Waste Water Heat Recovery Systems

What is a WWHRS and how does it work?

Typically, a waste water heat recovery system works by extracting the heat from the water your shower or bath sends down the drain. This heat is used to warm the incoming mains water, reducing the strain on your boiler and the energy required to heat your water up to temperature. A system normally takes the form of a long vertical copper pipe, where the warm water runs alongside the colder mains water to exchange the heat.

The devices are typically around 60% efficient, so they convert 60% of the potential energy in the waste water back into heat for the incoming water. This can save you money on your bills, especially if you use a lot of hot water in your home. The payback period – as we will discuss – is another matter.

The good news is that it is a fairly simple device. It has no electrical components, no pumps or controllers, and so it requires very little maintenance. It has an expected lifespan of 20 years+. Unfortunately they are usually a little too expensive for the payback they generate in domestic dwellings, but this is beginning to change.

Is it worth retrofitting a WWHRS?

In some cases retrofitting may be possible, but the bulk and length of the recovery device means that most showers or baths wouldn’t be suitable. It is much easier to get it installed when you are fitting a new bathroom.

How much do they cost?

They typically start at around £600 + installation. So you are looking at over a £1,000 to get a unit in your home.

Are they worth it?

Until 2015, installers often used WWHRSs as a means to get a new home up to Sustainable Homes Code standards, rather than a means to save money. Now that the Sustainable Homes Code is no longer around, although you certainly will save some cash with a WWHRS, the payback period is not worthwhile for most people.

A typical saving on an average home might be £20-30 a year. So the payback time is around 40 years typically. Of course, if you use a lot of hot water, it can begin to look a bit more attractive.

Other ways to recover wasted heat

There really are better ways to cut your bills – reducing your hot water use is a great way to cut your bills. That means less time in the shower, fewer baths and using a dishwasher instead of washing up under running hot water. Doing fewer hot washes in your washing machine will also cut your energy use. This is a much better way to save £20 a year, instead of installing an expensive appliance like this.


    • Saves some money on your bills by extracting the heat from your waste water.


    • Can’t be easily retrofitted, only really viable on a new build property.
    • Not normally cost-effective.


    • About £1,000.