Buying a Tertill Weeding Robot - Do the Dollars Make $ense?

A bit about Tertill

Tertill lives in your vegetable garden all season long, runs on nothing but sunshine, and weeds every day - rain or shine. It has a list price of $349 and packs a lot of technology into its 8-inch round cheerful green shell. Tertill is solar-powered, has 4-wheel drive, multiple sensors for identifying plants and weeds, a weatherproof casing, string trimmer, Bluetooth®, free Android/iOS app, and proprietary software that controls its navigation, weeding and recharging.

It requires some simple garden modifications, including a barrier, sufficient space between plants to roam, and a relatively flat surface. To get started, simply place Tertill in your garden and press the button! 

It has been validated as an effective way to control weeds by the Cornell University School of Integrative Plant Sciences and the Weed Science Society of America. Compared to other consumer robots, such as vacuums, which can cost up to $1,000 and lawnmowers, which start at around $1,000 and go up from there, Tertill is also a bargain!

Calculating the robot’s ROI

Here at Franklin Robotics, we are driven by data, so to calculate the return on investment (ROI) for Tertill, we used the following methodology to take into account the varying length of the growing seasons across the country:

  1. We chose 29 places named Franklin (for obvious reasons) all across the United States that were in the different USDA plant hardiness zones. Then we looked up each zip code in the Farmer’s Almanac to get the historical first and last frost dates to determine the growing season for that area.

  2. Because Tertill should be placed in the garden before weeds start to sprout in spring and left in until a hard frost to prevent weeds from going to seed, we added 40 days to the published growing season. (Read Changing This One Habit Can Help Decrease Weeds in Your Garden to learn more about your weed seed bank and how to stop making deposits!)

  3. Then we divided the list price ( $349) by the number weeks that the robot would be actively weeding in each zip code to get a weekly cost for using Tertill for one, two, three, and four seasons. We converted to weeks because most gardeners weed at least once a week. Sure, it would have been easier to just divide $349 by 52 to get $6.71 a week, but that calculation is only valid if you live in a climate where you can leave Tertill in your garden all year round. We are engineers, that’s not how we do things! 

The findings

The average number of days Tertill would be weeding was 214 which equals 31 weeding weeks. This means that on average, Tertill "costs"  $11.91 a week if you use Tertill for just one season. Since Tertill's life-span is much longer than one season, the amortized price drops to $5.96 a week if you use Tertill for two seasons, $2.98 a week for three seasons, and a mere $1.49 per week if you use Tertill for four seasons. This is a very cost-effective way to control weeds in your garden compared to hiring a professional landscaper, local teenager, or even your own children to weed your garden once a week. 


Weeding is hated by many, seen as a necessary evil by most, and loved by a few. It is arguably the most onerous and arduous gardening task and can discourage people who don’t have the time or ability to weed from having a garden. Tertill offers a cost-effective, easy, and effective way to control weeds to help more people enjoy the many benefits of gardening.

Here are the specific robot ROI calculations for all of the Franklins:



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