Actual costs and savings may vary from household to household depending on a number of factors, so although every effort has been made to provide an accurate depiction of the potential savings, Methven UK accepts no liability with regards to the level of savings that are actually achieved.

Flow rates

The water savings calculator compares the selected handset flow rate against an average UK shower flow rate of 15 litres per minute (l/min).

1. Developer Part G calculations compare a standard 15 l/min handset with the Kiri Low Flow handset (5.5 l/min).
2. Homeowner calculations compare a standard 15 l/min handset with the Aurajet Aio handset (8 l/min).
3. Shower heads are tested at a working pressure of 3.0 bar.

Energy usage

Hot water is assumed to be supplied by an A-rated gas combi boiler. Boiler efficiency reflects typical modern UK combi boilers and assumes well-insulated pipework between the boiler and shower.

1. Boiler efficiency: 85% (typical range 70–92%)

Gas cost estimate

Based on Ofgem domestic energy price-cap average UK gas unit rates (2025–2026).

1. Gas unit rate: £0.07000 per kWh

Source: Ofgem energy price cap and typical UK household unit rates

https://www.ofgem.gov.uk

Water cost estimate

Based on Ofwat UK average household water and sewerage charges (2025–2026) using typical metered tariffs across England and Wales.

1. Water + sewerage: £3.75 per m³
2. Cost per litre: £0.00375

Sources:

Ofwat average household bills 2025–2026

https://www.ofgem.gov.uk

UK water company tariff data (2025–2026)

Carbon footprint

Relevant emissions factors for natural gas heating:

1. CO₂e per kWh of heat from a gas boiler: 0.21 kg

Source: UK Government/DESNZ emissions factors and industry data.

Energy savings calculation assumptions

Assumptions have been made about typical UK shower usage:

1. Shower outlet temperature: 40 °C
2. Cold inlet temperature: 10 °C
3. Hot inlet temperature: 60 °C
4. Energy required to heat 1 litre from 10 °C to 60 °C: 209,300 J
5. Average UK household occupancy: 2.36 people
   Source: ONS Census data
6. Average shower duration: 11 minutes
   Source: Bathroom Association 2022 research

Most UK homeowners shower at least once per day.