This little bottle allows me to make 27 gallons (in the same 1 gallon container). So far this is working well - winter might make it interesting as I need to find alcohol to keep it warm - but for summer it's a great quality. Windshield washer fluid at any auto parts store or discount store is $3-4 per gallon. 27 gallons for what two would cost me at retail — and that's 27 plastic pitchers that don't need to be recycled or thrown in a landfill. I use filtered water to avoid any mineral deposits etc.