Addressing the ROI of rainwater harvesting
31 Jan, 2012 By: Christine Hawkins i-news
When discussing rainwater harvesting with my customers who serve the residential market, the first question I am often asked pertains to the return on investment:
If a system is installed, how many years will it take until a customer can collect enough water to offset the cost of the installation?
The short answer is more than 100 years. This is usually because the retail price of water is low in many areas. But, the true concern about ROI is not what will I save, but what will I get? Customers often feel greater sticker shock for their systems because they have not examined their expectations and misconceptions about how much water is actually used, and where. As our nation has developed from wild lands to agricultural belts, and now into increasingly large urban centers, the way we think about water as a resource needs to change.
Return on investment is difficult to calculate for rainwater, because what we are doing in the landscape is generating green spaces to enhance our quality of life, not to generate a cash crop. Much of what we gain from our green spaces is measurable only by subjective metrics: playing catch with the grandkids on the lawn, listening to the soothing rustle of leaves on a summer day, the scent of flowers through an open window, gathering for a picnic or smelling the roses.
Green spaces are a part of being human, and living without them reduces us to robots, or worse, zombies! Therefore, ROI is not usually the driving factor for a residential customer to adopt rainwater harvesting. What rain harvesters understand is that the benefits to their community development, personal water security, and environmental impact far outweigh the initial costs of the system.
Managing expectations
To answer the question of ROI, the inputs and outputs need to be considered. Let's start with the outputs, or expectations of the system. What purpose will the water have? If it's irrigation, how many square feet do you wish to irrigate? Managing expectations is the first part of a successful rainwater harvesting system. Will the water be used for a few pots of herbs? Will it need to top off a large koi pond? Does the customer want to disconnect landscape water completely from the potable supply?
These expectations will start the discussion about ROI, and size of the system. The customer with a few pots of herbs will not likely need a 5,000-gal. tank, and likely the customer with the koi pond is going to need something a bit more complex than a simple rain barrel at a downspout. In the arid regions of California, rainwater is often used to irrigate a particular section of plant material, such as edibles, or serves as an alternative water source during times of peak need.
Design considerations
After answering questions and setting reasonable expectations, the focus shifts to design. What size of tanks will be needed? What is the size of the roof space? What is the size of area you can dedicate to storage tanks, either above ground or below? These are more complex questions.
The ability of your roof to provide for your lawn depends heavily on the ratio of roof space to rainfall to square feet of turf. To determine how much landscape can be serviced, or how much roof you will need to harvest from, use the following equation:
Roof x Rain = Turf x ET
Plug in your numbers and solve: Square feet of roof multiplied by inches of expected rainfall per year equals square feet of turf multiplied by inches of evapotranspiration (ET) per year.
The size of your retention basin, tank, or reservoir is a more complex calculation, based on the timing of the rainfall and the peak ET rates of your landscape. You will need to have enough water held in reserve to irrigate from the last of the spring rains to the first of the fall rains, unless you live in the desert where summer monsoons will replenish your supply on a regular basis.
The essential conversation
After you have had a conversation with your customer about expectations, set some reasonable goals and determine whether the capacity of the roof space combined with annual rainfall can, with the right system, actually provide enough water for the intended landscape target. It is tempting at this point to break out the graph paper and slide rule and begin to lay out the details of the system, including piping, filters, pumps, tanks, and fittings. But before you go to the trouble, first determine from the client how much buy-in they have into this project at this point.
You know going into it that water is cheap and, in most times, plentiful. You know tanks and pumps are not cheap, and are likely to cause the ROI of the project to be greater than the expected lifetime of the house. Before you get into numbers, engineering, or worse, a bid, talk to you customer a little more. Determine a list of pros and cons.
Start with what benefits the customer will see. Is it healthier water for the vegetables? An offset of potable water use in the summer? Reduced runoff to neighboring properties? Then describe some of the details. Include things like tanks above or below ground, visible filtration systems and increased piping along the house lines. Discuss the benefits, future maintenance and possibilities for alternative sizing options depending on budget and expectations. A list of pros and cons is essential when you present numbers to the client. Without it, they lack the framework to judge the worth of the work.
Calculating the ROI of a rainwater harvesting system in 10 minutes or less:
- Discuss expectations. For what will the water be used? Ask a few directed questions and set up the customer’s expectations to be in line with site capacity.
- Determine whether supply is adequate. Expectations may need to be adjusted to suit the ability to collect and store the available rainfall. This will require a few simple calculations based on the regional rainfall, square footage of roof and landscape, and available area for storage.
- Run the list of pros and cons. Sometimes this is complex. Reasons can be as varied as simply keeping up with the Joneses to complying with local building codes requiring stormwater retention. Pros and cons must be listed and evaluated by the customer, with the customer, so that trust is built and they are emotionally invested in the project.
In 10 minutes, you and your customer have evaluated whether or not the conversation should be continued. Should plans be drawn, engineers be consulted, or a formal bid put together? If they want you to work up a quote, which will take more time, at least you have established a baseline for expectations so that the customer does not experience sticker shock. In common sales parlance, this is called “meeting the objection.”
Balance the proposal with the list of pros and cons which had been discussed. Sure, some may balk, but wouldn’t you rather weed those out quickly? Don’t let a request for an ROI scare you away from selling a rainwater harvest system. Sometimes the numbers are not enough, but with a few simple questions, the customer can be opened to new possibilities for alternative water to enhance their green spaces.
Please send any technical comments or questions to our webmaster.