Purchase, filters, membrane, waste water, electricity: what a litre of reverse osmosis water really costs, compared with bottled water and tap water, and for whom the system pays off.
In short
- A litre of reverse osmosis water costs 5 to 15 cents depending on system and use, including depreciation.
- Bottled water costs 20 to 80 cents per litre, tap water 0.2 to 0.5 cents.
- From about 3 litres a day, the system is cheaper than discount-supermarket water after two to three years.
- The real reason is rarely the price, but pollutants, limescale or taste.
The cost components
- Purchase: Basic tank systems from 200 euros, good direct-flow systems 500 to 1,200 euros, countertop units 300 to 600 euros. Installation by a plumber 100 to 250 euros if you do not do it yourself.
- Pre-filters: Sediment and activated carbon every six months, together 30 to 60 euros a year.
- Membrane: Every two to three years, 40 to 120 euros.
- Post-filter and remineralisation: 20 to 50 euros a year.
- Waste water: At 1:1 and 10 litres a day, around 3.6 cubic metres a year, about 15 to 20 euros. At 1:3, three times that.
- Electricity: Pump and, if fitted, UV, under 10 euros a year.
What a litre costs
| Water | Cost per litre | Per year at 10 litres a day |
|---|---|---|
| Tap water | 0.2 to 0.5 cents | around 15 euros |
| Reverse osmosis water, good system, calculated over 5 years | 5 to 8 cents | around 250 euros |
| Reverse osmosis water, basic tank system | 8 to 15 cents | around 400 euros |
| Soda maker with tap water | 10 to 15 cents | around 450 euros |
| Discount-supermarket bottled water | 20 to 30 cents | around 900 euros |
| Branded water in glass | 50 to 80 cents | around 2,400 euros |
The Reverse osmosis calculator puts in your figures and shows after how many months the system has paid for itself.
Who it pays off for
For households that currently buy bottled water and drink or cook with at least three litres a day. Then the system is cheaper after two to three years, and it saves carrying crates and cuts plastic. For households with lead pipes, well water containing nitrate or very hard water, the sums are secondary: there, reverse osmosis is a solution that other filters do not offer. For everyone who already drinks tap water and is happy with it, reverse osmosis never pays off financially.
What you should set against it
Reverse osmosis water is low in minerals. If you have been drinking calcium- or magnesium-rich mineral water, you lose that source. Remineralisation costs extra. And the system needs care: if you forget filter changes, after two years you have worse water than from the tap. What belongs to that is covered in Filter changes and maintenance.
Try it out
Reverse osmosis calculatorSystem, filters and wastewater against bottled water: cost per litre and payback in months.Plastic savings calculatorHow many bottles, how much plastic, how much money and CO2 you save per year if you switch.Frequently asked questions
Is a reverse osmosis system possible in a rented flat?
Countertop units yes, with no intervention. Under-sink systems with a three-way tap can be removed again, and many landlords agree. Ask first and take photos of the original state.
How long does a system last?
Housing, pump and tap fitting 10 to 15 years. Filters and membrane are wear parts.
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