Selecting a light system is one of the most difficult capital expense decisions for greenhouses. While there are many considerations (including lifespan, maintenance, warranty, installation costs, etc.), two of the biggest factors are the upfront cost of the lighting fixtures and the annual electricity cost to operate lights. In this article, I’ll describe a simple spreadsheet tool I developed to estimate lighting fixture upfront costs and electricity costs based on some information. The calculator tool was developed as part of the USDA Specialty Crop Research Initiative, Project LAMP (lighting approaches to maximize profit), and is available here.
In the calculator tool, you will provide inputs about your crop/greenhouse, such as target light intensity, the area you will be lighting, and your cost of electricity per kilowatt hour (kWh). You will also need to supply some information that you can obtain from a lighting supplier (cost for lighting fixture, photosynthetic photon efficacy, and power consumption). A helpful resource to identify possible lights is also the Design Lights Consortium (DLC) Qualified Product List. DLC is a third-party certifier for horticultural lights that meet certain standards for efficacy (energy efficiency), operating hours, and warranty. Many utility companies require fixtures to be listed by the DLC to qualify for energy efficiency incentives.
The underlying math behind the calculator tool is pretty straightforward, and you can read all about it in a previous eGro Alert here. Okay, first download a copy of the spreadsheet tool by accessing the link here and then clicking on “File” and “Download a Copy” on your computer. After downloading the Excel Spreadsheet and opening it, you may need to click “Enable Editing” at the top so you can input your own data.
The yellow highlighted boxes are information that you will need to input. A few pieces of information you will need to get directly from the lighting supplier 1) the power consumption of the fixture in Watts, the Photosynthetic photon efficacy (PPE) in µmol/J (a measure of light output per unit energy, higher is better), and the cost of the individual light fixture.
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