Run Your Numbers
Slide in your roof size and local rainfall. We’ll show your annual collection potential, how many barrels a typical storm fills, and what that water is worth.
Use your home’s footprint, not total floor area, a two-story 2,400 sq ft home has roughly a 1,200 sq ft roof.
US average is about 38". Phoenix ~8", Denver ~15", Chicago ~38", Seattle ~39", Atlanta ~50", New Orleans ~62".
Real systems lose some water to splash, overflow, and first-flush diversion. 80 to 90% is typical for a well-installed setup.
Gallons = roof area (sq ft) × rainfall (inches) × 0.623 × efficiency. The 0.623 constant is the gallons in one inch of water over one square foot, the same figure USGS and university extension programs use.
What The Number Means
One 50-gallon barrel with a diverter covers container plants and a small bed. Start simple, you can always add a second barrel.
Rain Wizard 50 + DiverterA 65-gallon barrel, or two 50s on separate downspouts, keeps a full vegetable garden watered between storms.
Rain Wizard 65Your roof outproduces barrels. Multiple linked barrels now, with a cistern and staged filtration as the long-term upgrade path.
Read the filtration guideA Worked Example
Take a typical 1,200 sq ft roof in a city with 38 inches of annual rain. At 85% efficiency, that’s about 24,000 gallons a year, enough to fill a backyard swimming pool.
Even catching a fraction of it in one barrel changes your summer: the EPA puts a single barrel’s savings at about 1,300 gallons over the season, right when watering restrictions hit hardest.
Every model we carry lists capacity, ideal roof size, install difficulty, and honest pros and cons.