Quantifying carbon emissions from water use in the home

The Environment Agency in collaboration with the Energy Saving Trust has carried out a research project to understand carbon emissions from water use in the home and the potential for savings.

Our report ‘Quantifying the energy and carbon effects of water saving’ sets out the key findings and recommendations from this research.  Download from the links below.

• Summary report: Quantifying the energy and carbon effects of water saving (PDF, 2.04MB)

Background

In the UK, we use approximately 150 litres of water per person per day in our homes. Our previous research indicates that when household and water company emissions are considered together, around 90% of these emissions (35 million tonnes CO_²  per year) can be attributed to ‘water in the home’. This includes energy for heating water but excludes space/central heating. The remaining 10% of emissions originate from abstracting, treating and supplying water, and subsequent wastewater treatment. For this reason, it's important to better understand the effects of water use on domestic CO^₂ emissions.

The study identifies a number of key findings both for existing households and new build dwellings as well as for our own water use behaviour in the home.

Key findings

• Hot water use is higher in current new build dwellings due to an increase in shower use. This means, despite increases in boiler efficiency and decreases in water use for flushing toilets, CO^₂ emissions are not significantly lower than in existing homes
• For existing homes, the majority of CO^₂ emissions are from home heating (77% home heating, 23% water heating) however in current new build dwellings, CO^₂ emissions from hot water use will far exceed those from home heating (72% for water, 28% for space heating in zero carbon homes) if attempts to increase energy efficiency are successful but not accompanied by equivalent increases in hot water efficiency
• Water efficient retrofit devices that save hot water can save more CO^₂ than cold water retrofits but all result in water and financial savings

Recommendations

• Energy efficiency retrofit programmes for existing homes should incorporate water efficiency measures, because they can save water, reduce energy use and lower carbon dioxide emissions
• Regulatory framework for hot water system design should be reviewed to incorporate a similar level of detail to that given to building and ventilation design
• From a consumer perspective, simple changes such as spending less time in the shower can lower energy bills, save money and cut emissions.