list of proposed replacements for incandescent lamp watts with fluorescent lamp watts (e.g. 60W incandescent with 13W fluorescent, etc.).
    Lamp Watts
    Lamp Watts
    60 13 (16 with adapter)
    75 18 (20 with adapter)
    100 26 (28 with adapter)
    150 36 (39 with adapter)

  • Compare dimensions of fluorescent lamp assemblies with fixture dimensions.
  • Replace lamps where no fixture modifications are required.
  • Where larger fixture glass can be obtained for $10 or less, replace the glass if necessary.
  • When fluorescent lamps are due for replacement, install new lamps in the existing ballast/adapter bases - ballasts may need to be replaced as well.
  • Replace incandescent lamps with screw-in ballast-adapter bases and plug-in compact fluorescent lamps.
  • Depending on the type of fixture, replacement units may be the straight, double-tube, compact fluorescent type (PL) or the circular type (e.g. GE Circline).


Results in savings can be influenced by:

  • Cost of electricity.
  • Type of electric utility rate structure.
  • Initial and final number of operating hours.
  • Initial and final number of connected lighting fixtures.
Example: Replace 60W incandescent lamp with a 12W compact fluorescent (16W including ballast)

Cost of incandescent lamp - $1

Cost of fluorescent lamp - $5

Cost of fluorescent ballast - $20

Replacement for incandescent bulbs – every 1,000 hours of operation

Replacement for fluorescent lamps – every 10,000 hours of operation

Replacement for complete fluorescent lamp/ballast/adapter units – every 50,000 hours

Annual Consumption and Costs

    Incandescents Fluorescents Saving
1. 24 hours/day operation
(8,760 hours/year)
  Energy Consumption (kWh)
  Energy Cost (@ $0.08/kWh)
  Lamp Replacement Cost
  Total Annual Cost
2. 8 hours/day operation
(2,920 hours/year)
  Energy Consumption (kWh)
  Energy Cost (@ $0.08/kWh)
  Lamp Replacement Cost
  Total Annual Cost

Simple payback – 1.25 years (24 hours/day operation) to 2.5 years (8 hours/day operation)




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