Running cost is determined by hardness, household water consumption, the machine type, and how well it is configured. Metered machines cost substantially less to run than timer-based ones. There are real offsetting savings on detergent, appliance life and equipment protection.
What you are actually paying for
Three things, and only three:
- Salt. The dominant cost. The quantity is determined by how much hardness has to be removed, which is hardness multiplied by volume of water used.
- Water used in regeneration. Backwash, brine draw and rinse all go to drain. On a metered supply this is a real if modest cost; unmetered, it is free.
- Electricity, on metered electronic machines. Small – the unit is a controller and a valve motor, not a heater.
There is no consumable filter, no cartridge, and no chemical dosing. The resin lasts years and is not an annual cost.
The running cost depends on your hardness, your household’s water use, your salt price and whether you are metered – four variables that differ enormously between houses. Any single figure would be wrong for almost everybody, and we would rather explain the drivers than invent a number. See what things cost.
The four things that move it
1. Hardness
The harder the water, the more calcium and magnesium the resin has to hold per litre treated, so the sooner it exhausts and the more often it regenerates. Hardness is the single biggest multiplier and it is entirely outside your control – it is geology.
2. Household water consumption
The softener treats every litre that passes through it. A household of five uses considerably more than a household of two, so the resin exhausts sooner. Reducing water use reduces softener running cost proportionally, which is one of the less obvious benefits of fixing a leaking toilet.
3. Machine type
This is the one you control at purchase, and it matters a great deal.
| Type | Regenerates | Relative running cost |
|---|---|---|
| Timer | On a clock, regardless of use | Highest – regenerates when not needed, and can break through when use is high |
| Metered | When the measured volume treated reaches capacity | Substantially lower |
| Metered with proportional brining | Uses only as much brine as the actual exhaustion requires | Lower again |
| Twin cylinder metered | One softens while the other regenerates | Efficient, and no gap in supply |
4. How it is set up
A metered machine calculates its capacity from the hardness figure it has been given. Configured with a hardness higher than reality, it regenerates more often than necessary and wastes salt. Configured lower, it breaks through and hard water gets past. Setting it from your actual figure is free and it is frequently not done.
Reducing it
- Choose a metered machine. The single biggest lever, and it is decided at purchase.
- Set it from your real hardness figure, not a regional guess or a factory default.
- Set the household size correctly, and update it if the household changes.
- Buy salt in quantity. Price per kilogram falls substantially with volume, and salt keeps indefinitely if stored dry.
- Fix leaks. A running toilet is treated water going straight to drain, and you are paying to soften it.
- Do not soften what does not need it. The outside tap and, by regulation, the drinking tap should be on hard water anyway. There is no benefit to softening garden water.
- Keep it serviced, so the valve is sealing and the machine is not regenerating more than it needs to.
The other side of the ledger
A running cost assessment that only counts salt is incomplete. The offsetting savings are real, though they are diffuse and mostly show up as things not happening:
- Detergent and soap. Measurably less is needed in soft water to achieve the same result, across laundry, dishwashing, cleaning and personal washing. This is a continuous household saving.
- Appliance life. Washing machines, dishwashers and coffee machines all heat water and all scale. Soft water removes the mechanism entirely.
- Boiler and cylinder efficiency. A scaled heat exchanger or coil burns more fuel to deliver less heat, continuously.
- Component replacement. Immersion elements, plate heat exchangers, tap cartridges and shower heads all last substantially longer.
- Descaling products, and the time spent using them.
- Avoided failures. A plate heat exchanger replacement, or a burnt-out immersion element, is a real cost that softening makes much less likely.
We are deliberately not attaching numbers to those, for the same reason as above. But the direction is not in doubt, and in a house with a cylinder and high hot water use the equipment protection alone is the substantive argument.
When the sums do not work
Honestly: a softener is not automatically worth it.
- Very low hot water demand. A small flat with a combi used lightly does not present much surface for scale to form on.
- A property you are leaving soon. The payback is diffuse and slow.
- Where there is no drain or no space, and the installation would be a compromise.
- Where nobody will maintain it. A softener with no salt is an expensive piece of pipework.
- Where the only complaint is the kettle. Descaling a kettle occasionally is not a problem that justifies a softener.
In those situations a scale inhibitor protecting the boiler is frequently the proportionate answer – see softener or scale inhibitor.
Considering one? Get your actual hardness figure from your water company first – it drives the running cost and the machine settings.
Questions we get asked about this
How much does a water softener cost to run?
It depends on your hardness, your water use, your salt price and whether you are metered. We would rather explain the drivers than publish a figure that would be wrong for almost everybody. A metered machine set up correctly is substantially cheaper than a timer-based one.
Does a softener use a lot of water?
Some, during regeneration – backwash, brine draw and rinse. A modern metered machine regenerates only when needed, which keeps this modest. Timer-based machines regenerate whether or not they need to.
Will it save me money overall?
In a house with a hot water cylinder and reasonable demand, the equipment protection and detergent savings are real. In a small flat with light use, probably not. It depends on how much water you heat.
Does it use much electricity?
Very little. The unit runs a controller and a valve motor, not a heater. Some non-electric machines use water flow to operate entirely without power.
How often should it regenerate?
A metered machine decides for itself based on measured use, which is the point of having one. How often that turns out to be depends on your hardness and consumption.
Can I turn it off when we go away?
You can put it on bypass, though most metered machines will simply not regenerate if no water is being used. A long absence is worth thinking about for water stagnation reasons as much as for the softener.
Need this doing?
Call and describe the problem — you will speak to an engineer, not a call centre. Written quotes, no estimates over the phone.