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Achieving NET Zero with Off-Grid vs Grid-Tied Solar Lighting

SEPCO 8/7/14 9:30 AM
Achieving NET Zero with Off Grid vs Grid Tied Solar Lighting

Companies today are looking for ways to improve their energy efficiency, lower their costs and increase their sustainable practices in their business model. One of the most effective ways for a company to complete all three tasks is to look for NET Zero solutions. NET Zero is when a business or home uses an equal amount of power that it produces on a yearly basis. There are times when a building may use more than it produces at one point of the year; however, it averages out when the building produces more energy than it uses.


Lighting is a huge part of the energy usage of a business; however, there are options to help achieve NET Zero when looking at exterior lighting utilizing solar lights. There are two main types of solar lighting systems that can help achieve a NET Zero application. The first is off-grid solar lighting systems that utilize no power from the grid. The second is grid-tied solar lights that feed the grid during the day and use the power from the grid at night.

Off-Grid Solar Lighting

PMRF Off Grid Solar Lighting


With off-grid solar lighting, the solar panel is sized to charge a battery bank during the day that is large enough to feed the lights all night. The solar power system is determined by the light fixture Amps, the amount of sun in the worst-case scenario (typically winter), the run time required, and the amount of battery backup that is required for that area, a minimum of five days autonomy is typical in a good system. These systems do not rely on the grid power and are completely NET Zero from installation.


In areas with very little sun in the winter, there are restrictions on what wattage lamp can be used. High-powered LEDs will require much larger solar arrays and battery banks in the northern areas, making the systems costly for the initial purchase. This can be reduced by reducing the run time of the system (say only 2 hours after the business closes and then on again an hour or so before the business reopens). Working with a solar lighting professional or a lighting designing company can help you find the best solution to fit your budget and provide the necessary lighting requirements for your application.

Grid-Tied Solar Lighting

Grid Tied Solar Lighting


With grid-tied solar lighting, the solar panel is sized to the average sun hours and does not include a battery bank. The solar feeds the grid during the day, and the grid runs the light fixture at night. There are still sizing constraints with this type of system to achieve NET Zero. The solar panel needs to be sized to provide enough power that it equals the usage of the lamp. A large 250 Watt Metal Halide lamp will require a much larger solar power system than a 90 Watt Equivalent LED fixture. LED switch-outs are recommended in grid-tied solar lighting applications.


These systems are much less costly than off-grid solar lighting systems and have a quick ROI, but are not a good option in areas that do not have grid power already installed or easy access to grid power. If there is no electricity currently at the site, off-grid solar light systems are the better solution since there will be no trenching of the area (especially roadways and parking lots) and the expensive drop-down and cables required to run the electricity to the area.


Each option has its benefits to help a business achieve NET Zero certification on their new or updated facilities. Working with a solar lighting company that understands your needs will ensure that you have a system designed to specifications and will provide a great ROI and long life.