What is the payback time for a rainwater harvesting system?

Rainwater harvesting systems can have a payback time of up to 15 years. However, this will depend on the amount of rainfall, water needed and building.

rainwater harvesting systems

The current payback period for a rainwater harvesting system is around 15 years. This article will give an idea of system costs, and whether you will benefit in the long run from installing a rainwater harvesting system.


Cost of a rainwater harvesting system:

Including installation an entire system could cost from £2500 to £4000. The newer your property the lower the cost of installation. The price can be as low as £1000 in some cases. There are additional payments for the plumbing works, also excavation and commissioning of the control appliance.


What is the payback period?

The payback of a residential system can take up to 15 year.  However, the payback of a commercial system can be as quick as 3 years.

Each application is different, but larger roof areas do tend to capture more rainfall. Buildings with a higher demand and larger roof will provide the shortest payback period. In comparison with other renewable technologies rainwater harvesting does tend to offer the shortest payback period.


Costs throughout the life of the system:

A rainwater harvesting system does require different components which differ from a standard water supply system. These components will result in an overall higher cost. In order to determine if future water cost savings can offset the higher capital costs, you will need to analyse the cost over a systems life.

The following factors will have an influence over the outcome:

  • Amount of rainfall
  • Amount of water used
  • Type of building


Amount of rainfall that can you collect:

The average amount of rainfall does tend to vary. The average amount for England is around 900mm. The highest average amount of rainfall in Wales is recorded to be in the central upland spine from Snowdonia to the Brecon Beacons, as these are the wettest areas.


Amount of water that is used daily:

The amount of water used on a daily basis, also varies across the UK. Although it is possible for the daily amount to be as low as 40 litres, the UK average tends to be around 150 litres per day per person. The lower the amount of water used in each household, the more likely the rainwater harvesting system will be able to supply the water for that demand.


The building:

As stated above a commercial building can be a better choice for a rainwater harvesting system. There is a far higher potential for cost efficiency than there is in a domestic property. Buildings such as offices and schools would be suitable as they have larger roofs and can therefore collect a considerable amount of rainfall. In addition, in some cases business may be able to claim Enhanced Capital Allowances for a rainwater harvesting system.


Image Sourced: Neil Palmer

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