I bought one of these (or very similar) beginning of last summer after we bought our new patio furniture, including a huge umbrella. The cord on the solar panel is just long enough to reach the edge of our oversized umbrella, so a standard table-cover umbrella leaves plenty of slack. It works like a champ, on at dusk and all. The 500mAh battery is inadequate to last all night, even on a really good charge, but it seems to typically blink off around 2-3 am, time to go in anyway. 
It’s not really bright, but if it’s the only light around, it’ll at least keep you from knocking over your beverage, but you’re not going to be reading by it. It’s more just for the accent of light than visibility. I’m thinking I’ll get another one and overlay them so we’ll have double the lights on the arms of the umbrella, or just a spare in the event the first one finally dies, as these things tend to do after 2-3 years out in the elements.
OR you could have just spent the $18+$5 & $18+$5 on 1 real good light found on Amazon.com instead of mounting 2 solar panels and Christmas wiring all over your umbrella