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LED Energy Efficiency – LED Lighting Series
LEDs are currently the most energy efficient light sources available. This is because LEDs are more efficient at converting electrical power into light than traditional light sources. LED sources will convert about 25-40% of the watts consumed into light. In comparison, incandescent light sources convert only 5% of the energy into lights. The remaining energy is converted to heat and is wasted (unless your goal is a heater).
The most common reason for choosing LED lighting over incandescent or other types is energy savings. For a household the total wattage saved by converting to LED can be significant. For example in my home I counted 66 light bulbs that were a mix of 40 watts up to 65 watts. The total wattage of these bulbs amounted to 3,680 watts. By upgrading to LEDs the wattage would be reduced to 586 watts; a reduction of ~85%. See chart below for details.
| # bulbs | Type | Incandescent Wattage | LED Wattage | Saving |
| 28 | PAR recessed lights | 65 | 12 | 53 |
| 17 | A19 medium base | 60 | 9.5 | 50.5 |
| 9 | A19 medium | 40 | 6.5 | 33.5 |
| 12 | Candelabra | 40 | 2.5 | 37.5 |
|
Totals |
3680 | 586 | 3094 |
However, energy savings should not be the only consideration in the decision on LED upgrade. The cost of the light bulbs and the hours of usage are also important factors. More information on evaluating LED lighting costs can be found in article “Calculating True cost of Lighting”. In my case, several of the light bulbs are in areas that are used only briefly each day, if at all. In the case of the Candelabras and PAR lights, the cost of the light bulb is big factor. For low usage areas it may be wise to wait until cost of LED bulbs is lower before upgrading.
An additional consideration in energy evaluation is the type of light source the LED will replace. When replacing incandescent lights there is little doubt that LEDs are a better choice due to the significant reduction in wattage consumed. However, if you are replacing compact fluorescent lights the wattage may already be fairly low and the additional reduction with LEDs may not pay back soon enough. For these situations it will often be other factors that decide when to upgrade to LEDs.
Another consideration in energy efficiency is the type of light fixture. Some light fixtures are designed to use special light bulbs and replacement with standard LED bulbs may not provide the same lighting results as before and thus reduce the overall efficiency. One common example is replacing a directional light source with Omni-directional LED source that wastes light, and energy, by sending it in directions where it’s not able to be used as intended.
If you have any question on if LED light sources are right for your home or business please contact McGill’s Repair and Construction at 641-437-1086 for onsite consultation.
Thank You,
David McGill
James McGill
Article written by Tim McGill, editor@Tree Branch Publishing.
Calculating True Cost of Lighting
The cost of a lighting fixture or bulb is often the deciding factor in the decision to select one type of light over another. When reviewing cost do not simply consider the purchase price alone as that does not include potential operating cost.
A complete evaluation includes all costs over the lifetime of the product. This includes purchase price, installation cost, maintenance cost, and operating costs. Many energy efficient products will pay back the initial costs over time by saving money during operation. This is why purchase price alone is not the best indicator.
Let’s look at LED lighting as an example.
Initial Cost – this is the purchase cost of the LED light bulb or fixture and any installation cost required. To simply replace one light bulb for another may not require installation services from a professional but installing a new fixture or retrofitting an existing fixture to work with LED bulbs will. An electrical contractor should be able to provide estimate on installation cost.
Incentives and Rebates – the government and utility companies may offer an incentive or rebate when selecting a lighting system that reduces energy consumption or is more environmentally friendly. The incentive or rebate has a net effect of reducing your cost and should be included in your evaluation.
Energy Cost – this is the electricity cost to provide power to operate the light. Power is measured as wattage, more precisely, per kilowatts (1000 watts). The electric company charges by the kilowatt-hour (Kwh), for example $.12 Kwh (12 cents for one kilowatt used for one hour of time). One (1) 100 watt incandescent light bulb can operate for 10 hours using 1 Kwh of energy. This seems cheap but adds up quickly over time if used daily and with several light bulbs.
Maintenance Cost – this is the cost associated to keep the lighting system operating. Common maintenance items are repairing failed components, replacing light bulbs, or replacing bulbs to maintain a minimum light level[1]. The rated operating hours of the light bulb is a good indicator of how often the bulbs will need replaced.
Cost Calculation
Let’s compare replacing fluorescent bulbs with LED bulbs in troffer light fixture.
|
Fluorescent linear bulbs |
LED linear bulb |
|
| Total Wattage |
128 W |
58 W |
| Purchase cost1 |
$ 12 |
$ 96 |
| Installation cost |
$ 20 |
$ 20 |
| Rebate2 |
$ 0 |
$ -28 |
| Total Initial Cost |
$ 32 |
$ 88 |
| System life |
10 years |
10 years |
| Energy Cost3 |
$ 460 |
$ 200 |
| Lamp Life1 |
6.67 years |
13.34 years |
| Maintenance Cost4 |
$ 32 |
$ 0 |
| Total Operating Cost |
$ 492 |
$ 201 |
| Total Lifetime Cost |
$ 524 |
$ 289 |
- Philips 4ft T8 32-watt soft white fluorescent bulb, Model 409433, $29.97 per 10-pack, 2950 lumens, 20,000 hour life.
Philips 4ft T8 14.5-watt (32-watt equivalent) InstantFit direct replacement LED linear bulb, Model 433060, $237.22 per 10-pack, 1600 lumens, 40,000 hour life.
Pricing and product data from Home Depot website. - Alliant Energy offers rebate to businesses for replacing fluorescent lights with LED lights at 40 cents per watt saved.
- Assumes 3000 hours per year (equal to ~8 hours per day/7 days per week or ~11.5 hours per day/5 days per week) x electrical rate $.12 kwh x wattage (kw) x 10 years system life.
- Maintenance cost includes replacement bulb cost and labor. Fluorescent system requires all lamps to be replacement one (1) time to reach 10 year system life.
Payback Period
What is your ROI, or when does the savings pay for the upfront costs?
First determine the yearly operating savings ($492 – $201 = $291) and then divide by the number of years (10). In this example the yearly savings is $29. The payback period (ROI) is determined by dividing the Initial cost by the Yearly Savings ($88/$29 = 4).
The ROI for above LED linear bulbs is 4 years.
If you have lighting questions or would like to schedule a technician to perform lighting maintenance, please contact McGill’s Repair and Construction at 641-437-1086.
Thank You,
David McGill
James McGill
Article written by Tim McGill, editor@Tree Branch Publishing.
[1] Many light bulbs will produce less light over time as the light bulb reaches its end of life. LED light bulbs may continue to operate for many 1000’s of hours beyond the useful life.
