Yes and no. Reverse osmosis filters use water to clean water, and therefore need to fill its tank in order to be able to push the water across the semipermeable membrane and filter out the impurities. It’s the same as an extra three toilet flushes per month in terms of water usage and therefore you won’t see any changes on your water bill. If you’re wanting to clamp down on water usage, the whole home water filter may be more geared towards your needs.