Quick answer
A smart irrigation controller is a sprinkler timer that changes how long, or whether, your system runs by reading weather data or soil moisture instead of repeating one fixed clock schedule.
EPA WaterSense labels two kinds: weather-based controllers and soil moisture-based controllers. A labeled model must pass independent tests. It still needs correct setup, because it cannot fix a badly designed or poorly kept system.
Quick facts
The key facts about Smart Irrigation Controller, with sources:
- Two labeled types
- Weather-based (uses local weather) and soil moisture-based (uses a probe in the ground) 1
- Current weather-based spec
- Version 1.1, released September 2021; it replaced Version 1.0 from 2011 34
- Pass mark, adequacy
- At least 80 percent for every zone in a 30-day test 4
- Pass mark, excess
- No more than 10 percent per zone and an average of 5 percent or less 4
- EPA savings claim
- Up to 15,000 gallons per year for an average home that replaces a clock-based timer 1
- What it cannot do
- Correct a poorly designed or poorly maintained irrigation system 6
Key takeaways
- A smart controller replaces a fixed clock schedule with feedback from weather or soil moisture.
- The WaterSense label is a pass mark from an independent test, not a promise about your yard.
- Weather-based models estimate water loss. Soil moisture models measure water in the ground. Some do both.
- Savings depend on setup. Wrong sprinkler, soil or slope settings can cancel the benefit.
- A labeled controller still follows local watering rules, because the spec requires it to support them.
A sprinkler timer that listens: the plain-English definition
A standard sprinkler timer is a clock. You pick days and start times, and it runs the zones whether the lawn is thirsty or not. A smart controller adds a source of feedback. It reads something about the weather or the soil, then shortens, skips or lengthens the run.
The Irrigation Association, quoted by the University of Florida, defines smart controllers as controllers that reduce outdoor water use by monitoring and using information about site conditions 5. EPA WaterSense uses a narrower, testable version.
It labels controllers that “use local weather and landscape conditions to tailor watering schedules,” or that monitor soil moisture “to prevent irrigation when water is not needed” 2.
The reason this matters is waste. EPA says residential outdoor use is nearly 8 billion gallons per day, mostly for landscape irrigation, and experts estimate that as much as 50 percent of it is wasted through overwatering 1. A clock cannot see rain, cool weather or wet soil.
This page owns the definition and the test. For the basic timer itself, see irrigation controllers. For the add-on devices that feed a controller, see soil moisture sensors and rain sensors.
How a weather-based controller decides what to do
A weather-based controller, also called an ET controller, tries to put back the water the landscape lost since the last run.
ET stands for evapotranspiration, which is water lost by evaporation from soil plus water released by plants.
UF/IFAS describes the goal as replacing all or part of the water lost through ET since the last irrigation 5.
- It gets weather data. The data comes from a signal sent to the controller, from a preloaded regional water-use curve, or from sensors on site 5.
- It estimates water loss. It combines that data with what you entered about the plants, soil, slope, shade and sprinklers 6.
- It converts loss into run time. The sprinkler application rate, in inches per hour, tells it how long each zone must run to put back that depth 6.
- It adjusts or skips. A cool, humid or rainy stretch shortens or cancels runs. A hot, windy stretch lengthens them.
- It tells you when it is blind. A WaterSense labeled model must show the user when it is not getting a signal or sensor input and is not adjusting to current weather 4.
