The footprint of our house that puts water into gutters is about 2,500 square feet. This means one inch of water will put about 1,500 gallons through our gutters. with 44 inches of rainfall per year, that means we could collect 66,000 gallons of water from the roof. Water costs $5 per 1,000 gallons, so if we could use every gallon of water that falls on the roof, it would save us $330 per year.
It looks like you can get a 2,000 gallon water tank for about $2,000. If we need enough capacity to capture 4 inches of water, that would require 6,000 gallon capacity. I did find a 6,000 gallon tank for about $3,500. We’d also need a pump, additional piping, and the cost of installing it. The best scenario I can imagine would put the cost at $4,000.
If we were able to use all 66,000 gallons instead of rural water, it would take us 12 years to break even if it were to cost $4,000. Chances seem fairly high that there would be other expenses–like repairs along the way which would push the cost up even more.
Realistically, unless the price of water shoots up dramatically, it is going to be less expensive to water our grass using rural water than collected rain water.
