Water Saving - Home
Using water at home—to shower, do laundry, soak plants—consumes energy. It takes energy to clean and transport water, to heat it if need be, and to handle wastewater after use. Hot water is responsible for a quarter of residential energy use worldwide. Efficiency can be improved household-by-household and tap-by-tap.
In the United States, 60 percent of home water use occurs indoors, primarily for toilets, clothes washers, showers, and faucets. Low-flush toilets and efficient washing machines can reduce water use by 19 and 17 percent respectively. Low-flow faucets and showerheads and efficient dishwashers can also contribute. In total, these technologies can reduce water use within homes by 45 percent.
30 percent of home water use occurs outdoors, while another 10 percent is lost to leaks. Water use for irrigation can be reduced or eliminated by using captured rainwater, shifting to plants that do not require it, installing drip irrigation, or turning off the spigot entirely.
Local restrictions on water consumption and policies requiring efficient plumbing are highly effective. Product labeling can inform consumer choices, while incentives, namely rebates on purchases of efficient appliances and fixtures, can encourage voluntary action.
Hot water…residential energy use: Ürge-Vorsatz, Diana, et al. “Heating and Cooling Energy Trends and Drivers in Buildings.” Renewable and Sustainable Energy Reviews 41 (2015): 85-98.
average American…water [use] each day: Kenny, J. F., et al. Estimated Use of Water in the United States in 2005. U.S. Geological Survey Circular 1344, 2009.
used indoors…outdoors…lost to leaks: Inskeep, Benjamin D., and Shahzeen Z. Attari. “The Water Short List: The Most Effective Actions U.S. Households Can Take to Curb Water Use.” Environment. July-August 2014.
[efficient] toilets and…washing machines: Inskeep and Attari, “Short List.”
[impact of] efficient appliances and…fixtures: Inskeep and Attari, “Short List.”
older toilet [vs.] efficient one: NRDC. Water Efficiency Saves Energy. New York: Natural Resources Defense Council, 2009.
behaviors…[that] reduce water use: Inskeep and Attari, “Short List.”
struggl[es] with water availability: Padowski, J., and J. Jawitz. “Water Availability and the Vulnerability of 225 Large Cities in the United States.” Water Resources Research 48 (2012): 1-16.
Nuclear and fossil fuel plants…water for cooling: Maupin, M.A., et al. Estimated Use of Water in the United States in 2010. U.S. Geological Survey Circular 1405, 2014.
invisible gallons associated with [electricity]: NRDC, Water Efficiency.
Water Saving - Home
Project Drawdown defines water saving - home as: the use of low-flow fixtures and pressure regulators in the household. This solution replaces the use of conventional taps and showerheads.
To determine the overall impact of water saving in the home, an analysis of low-flow taps and showerheads was undertaken to estimate the worldwide domestic water savings, energy savings, and greenhouse gas emissions reductions in high-growth scenarios of adoption of these devices. Other water saving measures in the home – such as low-flow toilets, washing machines, etc. – may also provide marginal energy savings, but these were not included to simplify the analysis. Taps and showerheads were examined because they are relatively cheap to implement, pose minimal challenges when retrofitting, and can significantly reduce water and energy consumption.
Total Addressable Market 
This estimate takes into account a growing world population, increasing wealth, and national wealth distributions. The total addressable market is the total amount of residential water demanded globally for populations with a gross domestic product per capita of at least 10,000 international dollars,  and amounts to 139 trillion liters per year. Populations with lower wealth generally use much less water: in some cases they have no pipe-borne water to their homes, and for 20% of the world’s population water is not even available at community standpipes. Therefore, water-saving devices, which assume pipe-borne water, are not considered for these populations in this analysis.
For the target market, however, 54 percent of existing faucets and showerheads were taken as low-flow devices in 2014: that is the current adoption.  This is based on a survey of 10,000 residents in 10 countries of the Organization for Economic Cooperation and Development (OECD).
Adoption Scenarios 
The main drivers of adoption of low-flow taps and showerheads were assumed to be population and wealth, as indicated earlier. Adoption of these devices can increase in two ways – replacement of high-flow devices for the remaining 46 percent of the market (retrofitting), and increasing the number of people above the minimum wealth threshold (rising wealth). Retrofitting was assumed to occur entirely within the first 4 years of analysis (2015-2018).
Impacts of increased adoption of water saving (home) from 2020-2050 were generated based on three growth scenarios, which were assessed in comparison to a Reference Scenario where the solution’s market share was fixed at the current levels.
- Plausible Scenario: In this scenario, 95 percent of the possible increase is captured, and low-flow devices are assumed to save 12.75 percent of water, based on the average of 3 sources: the United Nations (2006), Kaps & Wolf (2011), and Gleick et al (2003).
- Drawdown Scenario: This scenario is similar to the Plausible Scenario, but the water savings are increased to one standard deviation above the mean.
- Optimum Scenario: In this scenario, adoption of water saving (home) is assumed to be 100% of the possible increase.
Grid emissions were captured assuming that all water heating was done by electric heaters, and that less water used meant less water heated. For this, grid emissions factors guided by the Intergovernmental Panel on Climate Change (IPCC) were used.
Purchase costs for adoption of low-flow fixtures were estimated using 30 data points, and combined with 4 data points on professional installation costs to estimate the total first costs at US$28 per low-flow fixture.  Operating cost differences were averaged from 9 data points and were assigned to the conventional fixtures, with operating costs for the solution kept at 0. This represented the cost difference only, and included the cost of the water saved.
The results of the Plausible Scenario suggest that the greenhouse gas abatement potential is significant, with an avoided 4.6 gigatons of carbon dioxide-equivalent gases from 2020-2050. This translates to an atmospheric greenhouse gas reduction of 0.39 parts per million of carbon dioxide by 2050. The analysis indicates that the energy required to heat water in the home is approximately 20-120 times greater than the energy embodied in district water supplies (and sanitation services) when the water supply is of a modern standard. In the Plausible Scenario – with 95 percent adoption of low-flow taps and showerheads – even with a net cost of US$72 billion, the operating savings are roughly US$1.8 trillion due to water cost savings.
Given that there could be a tremendous increase in domestic water demand over the coming 30 years (demand is forecast to increase by 270%) the implementation of the water saving – home solution appears very reasonable, especially as the cost of retrofitting existing taps/showers is not great. A co‐benefit of domestic water saving is a reduced reliance on over-stretched freshwater supplies, reduced energy consumption, and reduced need for new water and energy infrastructure. Water and energy supply are two essential services that crossover in what is called the ‘water-energy nexus’.
 For more on the Total Addressable Market for the Materials Sector, click the Sector Summary: Materials link below.
 The international dollar is a consistent currency used for comparisons across countries and years.
 Current adoption is defined as the amount of functional demand supplied by the solution in the base year of study. This study uses 2014 as the base year due to the availability of global adoption data for all Project Drawdown solutions evaluated.
 For more on Project Drawdown’s three growth scenarios, click the Scenarios link below. For information on Materials Sector-specific scenarios, click the Sector Summary: Materials link.
 All monetary values are presented in US2014$.
Full models and technical reports coming in late 2017.