Reverse osmosis is worth buying for specific reasons and poor value bought on a general feeling that the water could be better. The way to settle it is to name what you want to change, then check whether a membrane is the thing that changes it. Three answers come out of that, and only one of them is yes.
Where it clearly pays
Two cases justify it easily. The first is a laboratory result showing a dissolved contaminant that reverse osmosis removes and that matters when swallowed, which is a health decision rather than an economic one. The second is a household already buying bottled water for drinking and cooking: an under sink system with annual prefilters and an occasional membrane costs far less over a few years than carrying bottles, and it removes the storage, the trips and the packaging. If either applies, the answer is usually yes and the payback is straightforward.
Where it is the wrong purchase
If the complaint is scale on the kettle, spotting on glassware, poor lather or dry skin, that is hardness and a softener is the correct equipment. An under sink membrane treats one tap and leaves every shower, appliance and washing machine exactly as they were. If the complaint is chlorine taste alone, a carbon filter does that job for a fraction of the price and without a reject stream. Buying RO for either of those is spending well and fixing nothing, and it is the most common regret in domestic water treatment.
The costs people forget to count
Beyond the purchase there is installation, which may include drilling a worktop and fitting a drain saddle. There are prefilters annually and a membrane every few years. There is a reject stream running whenever the system produces. There is cabinet space taken by a tank. And there is a small ongoing attention cost: a system whose filters are never changed stops performing and eventually becomes worse than no system. None of these is large, but they should be in the arithmetic when comparing against a simple carbon filter.
How to decide in an afternoon
Read your utility's annual report, or test if you are on a well. Write down the one thing you want to be different. If that thing is a dissolved contaminant, or the taste of drinking water, or an end to buying bottles, reverse osmosis is worth it and an under sink system is the format. If it is scale, soap or skin, buy a softener instead. If it is chlorine smell in the shower, buy a whole house carbon filter. Our whole house RO guide covers the much larger question of treating everything by membrane.
Questions people ask about is a reverse osmosis system worth it
Is reverse osmosis worth it if my water already tastes fine?
Probably not, unless a test found a specific contaminant it removes. Taste is the most common reason people buy it and the easiest to satisfy with carbon.
Will it stop limescale in the kettle?
Only for water drawn from the RO tap. It treats one tap, so every appliance fed by the ordinary supply still scales. That is a softener's job.
Does it work out cheaper than bottled water?
For a household that regularly buys bottled water for drinking and cooking, yes, and usually within a couple of years including filter changes.
What ongoing costs should I expect?
Prefilters annually, a membrane every few years, a reject stream while it produces, and the attention to actually change the filters on time.