- Weather data inSignal, regional curve or on-site sensor
- Site settingsPlants, soil, slope, shade, sprinkler type
- Water-loss estimateET since the last run
- Run time outMinutes per zone, or a skipped run
- FallbackHistorical data or percent adjust if the signal is lost
Flow follows UF/IFAS EDIS AE442 and AE445 and WaterSense spec Version 1.1, sections 4.3 and 4.7. Source: [5] [6] [4]
Weather-based, soil moisture-based and combined controllers
| Type | What it reads | How it acts | Notes from the sources |
|---|---|---|---|
| Weather-based (ET) controller | Local weather and landscape conditions | Sets or changes run times to match estimated water loss 2 | Three data routes: signal-based, historical ET, on-site weather measurement 5 |
| Soil moisture-based controller | Water content in the soil near a probe | Allows or blocks a scheduled run, or starts and stops runs at set thresholds 7 | Most residential units are the bypass type, an add-on wired to a conventional timer 5 |
| Combined controller | Both weather and soil data | Uses both inputs at once | Must be certified under both specifications to carry the label 1 |
| Clock-based timer (not smart) | Nothing but the clock | Runs the program you set | EPA compares labeled models against this baseline 1 |
A rain sensor alone does not make a controller smart
The WaterSense weather-based spec says rainfall devices and soil moisture sensors do not modify ET. They interrupt or modify an existing schedule, so used alone they do not meet its on-site weather sensor requirement 4. A controller must still be able to connect to one 4.
Example: reading the WaterSense pass marks on a six-zone test
The thresholds below are from WaterSense Specification Version 1.1, section 3.1 4. The zone scores are invented to show how the rule works. They are not from any real product.
| Zone (example) | Adequacy score | Excess score | Result against the rule |
|---|---|---|---|
| Zone 1 | 91 percent | 3 percent | Passes: adequacy at least 80, excess at most 10 |
| Zone 2 | 84 percent | 6 percent | Passes |
| Zone 3 | 88 percent | 4 percent | Passes |
| Zone 4 | 80 percent | 9 percent | Passes, with no room to spare on either score |
| Zone 5 | 93 percent | 2 percent | Passes |
| Zone 6 | 86 percent | 7 percent | Passes on its own, but see the average below |
What the scores mean
Adequacy shows the controller’s ability to meet plant water needs. Excess shows its ability to avoid overwatering 3. Both are lab-style test results, not a forecast for your lawn.
Check the math. The six excess scores sum to 31, and 31 divided by 6 is about 5.2. Each zone passes alone, yet the average is above the limit of 5 percent 4.
That shows why the label needs both a per-zone rule and an average rule. The test lasts 30 consecutive days, and can run longer until a 30-day stretch meets the weather requirements of the ASABE method 4.
Where you meet the term: boxes, bids and rebate forms
On a product box or listing. Look for the WaterSense mark and the words weather-based or soil moisture. EPA publishes a product search for labeled controllers on its WaterSense site 2.
On an irrigation bid. A contractor may offer a “smart” upgrade at the controller.
Ask whether it is a labeled model, which type it is, what weather source it uses and who sets the soil, slope and sprinkler inputs.
Our landscaping estimates guide shows how to compare scope lines, and irrigation services explains the work in a full system.
On a utility or turf rebate form. EPA notes that some utilities offer rebates for labeled controllers 1. Programs and rules vary, so check the turf rebate research and the turf rebate tool.
In commercial sites. EPA also presents these controllers for schools, hotels and office buildings, so many models are built for many zones 1.
What smart controllers can do, and where they fall short
What the evidence supports
- EPA says labeled controllers can significantly reduce overwatering by applying water only when plants need it, and estimates up to 15,000 gallons saved per year for an average home that replaces a clock-based timer 1.
- UF reported a 21 to 31 percent reduction in water use for properly installed and programmed ET controllers in residential landscapes 5.
- A labeled weather-based model must support watering restrictions, a percent adjust feature and a rain or soil moisture input 4.
- A soil moisture model reacts to the actual ground, not an estimate 7.
What the evidence does not promise
- Savings vary by brand tested, weather and site. UF field plots ranged from 14 percent more water applied to a 68 percent reduction for ET controllers 5.
- A smart controller cannot correct a poorly designed or poorly maintained irrigation system 6.
- The label tests a controller, not your install. Wrong inputs give wrong run times 6.
- Some models rely on a signal. If it drops, the controller falls back to a simpler method 4.
