As societies around the world become more aware of just how finite the Earth’s natural resources are, talk of living “off-grid” is growing. This “grid” refers to the networks of pipes and cables that deliver electricity, natural gas, running water, and other utilities to homes in urban areas. Off-grid living is by no means a new idea; people have lived throughout most of history without these conveniences, and many still do. Some do it because they live in rural areas where it wouldn’t be practical to connect to a grid since neighbors live so far away. Other pursue off-grid living because they reside in a place that doesn’t have the means to build this kind of infrastructure, financially or practically. Increasingly though, people opt to live off-grid as a conscious environmental choice.

Whatever the reason, it is still possible to live off-grid using renewable and sustainable resources without sacrificing too much of the convenience of being connected to a public source. For instance, home-based solar and wind energy is becoming more affordable and can provide electricity for lighting, heating, cooling, and cooking. It is also possible to design buildings using passive systems of strategically-placed windows and openings to heat, cool, and light a house without any electricity or natural gas.

These sustainable practices can be accomplished in almost any home on Earth, regardless of geography. However, the game changes when it comes to one vital resource: water. Perhaps the most geographically volatile of all essential resources, water, ultimately in the form of precipitation, can present perhaps the biggest hurdle to accomplish a truly self-sustaining lifestyle.

While civic water infrastructure often relies upon extraction from bodies of water like rivers, lakes, or underground aquifers, personal water sources need to come on-site. Short of digging a well (which would be legally and functionally challenging in most urban locations), the only method of doing this is rainwater harvesting.

With water shortages expected in the majority of states over the course of the next decade, water scarcity is becoming a growing reality in the United States. California is in severe drought, the Great Plains are draining the groundwater of the Ogallala Aquifer at an alarming rate, and the Colorado River basin lost the equivalent of two years’ worth of water runoff in a single year. This makes water conservation an essential issue that will have to be solved in the near future or else run the risk of devastating widespread shortages.

The average American uses 80-100 gallons of water per day for household purposes such as drinking, bathing, and cooking. However, this number inflates quickly if appliances are older and less efficient. Fortunately, there are many ways to cut back on the amount of water used at home. Rainwater can be collected from non-permeable surfaces such as rooftops and pavement, then filtered and reused for various end-uses at home, including both interior and exterior (Burns et al. 2015). Greywater systems collect water from interior water fixtures and appliances such as faucets, baths, and showers. After filtration, this water can be pumped back into the house for non-potable use in washing machines and toilets, saving on average 28% in total water use (Ghisi et al. 2007). Additionally, low-flow fixtures such as faucets, shower heads, and toilets, as well as high-efficiency washing machines, can reduce the amount of water used at home up to 30% (Environmental Protection Agency 2015).

No matter the efficiency of home water systems, they will still require at least some amount of water input. This is where rainwater harvesting becomes so essential. One of the simplest rainwater harvesting systems is to collect runoff from the roof by directing the gutters to a rain barrel or other large capacity vessel. A spigot on the rain barrel can then be attached to a hose and the rainwater can be used for irrigation in the yard or garden. 

This requires almost no technical knowledge to set up and there are no pumps, filters, or other mechanical systems.

It is also possible to collect runoff from the roof and pipe it through a filtration system that will produce water clean enough to use for flushing toilets and washing clothes. Although, the water is non-potable and cannot be used for cooking. These systems are more complex and costlier than rain barrel systems, though there are cool and sustainable ways to do it.

Kroon Hall at Yale University actually uses an adjacent pond for rainwater harvesting and filters it using aquatic plants. This water can then be used to irrigate the landscaping or be pumped back through the building for non-potable uses.

This kind of system can even be taken a step further by filtering the water at a higher standard so that it is potable. This means it can go toward all household uses including drinking and cooking. There are various home systems available that do this from companies like RainHarvest Systems and BRAE.

It’s important to note that the amount of water it is possible to collect is limited by the size of the roof being used to collect the water, the capacity of the storage tank, and (not surprisingly) the amount of rainfall. Places with lower levels of precipitation will require a larger surface area for collection than a place with more precipitation.

Another factor to consider is that some locations have very seasonal precipitation which limits when the rainwater can be collected. In colder climates, precipitation will come in the form of snow which will have some loss due to wind and cannot be collected until it melts. In other places, such as Mumbai, the precipitation levels skyrocket during monsoon season and then drop off to almost nothing for the rest of the year. This means a rainwater harvesting system would need enough capacity to store up enough water to make it half the year until rainfall resumes, rather than just enough to be incrementally used as it is collected.

Despite these challenges, rainwater harvesting likely represents one of the most key future endeavors for sustainable homes. Many locations throughout the world could find that rainwater harvesting is already possible whereas others will face climatological obstacles. In the face of looming global water shortages, the need for rainwater harvesting systems, as well as higher efficiency systems, will only push these technologies forward.