LED bi-pin bulb

Both homeowners and business owners are becoming increasingly interested in LEDs for their outdoor lighting – and for very good reasons. In fact, recent studies in the U.S. have shown that lighting accounts for:

  • 9- to 15-percent of an average household’s energy budget, and
  • 20- to 30-percent of an average commercial establishment’s energy budget

With recent advances in technology and increased environmental awareness, outdoor lighting for residential, commercial, and municipal applications is becoming more energy efficient and aesthetically pleasing. Eco-friendly outdoor lighting options including LEDs are now available for use in new-build as well as retrofit projects.

LED = Light-Emitting Diode

LEDs were first developed in 1962 and for many decades were used primarily as indicator lights for electronic equipment. In recent years, LEDs have been increasingly used for holiday lighting because of their extended bulb life, durability, and markedly lower energy costs.

Up until the last two years, LEDs had not been used extensively for exterior architectural and landscape lighting because of two major issues – Color Temperature/Color Rendering Index and directional aiming deficiencies.

Color Temperature

Color temperature is something that is seen with your eye and not felt by the touch of your hand. Color temperature measures the light that can be seen along the visible spectrum – and it is measured in degrees Kelvin. The photo below illustrates how this color temperature can vary between a warm incandescent bulb and a warm CFL bulb, and a cool fluorescent bulb.

An actual color temperature chart is included below illustrating that the “hottest” visible color is red (1500 degrees K) and the coolest visible light is violet at 10,000 degrees K.

Warm white LEDs are available with a correlated color temperature of between 2800K and 3800K. Cool white LEDs have a color temperature of between 4000K and 7000K. Most people much prefer the warm LEDs because they make the landscaping and architecture appear more natural and inviting. For comparison purposes, a low voltage quartz halogen landscape lighting bulb typically has a color temperature of 2800K – and that is the “gold standard” that LEDs are quickly trying to achieve.

Color Rendering Index (CRI)

CRI rates lighting effectiveness on a scale of 0 to 100. The bottom of the scale – zero – is darkness and at the top of the scale – 100 – is equivalent to the noontime sun on a cloudless day. Quartz halogen and incandescent bulbs have CRI’s in the 80 to 92 range, fluorescent bulbs have CRIs above 90, and LEDs currently have a CRI in the 60 to 80 range. The good news is that the quality of LEDs is improving exponentially on an annual basis.

The other issue with LEDs has been with their ability to effectively aim and focus this light from the semiconductor diodes. Fortunately, manufacturers have developed very unique optics that can effectively control the beam spread; e.g., narrow focus (8 – 10 degrees); medium focus (20 – 30 degrees); wide focus (40 – 45 degrees); and very wide focus (90 degrees) are now readily available.

Benefits of Using LED Outdoor Lighting

LED outdoor architectural and landscape lighting offers many benefits for residential/commercial projects:

  • Significant savings on electrical operating costs (up to 80%) and maintenance
  • Provides extremely bright light on a lumens per watt basis
  • Significantly cooler operating temperatures – provides increased safety
  • Superior system reliability
  • Elimination of toxic materials
  • Instant on/full brightness
  • Compact and unique fixture designs
  • Equal brightness levels for all fixtures
  • Negligible stress to home electrical system


LEDs are very, very efficient. While quartz halogen bulbs can provide 10 to 15 lumens per watt, LEDs can produce between 40 and 80 lumens per watt. Further, LEDs convert 90-percent of the energy input into light and only 10-percent is dissipated as heat. Conversely, incandescent bulbs convert only 10-percent of the energy into useful light – and the remainder is dissipated and wasted as heat.


LEDs have an average useful bulb life of up to 50,000-plus hours. For comparison purposes, the regular incandescent bulb has a life of between 750 to 2,000 hours, a quartz halogen bulb has a life of between 2,000 to 5,000 hours, and a fluorescent has a life of up to 24,000 hours.

Lumen Maintenance

Lumen maintenance is a measurement of the decrease in light output over time – and it is used in conjunction with the average LED bulb life discussed above. In fact, the stated average LED-rated life that manufacturers quote is defined as the time to reach the 70-percent lumen maintenance level (L70).

New-Build Applications

LED lighting when incorporated into a design-build process can greatly reduce the need for additional and dedicated landscape/architectural circuits because of the greatly reduced overall power requirements. On the low voltage side of the installation, typically 12-2 gauge direct burial wire is sufficient for most applications. Additionally, fewer circuits are also required which minimizes any disruption to the landscaping.

LEDs are also an excellent choice for off-grid solar lighting installations at homes or community entrances.

Solar Photovoltaic LED Lighting System Genesee

Solar Photovoltaic LED Lighting System Genesee

Retrofit Applications

There are many possible solutions for retrofitting an existing low voltage quartz halogen lighting system to LED. Quartz halogen 20W bi-pin bulbs can be replaced with a 2W LED bi-pin bulb.

LED bi-pin bulb

The low voltage quartz halogen MR16 20W bulb can also be replaced with a 6W LED bulb in a standard landscape lighting bullet fixture. Additionally, the 6W LED bulb can also be used in conjunction with an adapter to replace the 35WPAR36 quartz halogen bulb used in the standard well lights (for uplighting trees, houses, etc.).

6W LED Conversion for 35WPAR36 Bulb

6W LED Retrofit for 20W MR16 Bulb

While LEDs are still more costly than the conventional low voltage quartz halogen systems, their payback period is becoming shorter and shorter as new technology and manufacturing improvements have resulted in decreasing costs.

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