As I ran the irrigation system for the first few times, I had no idea how much money it was costing me. We’re only billed every two months so it would take a while to find out and I didn’t want a big surprise. To get a rough idea, I ran each zone for a few minutes and then took a reading from the water meter. Thankfully we have very accurate water meters so I was able to get good readings.
Coupled with that effort, I also put some jars around the yard as the irrigation ran to see how much water it was putting down. The books and web sites I’ve read say that you should give your yard 1” of rain per week spread over either one or two sessions. This encourages the grass to build up a better root system than they would if you watered a little bit every day. Each zone in my system needs to be on for 30 minutes to give the grass 1” of water.
Putting all that info into a spreadsheet tells me that it costs about $4/week to water my lawn. That will probably be closer to $10 once we get the front yard done. For a huge portion of the year, it’s either cool or wet enough that I won’t need to water, but during those few hot dry weeks we get in July and August every year, it will be awesome to have a healthy green lawn.