It’s estimated that one-third of residential water use is directed to front and back yards, illustrating how watering a lawn can be expensive to both homeowners and to the environment.

Reducing these costs can be simple, however. All it takes is a working a rain-monitoring device. Rain monitors are basic hardware that typically install between a lawn’s sprinkler heads and its water source.

Using a built-in reservoir, the devices collect and measure natural rainfall, using the levels to determine whether the sprinkler system should be engaged on a given day. With one particular, low-tech model, if the reservoir is holding a half-inch of water or more, the monitor “locks” the sprinkler heads from firing.

If you’ve ever watched your lawn get watered through a rainstorm, you can understand the value of a device like this.

Rain-monitoring devices range in cost from $12 to several hundred dollars with the low-tech model referenced above closer to $12. Wireless transmitting devices are at the upper-end of the range.

Many lawn care experts recommend 1 inch of water per week.