UV is a good way to treat water and as light as any filter. The largest weight penalty is the spare batteries needed on longer trips, since they only last about two or three weeks. With a LED producing UV-C, longevity can be greatly increased. I would guess a minimum of 3 times. The LED produces the same band of disinfecting UV light and at a 12% efficiency! Yup, you read that TWELVE PERCENT! And, they are typical doped electronics. Not the power guzzling mercury bulbs currently available with the largish starting draws.
