By Stan Walerczyk
First of all, let’s define smart lighting. It is efficient lighting with advanced wired or wireless controls.
Several end-customers really like the WOW factor and varied benefits of smart lighting, including improved security, improved billing of various tenants in master metered office buildings, recommended light and CCT for Human Centric Lighting, etc. Distributors and contractors can supply these systems to these customers. If you are not already aware, many of these systems can be expensive to buy, install, commission and keep running properly.
But smart lighting is often not cost effective just to save energy with today’s high performance LED and incumbent lighting systems.
There are two reasons for this. One is that high performance LED and incumbent lighting technologies are so efficient and use so little wattage even at full output, that there is not very much energy for any automatic controls to save. The other is that lighting is usually two times more cost effective than controls to save energy.
It is usually good to reduce wattage first with lighting and then check if controls are cost effective. For X amount of money it is usually better to do more square footage with basic high performance lighting than a smaller area with smart lighting. Basic high performance lighting is less expensive, easier to install, easier to commission and easier to keep operational.
Here is a good private office example:
- 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
- Building time system set at maximum annual hours of operation at 3500
- Office worker does a fairly good job manually turning off lights when leaving, so 3000 hours a year with the manual switches
- KWH rate is $0.15
- Annual lighting consumption is $81
- 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
Both high performance fluorescent and LED lighting retrofits can be cost effective even without rebates.
- Each troffer can be retrofitted with one high performance 32W 5000K F32T8 lamp, high performance .71 BF program start ballast and upscale kit
- $115 parts, labor and disposal
- $22.50 annual electrical consumption
- $58.50 annual electrical savings
- $230 parts, labor and disposal
- 3.9 year payback without rebate (would be better with rebate)
- Each troffer can be retrofitted with fixed 20W 5000K troffer kit
- $130 parts, labor and disposal
- $18 annual electrical consumption
- $63 annual electrical savings
- $260 parts, labor and disposal
- 4.1 year payback without rebate (would be better with rebate)
Before we deal with advanced controls, let’s look at an inexpensive wall mounted occupancy sensor.
- 16% energy savings, based on Database for Energy Efficient Resources (DEER)
- $3.20 annual savings based on averaged $20 consumption
- $80 installed cost
- 25 year payback without rebate
- Probably infinite payback, because sensor will probably not last 25 years
Even if an advanced control system could save $6.40 per year, which is 32%, it would probably cost $160 per room including the percentage of the total cost. So the payback would be the same 25 years, which would probably be infinite, because the system would probably not last 25 years.
As mentioned in previous columns, advanced controls can provide additional benefits, such as improved security, proper billing of various tenants in master metered office buildings, optimal light intensity and CCT for Human Centric Lighting, etc.
Unless the end-customer really wants other benefits of smart lighting, distributors and contractors can usually provide less costly and simpler to install and monitor basic lighting systems to save energy. This is important, because saving energy is usually most important.
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