How Much Does a Water Softener Cost to Run in the UK?

Thinking about installing a water softener? You’ve probably wondered, “How Much Does a Water Softener Cost to Run in the UK 💧 ??”

It's a great question — because while soft water has many benefits (no more limescale, softer skin, longer-lasting appliances), it’s worth knowing how much it’ll cost to maintain your system.

In this guide, we break down the real-world costs of running a Harvey TwinTec S4 water softener — one of the UK’s most popular and efficient models. We’ll look at water usage, salt requirements, and give you a real example calculation to help you budget with confidence.

Electricity Costs

£0

The Harvey TwinTec is a non-electric system. So unlike electric softeners - electricity wont contribute to the running costs.

🚿 Water Usage & Costs in the UK

How much water does a water softener use?

The Harvey TwinTec S4 is known for being one of the most water-efficient water softeners available in the UK. Every time it regenerates (cleans itself to stay effective), it uses about:

17 litres of water

Thanks to its twin-cylinder design, it only regenerates when needed, and never while you’re using water — making it both smart and efficient.

What does that cost in water bills?

UK households currently pay an average of £2.00 per cubic metre of water (1,000 litres). That means each regeneration costs:

17L = 0.017 m³
0.017 m³ × £2.00 = just 3.4p per regeneration

Even if your softener regenerates once a week, that’s under £2 per year in water costs.

🧂 Salt Usage Per Person & Cost of Block Salt

How much salt does a Harvey Water Softener use?

Salt is the main consumable your water softener needs. The Harvey S4 uses standard block salt, which is clean, easy to handle, and widely available. Based on manufacturer data and installer feedback:

Each pack of block salt contains 2 x 4kg of salt blocks.
On average each home uses around 1 block per person per month.
So a 2-person household uses about 24 × 4kg salt blocks per year. Which is 12 packs of salt.

Of course, heavier water usage (e.g., large families or homes with power showers) may affect the rate.

What does block salt cost?

Block salt comes in handy 8kg twin-packs and prices vary slightly depending on if you buy packs in bulk (you can purchase salt here online in packs of 3, 6, 9, 12, 18, 21). Here’s a typical breakdown:

£7.42 - £8.66 per pack of 2 x 4kg blocks
Multi-pack deals may lower that to around £7.42 per pack

Example:

For a 2 person household: 12 packs × £7.42 = £89 per year, £44.57 per person.

💷 Additional Example Running Cost Calculation

Let’s walk through a typical example:

👨👩👧 Family of 3

Salt usage:
36 blocks - 18 packs × £7.42 = £133.56 per year
Water usage (17L per regen × 52 weeks):
884L = 0.884 m³
0.884 × £2.00 = £1.76 per year

✅ Total annual cost:

£133.56(salt) + £1.76 (water) = £135.32/year

💡 Monthly cost:

£135.32 ÷ 12 = £11.28/month (probably less than 2 x oat milk lattes from Starbucks)

🌟 Why the Harvey TwinTec S4 Is So Cost-Efficient

The Harvey S4, available from NE Water Softeners, is designed for low running costs and maximum efficiency:

Only uses 300g of salt per regeneration. (to put this in perspective - some models like Water2Buy can use up to 4.5kg of salt per single regeneration. Hence why they can cost you more in the long run).
Regenerates with just 17 litres of water.
Twin-tank design ensures zero downtime and better performance.
No electricity needed — it's powered by water pressure alone.

When compared with other models (like the Kinetico Premier Compact), the S4 offers equal or better performance while using less salt and water per cycle — saving you money over time.

Final Thoughts: Is a Water Softener Expensive to Run?

Not at all. With a Harvey TwinTec S4, most UK homes can expect to spend less than £12 per month to enjoy the benefits of soft water. That’s less than the price of a a daily Costa Coffee or Starbuck trip — and it protects your home and boiler from long term damage, improves your skin & hair, and saves money on cleaning products.

So if you're looking for a reliable, low-cost way to combat limescale and enjoy softer water, a Harvey TwinTec system is a great choice.