Limits and open points in the evidence
The savings numbers come from field plots and a few residential studies, mostly in Florida. UF says results vary by brand, weather and site 5. EPA’s 15,000-gallon figure is an average for one home. The page does not show how it was calculated, so treat it as an estimate.
The WaterSense weather-based spec tests a controller in a defined 30-day period with reference weather data. It is a performance screen and says conformance indicates the controller has the capacity to produce appropriate schedules when programmed in line with the maker’s instructions 4.
We did not find a published lifespan for these controllers in the sources we read, so we give none. We also found no independent source that ranks brands, and this page does not.
Soil moisture sensors have their own limits. UF notes that setpoints vary by brand and the timer still has to be programmed correctly 7. The soil moisture sensor page covers placement.
What changes the price, and what the sources say about lifespan
We do not publish prices. A bid or shelf price moves with a few things the sources name. One is the form: a stand-alone controller, an add-on device or a plug-in device are all covered by the spec 4.
Another is the number of zones and whether you need separate programs for zones with different water needs. The third is the weather source: a signal, a preloaded regional curve or an on-site weather station 5.
Installation matters as much as the box. UF stresses that correct programming for each unique landscape is critical to cutting water use 6. A contractor who measures sprinkler application rates with catch cans is doing more work than one who accepts defaults. Ask which.
Savings are the other side of the ledger. They depend on your water rates, your lawn and your old habits, so we give no payback figure. Use the lawn water cost calculator to size your current use, and the cost hub for what sets a bid.
No source we read gives a service life for the controller. Ask the maker for the warranty terms, and see our guide to choosing a landscaping company for questions to put in writing.
Who sets it up, and the inputs a weather-based unit needs
A homeowner or an irrigation contractor can install a controller. The part that decides the result is the setup. UF/IFAS lists the inputs an ET controller needs, roughly in the order a user enters them 6.
- Choose the sprinkler type for each zone: spray head, rotor, impact, bubbler or drip emitter.
- Enter the application rate in inches per hour, from the maker’s data or a catch-can test.
- Enter an efficiency or uniformity value. UF warns that a lower efficiency number makes the controller apply more water 6.
- Pick the soil type and the plant type. On compacted construction fill, UF advises choosing the soil one level lower 6.
- Enter slope and shade. Steeper slopes call for cycle-and-soak timing 6.
- Connect a rain sensor if the controller has a sensor port, and enter the zip code 6.
Mark buried lines and call 811 before any digging
Moving a valve, adding a sensor probe in the lawn or changing a zone means digging near buried irrigation pipe, wire and possibly utilities. Call 811 first. Mains power work belongs to a licensed electrician; low-voltage timer wiring still follows the maker’s manual.
Keeping a smart controller honest
Upkeep tasks are listed here without fixed dates. Local weather and the maker’s manual set the timing.
- Supervise it. UF says ET controllers still require regular supervision or maintenance 6.
- Re-check settings after changes. New plants, a new bed, a swapped nozzle or a fresh zip code all change the inputs 6.
- Watch for a lost signal. Signal-based models need the signal to stay on. The spec requires a labeled unit to tell you when it is not receiving one 4.
- Test the whole system. Run each zone by hand and look for broken heads, leaks and spray hitting pavement. A controller reads the numbers you give it, not the damage it cannot see.
- Keep soil sensors clear of traffic. UF says not to bury a sensor in a traffic area, so the soil around it does not compact 7.
Warning signs the controller is not helping
- Run times that never change. If the program looks the same in a cool wet week and a hot dry one, the weather feed or the sensor may be off.
- Soggy ground after a run. The efficiency, soil or slope input may be wrong, or the application rate is higher than entered.
- Dry spots in one zone. Look at the sprinkler heads first. A controller cannot fix a clogged nozzle.
- A “no signal” message. The unit may be running on a fallback, such as historical weather data or a percent adjust setting 4.
- A rain sensor that is not connected. UF lists an unconnected rain sensor among common mistakes 6.
