By Stan Walerczyk
This is a follow-up to our previous article on lighting controls and which ones are best for specific situations.
This column compares lighting only, basic controls only, advanced controls only, lighting with basic controls and lighting with advanced controls in a typical private office. You can decide what is best for you.
EXISTING TYPICAL PRIVATE OFFICE
- 10′ x 12′
- Two 2×4 18 cell parabolic troffers
- Each with three basic grade fluorescent 32W F32T8s and generic standard ballast factor (BF) ballast, which consumes 90W
- Building time system set at maximum annual hours of operation at 3500
- Office worker does an average job manually turning off lights when leaving, so 3000 hours a year with the manual switches
- KWH rate is $0.12 (national average)
- $ 64.80 Annual lighting consumption
- There is already good LED task lighting, which will be kept
- Good size south facing window
- With the sun’s intensity and glare the window blinds are closed most of the time
Although these products may qualify for rebates, which would improve financial return, rebates are not included.
|$260.00||Parts and labor for 2 20W 5000K LED troffer kits|
|$14.40||Annual electrical consumption|
|$50.40||Annual electrical savings|
|5.2||Year payback without rebate|
This could also be done by retrofitting each troffer with 1 high lumen 32W F32T8 850 lamp, 71 BF high performance program start ballast and upscale kit for about $110 parts and labor. Wattage would be 25.
BASIC GRADE CONTROLS ONLY
|$70.00||Install wall mounted occupancy sensor|
|16%||Estimated energy savings, based on California Energy Commission Database for Energy Efficient Resources (CEC DEER)|
|6.7||Year payback without rebate (if controls are mandated, there may be no rebate)|
ADVANCED CONTROLS ONLY
|$140.00||Install advanced controls|
|25%||Estimated energy savings, based on California Energy Commission Database for Energy Efficient Resources (CEC DEER)|
|$ 16.20||Annual savings|
|8.6||Year payback without rebate (if controls are mandated, there may be no rebate)|
LIGHTING & BASIC CONTROLS
|$330.00||Parts and labor|
|$ 52.70||Annual electrical savings, which controls savings are based on 40W lighting|
|6.3||Year payback without rebate|
Based on getting the lighting down to 40W, the occupancy sensor would only save $2.30 per year, which is a 30 year payback, which is probably infinite because the sensor will probably not last that long.
LIGHTING & ADVANCED CONTROLS
|$400.00||Parts and labor|
|$ 54.00||Annual electrical savings|
|7.4||Year payback without rebate|
Based on getting the lighting down to 40W, the advanced controls would only save $3.60 per year, which is a 39 year payback, which is probably infinite because the controls will probably not last that long.
PAYBACK IN YEARS COMPARISON
|6.7||Basic controls only|
|8.6||Advanced controls only|
|6.3||Lighting & basic controls (30 years for the occupancy sensor assistance)|
|7.4||Lighting & advanced controls (39 years for the advanced controls assistance)|
Paybacks and other financial returns would vary depending on other parameters, which you could do for your projects. But even if the percentage savings from basic or advanced controls were doubled, their paybacks and other financial returns would still be terrible when done with lighting.
Although advanced controls are often not that good saving energy with lighting, they can provide some very significant benefits, including:
- Signaling exact wattage usage
- Providing cumulative hours of operation for LED products
- Notifying that certain lighting fixtures are not working properly
- Turning on the next hibay for fork lift drivers that motion sensors will not trigger in time
- Improve security
- Proper billing various tenants in master metered buildings
- Informing how and when various rooms are being used
- Interior GPS
- Measuring carbon dioxide and humidity
- And what is probably most important, optimal dosing of light intensity and spectrum at different times of the day for various tasks to improve circadian rhythms, alertness, mood, performance, sleep, etc.
Even though some ‘experts’ are recommending lighting for automatic demand response (ADR), let’s do a comparison at 10% reduction with .5 watts per square foot (WSF) lighting, electric car charging stations and HVAC.
- An addressable 3KV EV charger sheds the demand equivalent of 3000/.05/.1 = 60,000 square feet (SF) of lighting
- Vehicle batteries could be used to feed into the grid when necessary.
- An addressable 5 ton HVAC unit at 1KW/ton sheds the demand equivalent of 5000/.05/.01 = 100,000 SF of lighting
- 1 ton HVAC handles about 400 SF.
- Based on one light fixture per 80 SF, there would be 750 lighting fixtures in 60,000 SF and 1250 lighting fixtures in 100,000 SF.
- It will cost a lot more to connect dimming and demand response controls to 750 or 1250 lighting fixtures than to one electric car charger or one HVAC unit.
- Even if lighting is 1.0 WSF, which would be 375 or 625 fixtures, car chargers and HVAC would still be much more cost effective for automatic demand response.
If you have any comments on this column, please let me know at firstname.lastname@example.org.
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