I have a 500 VA UPS and it's more than sufficient for me to shut down my computer if there's a power failure. I have an overclocked A64 with overclocked RAM and an overclocked 6800GT and two hard drives, 2 optical drives, a 17 inch monitor... if you're on page 2 of a 10 page document you're writing and want to finish it if the power goes out, you're going to need more power. But even a 500 VA UPS gives me AT least 5 minutes to shut down, and that's more than enough.