I bought the 20,000 version a few months ago. Was surprised at its heaviness and largish size, but it was ok for what I wanted. I use it to power a little USB fan at the desk where I volunteer 5 hours a week. It will run the fan for over 30 hours before needing a recharge. That's a month and half with no recharge, using it 5 hours a week, all at once. Impressive performance! It takes a good long while to charge--I leave it the charging cord overnight every 6 weeks. I'm buying another one for a similar use elsewhere.