You have access to the utility grid and your primary goal is to have backup power when there is an outage. Off-grid: You do not have access to the utility grid. Your primary goal is to live where it is not accessible. Once you identify your goals, you can make a final decision based on price.Guarantee = 5 years solar suppliers: Xufeng Solar Co., LtdSmall Solar Panel in stock website:http://www.nbnewsolar.com/small-solar-panels/