skip to primary navigationskip to content

MPhil in Engineering for Sustainable Development

global challenges, engineering solutions

Studying at Cambridge

Cherno Lamin Jallow

Are grey water heat recovery systems financially viable? – A case study in Robinson College

Households use significant amounts of energy to heat water. The domestic energy consumption for hot water can be significantly minimized through the installation of a Grey Water Heat Recovery System (GWHRS). GWHRS extracts heat from wastewater and uses the recovered thermal energy to instantly heat incoming cold water.


The supply of hot water for showers by electric heaters or steam boilers is financially and environmentally costly in terms of energy bills and greenhouse gas emissions. It is thus necessary to investigate the possibility of reducing energy consumption for showers through the installation of GWHRS. The payback calculation model adopted in this research will help decision makers to assess the financial feasibility of integrating such a system in the hot water supply stream and eliminate any doubts regarding the application of a GWHRS in the water supply system.


Furthermore, this paper discusses the different options available and also attempts to evaluate the financial viability of installing a GWHRS either at a heat point source (individual) or at a wastewater pipe (On-site). Robinson College was used as a case study to provide an opportunity to explore the concept in detail.


To this end, the research discovered that installing an individual GWHRS is only viable at shared showering facilities adjacent to the boiler as it decreases the high capital investment. It further confirmed that a holistic approach performs better than individual measures which have very little impact.