If these continue after you check the settings, ask a licensed irrigation contractor to audit the system. Check landscaping licensing by state for who holds which license where you live.
Standards and rules behind the label
A voluntary EPA label. WaterSense is an EPA program. A product earns the label by being independently certified to a published specification 1. It is not a law or a code.
The specification. The weather-based spec is Version 1.1, dated September 2, 2021. It replaces Version 1.0, released November 3, 2011, and EPA calls the revisions minor 34. Its test method was adopted into ANSI/ASABE S627, Weather-Based Landscape Irrigation Control Systems 3.
What it requires beyond the test. Section 4 requires, among other things, the ability to keep programmed settings through a power loss without a battery, to store at least three programs or program zones separately, and to connect to a rain or soil moisture device 4.
It also requires support for watering restrictions, which we cover in the local section.
Local rules still apply. Watering days, times and bans are set by your water supplier or city. The tracker in the local section lists what we have verified.
Smart controller vs. the devices it is confused with
| Device | What it reads | What it changes | Where to read more |
|---|---|---|---|
| Smart irrigation controller | Weather and or soil moisture | Run times and skipped runs across the schedule 2 | This page |
| Basic irrigation controller | The clock | Nothing; runs the set program | Irrigation controller page |
| Rain sensor | Rainfall at a point | Interrupts a scheduled run after a set amount 8 | Rain sensor page |
| Soil moisture sensor | Soil water content | Bypasses or starts runs at a threshold 7 | Soil moisture sensor page |
| Pressure-regulating sprinkler body | Line pressure | Holds nozzle pressure steady; not a scheduler 9 | Irrigation water pressure |
Common smart controller myths
- Myth A smart controller sets itself up.
- Reality UF says correct programming for each unique landscape is critical, and that controllers cannot correct a poorly designed or poorly maintained system 6.
- Myth Every smart controller has the WaterSense label.
- Reality The label requires independent certification to a specification. Many products use the word smart without it 1.
- Myth A rain sensor makes a controller smart.
- Reality The spec says rainfall devices and soil moisture sensors alone do not meet its on-site weather sensor requirement 4.
- Myth It will always save the same amount.
- Reality UF says savings depend on brand, weather and site, and found results from 14 percent more water to a 68 percent cut 5.
- Myth It lets you ignore local watering rules.
- Reality The spec requires a labeled controller to be able to follow restrictions. Whether yours does is up to you and your water supplier 4.
The regional variable: watering restrictions and climate
Two regional facts shape how a smart controller works for you. First, climate sets the water-loss estimate. The unit needs your location, and UF notes the zip code should be updated for where the controller sits 6.
Second, watering rules differ by supplier. WaterSense spec section 4.5 requires labeled controllers to support set days of the week, even or odd day scheduling or intervals of two to seven days, runtimes that avoid a prohibited time of day, and a full shutoff for outdoor watering bans 4.
So the hardware can follow your rules. Check your own rules in the tracker, because we do not publish a national schedule.
When a smart controller is worth it, and your next step
A smart controller is worth a look if your system is sound, your lawn or beds are sized to the zones, and your current program waters on a fixed clock. It adds less if heads leak, nozzles are mismatched or zones mix different plant types, because those faults live below the controller.
Your next step is to run every zone and fix what you see. Then decide between weather-based and soil moisture-based. A soil moisture add-on suits a simple timer and one representative spot. A weather-based unit suits many zones with different exposures. Then check your supplier for rebates.
If you hire it out, ask for the model type, weather source and the inputs the installer will enter. Our sprinkler runtime calculator helps you sanity-check the run times that come out.
Questions about Smart Irrigation Controller
What is a smart irrigation controller?
A smart irrigation controller is a sprinkler timer that adjusts or skips runs using weather data or soil moisture instead of one fixed clock schedule. EPA WaterSense labels two types: weather-based and soil moisture-based. The label means an independent body tested the model. It does not guarantee savings in your yard.
How does a smart sprinkler controller work?
