What an RO purifier costs to run per year, with the working shown.

The five lines on the bill

A domestic RO purifier costs money in five ways after you buy it: the pre-filter cartridges, the membrane, the UV lamp, the electricity it draws, and the water it sends to drain. Some are on a schedule and some are not. Two of them are small enough that people overestimate them, and one is large enough that people forget it. Each line below gives the figure, where it came from, and how to redo it with your own numbers.

The intervals used throughout are the ones on the filter change schedule: sediment every 6 to 8 months on borewell water and up to 12 on municipal, carbon up to 12 months, membrane 18 to 24 months, pump when it fails.

Line 1: sediment and carbon

The sediment cartridge is ₹190 in both fits, Branded-Fit and Universal-Fit. The carbon cartridge is ₹220 in Universal-Fit and ₹250 in Branded-Fit. On municipal supply, one of each a year: ₹410 to ₹440. On borewell water the sediment goes at 6 to 8 months, so budget one and a half to two a year: ₹505 to ₹630.

If your purifier has a separate wall-mounted pre-filter bowl ahead of it, add its candle: the 9-inch yarn-wound candle is ₹150 and a pair of 10-inch spun candles ₹259. Change it when it browns, which on borewell water can be every few months.

Line 2: the membrane

The membrane is the largest single part and the only one whose interval you should measure rather than assume. LUXGEN lists three: the 80 GPD at ₹650, the 100 GPD at ₹800, and the 100 GPD molded high-TDS membrane at ₹900. Spread over its life, the yearly cost is the price divided by the years it lasts. An 80 GPD lasting two years is ₹325 a year; a molded membrane lasting eighteen months is ₹600 a year. So ₹325 to ₹600, and the membrane replacement guide explains how to tell which end you are at. Which of the three you need depends on your feed TDS and your pump, and the 80 vs 100 GPD guide settles that.

Line 3: the UV lamp

Every LUXGEN purifier has a UV stage, and the lamp in a domestic purifier is replaced roughly yearly. LUXGEN does not list a lamp on this site at present, so this line is a market figure: lamps for domestic purifiers typically cost a few hundred rupees, and the price varies by make and fitting. Put in the figure for your machine. If the lamp is on a comprehensive service plan, the AMC guide covers how to value that.

Line 4: electricity

Smaller than most people expect. The LUXGEN booster pump is rated 24 V DC at about 1.10 A, which is roughly 26 W while it runs. Add a UV lamp of a handful of watts and the losses in the power adapter, and a purifier draws in the region of 30 to 40 W while it is making water, and next to nothing while idle. The formula: watts × hours per day × 365 ÷ 1000 = units per year, then × your tariff.

Worked: 40 W for one hour a day is 14.6 units a year. At ₹8 a unit that is about ₹117 a year. A purifier making 10 litres a day at the pump's 1.5 litres per minute runs well under an hour, so this is an upper figure for a typical household. Take the wattage from your own purifier's label and the tariff from your bill.

Line 5: reject water

The one people forget, and on some supplies the one that matters. A domestic RO sends two to three litres to drain for every litre it purifies. A household using 10 litres of purified water a day therefore sends 20 to 30 litres a day to drain: 7,300 to 11,000 litres a year, or 7 to 11 kilolitres.

What that costs depends entirely on how you buy water. On a metered municipal supply, multiply by your rate per kilolitre: at ₹10 a kilolitre it is ₹73 to ₹110 a year; at ₹50 it is ₹365 to ₹550. On tanker water it is the tanker price per litre times the reject litres, and that is usually the largest line on this whole page. Collecting the reject for mopping and for salt-tolerant plants turns it from a cost into a bucket.

The yearly total, and how to redo it

Adding the lines that are on this site: parts come to roughly ₹735 to ₹890 a year on municipal supply and ₹940 to ₹1,230 on borewell, before the lamp, the power and the water. With a UV lamp at a few hundred rupees, electricity near ₹100 and water at a municipal rate, a household lands somewhere in the region of ₹1,100 to ₹2,300 a year, plus ₹1,299 whenever the pump fails. Over five years that is comparable to or more than the purifier cost, which is the point of the page.

To redo it: take your intervals from the schedule, your prices from the linked product pages, your wattage from the label, and your water rate from the bill. The reading that decides the membrane line is the output TDS against the feed, and the RO output TDS guide shows how to take it.