Soil moisture sensors for home sprinkler systems, explained
A weather-based smart controller estimates how much water your landscape needs. A soil moisture sensor measures it directly in the root zone. Here's how the technology works, when it's worth adding, and which Colorado utilities will help pay for it.
What a soil moisture sensor does
EPA describes soil moisture-based irrigation controllers (SMSs) as devices that detect the amount of moisture in the ground beneath the landscape and override scheduled irrigation when plants don't need water. They must be able to consistently bypass irrigation at a predetermined setpoint based on the sensor's reading (EPA WaterSense).
In practice, you bury a probe in the root zone of a representative area and set a moisture threshold. When the soil is wetter than the threshold, scheduled watering is skipped. When it dries past the threshold, watering is allowed to run.
EPA says SMSs come in two forms (EPA):
- Stand-alone controllers with soil moisture control built in.
- Add-on or plug-in devices that work with an existing clock-based controller to help it water more efficiently.
Why it matters
EPA estimates that more than 28 million U.S. homes have in-ground sprinkler systems that typically water on a clock-based schedule. Those schedules are often set for the height of the growing season and not adjusted afterward. EPA says installing a WaterSense labeled SMS can save an average home with an automatic irrigation system more than 15,000 gallons of water a year (EPA WaterSense).
What the WaterSense label tests
To earn the WaterSense label, an SMS must be able to consistently prevent or allow irrigation at a preset threshold, and it's independently certified. EPA lists the key performance attributes tested (EPA):
- Function: can it enable or disable irrigation at a range of moisture depletion levels?
- Precision: does it do so consistently at the preset threshold?
- Response to change in soil moisture: does it notice when moisture changes?
- Function after freezing: does it still work after the sensor freezes and thaws? This matters in Colorado.
- Supplemental capabilities required by the specification.
Many rebates require the WaterSense label, so check EPA's product finder for your exact model.
Soil sensor vs. weather-based controller
| Weather-based controller | Soil moisture sensor | |
|---|---|---|
| What it uses | Local weather data and forecasts to estimate plant water needs | A direct reading of moisture in the root zone |
| Strengths | Adjusts all zones; no buried hardware | Responds to actual conditions, including rain, irrigation, and soil type |
| Limitations | Estimates may not match your microclimate | Reading represents the spot where the probe sits; placement matters |
| Typical setup | Replaces your controller | Stand-alone controller or add-on to your existing one |
They aren't mutually exclusive. Aurora's rebate rules, for instance, require that a rebated soil moisture sensor connect to the irrigation controller and adjust watering schedules (City of Aurora). Many homeowners pair one with a smart controller.
Placement and setup tips
- Choose a representative zone. Put the probe in a typical sunny lawn area, not a low spot that collects water or a shady corner.
- Bury it in the root zone, following the manufacturer's depth guidance for turf.
- Keep it away from the edges of spray patterns, sidewalks, and downspouts.
- Start with the manufacturer's threshold, then adjust if the lawn looks drought-stressed or stays soggy.
- Check compatibility first. Confirm your controller has a sensor input that supports soil moisture sensors, or choose a sensor designed as an add-on.
- Remember winterization. Follow the maker's instructions for freeze periods, and check the sensor reads normally when you start the system in spring.
Colorado rebates for soil moisture sensors (2026)
| Provider | Rebate | Notes |
|---|---|---|
| Aurora Water | $100 each, up to two per residence | Must connect to the irrigation controller and adjust schedules (Aurora) |
| Fort Collins Utilities | Up to $60 | Apply within 60 days of purchase (Fort Collins) |
Check your own provider's current list. Programs and amounts change each year. Our Front Range rebate table covers controllers and rain sensors too.
Rain sensors: the simpler cousin
A rain sensor shuts off watering during or after rain but doesn't measure soil moisture. It's cheaper and widely rebated. Colorado Springs Utilities pays $25 for a wired sensor and $50 for a wireless sensor, and notes that smart-controller rain-delay features don't qualify for its rebate (CSU). A rain sensor won't tell you whether the root zone is dry after a hot, windy week. A soil sensor will.
Common questions
Does a soil moisture sensor let me water more often?
No. A sensor can only skip or allow watering that's already scheduled. Your utility's rules still apply. In Colorado Springs, that means up to three watering days a week and, from May 1 to Oct. 15, watering only before 10 a.m. or after 6 p.m. (CSU Water Wise Rules). Program your allowed days first, then let the sensor decide whether each scheduled run is needed.
Will it survive a Colorado winter?
Freeze tolerance is part of WaterSense testing. EPA evaluates whether a labeled sensor still functions after its sensor mechanism is frozen and thawed (EPA). Choosing a labeled model is the easiest way to get that assurance. Follow the manufacturer's winterization steps along with your sprinkler blowout.
Can I stack rebates for a controller and a sensor?
Some utilities list them separately. Aurora, for example, lists a smart controller rebate (up to $200) and a soil moisture sensor rebate ($100 each, up to two) as separate line items, each with its own requirements (City of Aurora). Read each program's rules, and keep separate receipts and installation photos.
Do I need one if I already have a weather-based controller?
Not necessarily. A weather-based controller already adjusts for weather. A sensor adds a direct check of what's happening in the soil, which can help where your yard's conditions differ from the weather data, such as sandy or clay soils, slopes, or heavy shade. If you aren't sure, start with the controller and add a sensor later if the schedule seems off.
Thinking bigger? Farm-scale sensing
On farms, soil moisture monitoring is a core irrigation-management tool. Colorado State University has field-tested sensors from several manufacturers in irrigated corn across three river basins (CSU Agricultural Experiment Station). See our farm soil moisture and VRI guide.
Sources
- U.S. EPA WaterSense, Soil Moisture-Based Irrigation Controllers: https://www.epa.gov/watersense/soil-moisture-based-irrigation-controllers
- City of Aurora, Irrigation Rebates: https://www.auroragov.org/residents/water/rebates/irrigation/irrigation_rebates
- City of Fort Collins, Residential Water Conservation: https://www.fortcollins.gov/Services/Utilities/Programs-and-Rebates/Water-Programs/Residential-Water-Conservation
- Colorado Springs Utilities, Rain Sensor rebate: https://www.csu.org/rebates-programs/rain-sensor
- Colorado State University AES, Irrigated soil moisture sensors: https://aes.colostate.edu/wcrc/grand-valley/irrigation-and-water-resources/irrigated-soil-moisture-sensors/