A weather-based unit estimates the water your landscape lost since the last run, using weather data and the plant, soil, slope and sprinkler settings you enter. It then sets run times to put that water back. A soil moisture unit reads a probe and allows or blocks scheduled runs.
What does the WaterSense label mean on an irrigation controller?
It means the controller was independently certified to an EPA specification. For weather-based models, the test needs an irrigation adequacy score of at least 80 percent in every zone, excess of at most 10 percent per zone, and an average excess of 5 percent or less across six zones, over a 30-day test.
How much water can a smart controller save?
It depends on your site. EPA says a labeled controller can save an average home up to 15,000 gallons per year compared with a clock timer. UF field work shows a wide range, from 14 percent more water to a 68 percent cut in plots, and 21 to 31 percent in residential landscapes.
What is the difference between weather-based and soil moisture-based controllers?
Weather-based controllers estimate water loss from weather and site settings. Soil moisture-based controllers measure water in the ground and skip runs when the soil is wet enough. EPA says a controller that uses both must be certified under both specifications to carry the label.
Do smart controllers still need a rain sensor?
Many do. The WaterSense weather-based spec requires a controller to connect to a rainfall device or soil moisture sensor. UF/IFAS also advises connecting a rain sensor to the controller’s sensor port when one is available, as it lists an unconnected sensor among common mistakes.
Will a smart controller work with watering restrictions?
A labeled weather-based model must be able to. The spec requires set days of the week, even or odd days, intervals of two to seven days, runtimes that avoid a banned time of day, and a full shutoff. Your supplier’s actual rules still decide what you may run, so check them locally.
Can a smart controller fix a bad sprinkler system?
No. UF/IFAS states that these controllers cannot correct a poorly designed or poorly maintained irrigation system. Broken heads, wrong nozzles and mixed zones keep wasting water. Fix those first, then set the controller with measured application rates.
What happens when the weather signal is lost?
A labeled weather-based controller must tell the user it is not receiving a signal or sensor input, and it must fall back to a proxy for historical weather data or a percent adjust feature. It keeps running, but no longer reacts to current weather.
Are there rebates for smart irrigation controllers?
Some utilities offer them, according to EPA. Terms differ by supplier and change over time. Check your water provider and our turf rebate research page before you buy, because some programs require a labeled model or a set installer.
Sources
- U.S. EPA WaterSense, WaterSense Labeled Controllers, retrieved .
- U.S. EPA WaterSense, Irrigation Controllers, retrieved .
- U.S. EPA WaterSense, Weather-Based Irrigation Controllers, retrieved .
- U.S. EPA WaterSense, Specification for Weather-Based Irrigation Controllers, Version 1.1 (September 2, 2021), PDF read as text, retrieved .
- UF/IFAS Extension, Smart Irrigation Controllers: What Makes an Irrigation Controller Smart? (EDIS AE442), retrieved .
- UF/IFAS Extension, Smart Irrigation Controllers: Programming Guidelines for Evapotranspiration-Based Irrigation Controllers (EDIS AE445), retrieved .
- UF/IFAS Extension, Smart Irrigation Controllers: How Do Soil Moisture Sensor (SMS) Systems Work? (EDIS AE437), retrieved .
- UF/IFAS Extension, Residential Irrigation System Rainfall Shutoff Devices, or Rain Sensors (EDIS ABE325/AE221), retrieved .
- U.S. EPA WaterSense, Spray Sprinkler Bodies, retrieved .
Expert review
Written by the HyreYard Research Desk. Not yet reviewed by an outside expert. We say so rather than imply a review that has not happened; see our editorial policy.
How the numbers were checked: The label definition, savings claim and type split come from EPA WaterSense pages. The pass marks and required features come from the Version 1.1 specification PDF, read as text with pdftotext.
Field savings and setup inputs come from UF/IFAS EDIS AE442, AE445 and AE437, which show no publication date. The example zone scores are invented and labeled. No prices, brands or schedules are given.
Suggest a correction. We fix errors and say what changed.