How to Budget Annual Filter Costs

Hardware is a one-time cost you will amortize over five to ten years. Cartridges are a subscription you cannot cancel if you want the certification claim to keep being true.

Total annual cost = (cartridge price ÷ rated gallons) × gallons you actually filter per year, multiplied for each stage the system requires.

Pitcher or dispenser: typically $40–$120 per year, driven almost entirely by how much you drink. Cartridges average around 40 gallons each.

Faucet-mount: roughly $60–$150 per year, with cartridges rated for 100–200 gallons depending on the model.

Under-sink carbon: about $60–$150 per year, often a single annual cartridge plus a pre-filter.

Under-sink RO: commonly $120–$300 per year, because there are three or four stages — sediment, carbon, membrane, post-carbon — each on its own schedule.

Whole-house: $150–$500 per year, and higher where sediment loads are heavy or the system includes a softener's salt and resin costs.

Count drinking and cooking water only. A common planning figure is about half a gallon per person per day for drinking, plus another half gallon for cooking and coffee in households that cook at home.

A family of four: roughly 4–6 gallons per day, or 1,500–2,200 gallons per year. That single number turns every spec sheet into a comparable cost.

If you also fill humidifiers, pets, or a coffee urn, add those — they are real filtered volume.

Buying whole-house treatment for a drinking-water-only concern. Treating laundry and garden water for lead is expensive and pointless.

Replacing an entire RO manifold because one stage is exhausted. Work out which cartridge is due and buy that one.

Ignoring multipacks and subscription pricing, which often cut cartridge cost by 20–30%.

Replacing early by taste. Taste is a useful signal for carbon but a poor one for membranes; use the rated volume or a TDS reading for those.

Write the cartridge model numbers in the manual and tape the purchase date inside the cabinet door. The most common cause of expired filtration is not price — it is forgetting.

Set the replacement interval as a calendar reminder, and re-check it once a year against your actual consumption.

Keep a spare of the fastest-wearing stage. It is cheaper than a week of unfiltered water while you wait for delivery.