DRAFT - Lighting Cost Calculators

Welcome to our tools page! These tools help growers better understand the supplemental lighting needs in their greenhouses.

Additional Tools

How many light fixtures do I need?

Determine how many lighting fixtures you need for supplemental lighting in your greenhouse with this calculator. To use the lighting fixtures calculator you will need to download the linked file and open it in Excel. For directions and more info…

DLI Interactive Maps

Find monthly averages for Daily Light Integrals (DLIs) for any US location by using this interactive map developed by colleagues at UT and Clemson. For more info…

Determine which tool to use...

‘Unlimited lighting’ calculator

The first, and now probably least useful, calculator. This calculator determines how much electricity is required to reach the target DLI every single day of the year. To do so, a lighting system would need to be designed to provide enough light on even the darkest day of the year. That is an unrealistic scenario, because it clearly would not be cost-effective to design your lighting system for the darkest day of the year. Because of that unrealistic assumption, this calculator does not calculate demand charges, only the cost of the electricity used. Here is a video demonstration of the LAMP Lighting Cost Calculator Web App.

‘Unlimited lighting’ calculator in EXCEL

This tool was developed for greenhouse growers as part of Project LAMP to estimate electricity costs for supplemental lighting. This is the same lighting cost calculator provided above but this version is formatted in Excel. Select the link and download the file to Excel to use the calculator. Provide in the highlighted fields in the ‘Input and Output’ tab your target DLI, greenhouse design parameters and electricity rate. Select a location to get cost estimates or add your own (within the US).

For directions on how to add your own location to the calculator, follow this link: Add a Location to Excel-LAMP Lighting Cost Calculator.

‘How large should my lighting system be’ calculator

With this calculator, users specify on how many days of year they want to be able to reach the target DLI (expressed as a percentage of 365 days). When set to 100%, this calculator is essentially the same as the ‘Unlimited lighting calculator’. But typically, there is no need or desire to reach the target DLI every single day. After entering what % of days you want to reach the target DLI, the calculator will determine the required lighting capacity, and provide a graphical summary of the lighting conditions you can expect in your greenhouse. This lighting system also estimates the demand charge, associated with the use of the lighting system. This calculator is particularly useful for the design of new lighting installations.

‘How often will I reach my target DLI’ calculator

Similar to the ‘Unlimited lighting calculator’, but taking the opposite approach: users specify the capacity of their lighting system, and the calculator will estimate on how many days of the year you can reach your target DLI. The associated electricity costs and demand charge are estimated as well. This calculator is particularly useful for determining how well an existing lighting system meets your needs.

‘How many light fixtures do I need?’ calculator

Use this calculator (© Neil Mattson, Cornell University 2015) to estimate how many light fixtures you need in your greenhouse to meet your supplemental lighting needs. After opening this link, you will need to download the file into Excel for use. Once downloaded fill in your information in the yellow highlighted fields. Do not modify any boxes or go into the pink fields. Note: the placement of lamps should be determined by a lighting professional for light uniformity in the greenhouse. The number of lamps needed may be somewhat more if you want uniform lighting edges of the growing space and to account for spillage of light at the edges.

DLI Interactive Maps – United States

When thinking about supplemental lighting, it is important to know how much sun light you have in your location. Joanne Logan (University of Tennessee) and Jim Faust (Clemson University) developed these interactive maps of the average daily light integrals (DLI) throughout the US. You can find monthly averages for the DLI for any location. Keep in mind that this is the DLI outside. To calculate the DLI inside your greenhouse, you need to know how much of the sunlight is transmitted into the greenhouse. Light transmission depends on the glazing material and configuration of your greenhouse, how old it is, and how clean it is. Transmission can range anywhere from 35% to 80%. Here is a short video on light transmission, produced by the E-Gro team.