I don't have any Windows machines that would be always on. That's why I have a NAS.
If you only have 250G of stuff to backup, I think I'd sync it to the computer you have online and then back that up to something free like Google Drive. You could get it to the cloud for free if you did that.
I've been waiting for prices on cloud storage to come down... I'm connected via fiber and seem to be getting about 50mbps upstream even though the ISP promised 100/10. It would be painful to do the first sync, but since I'm mainly interested in having offsite backups for photos (250GB) it should be doable.
But up to now the prices have been way too high so I've just kept one disk at work. Maybe I should just code a plugin for one of the cheaper backup options myself.
Welcome To SNBForums
SNBForums is a community for anyone who wants to learn about or discuss the latest in wireless routers, network storage and the ins and outs of building and maintaining a small network.
If you'd like to post a question, simply register and have at it!
While you're at it, please check out SmallNetBuilder for product reviews and our famous Router Charts, Ranker and plenty more!