What a Building’s Hot Water Load Profile Looks Like


One of the services Renewable Design Associates offers is determining a facility’s hot water demand.  This can be part of solar design, or efficiency measures in general.  An important part of this process is, whenever possible, collecting data with a flow meter.  This information is not only important for determining how much water is used, but when.  For example, if you were to monitor hot water usage for two weeks and produced a total number of 14000 gallons, it would be easy to assume a daily average of 1000 gallons.  However, let’s say your facility is a gym with a commercial laundry.  People workout and shower every day, which creates a small hot water load.  However, 90% of your load comes from a commercial laundry facility in the building which operates 4 days a week.

Here is an example of output from a recent demand study we did for a solar thermal design:


Using data analysis software, we can extract important data for time of use trending, maximum flow rate, etc. down to nearly every second.  Here we’ve zoomed in to a single day:


 We typically use highly accurate ultrasonic flow meters, which are non-invasive, to collect the data.  We are able to see great detail, even let people know if they are routinely leaving faucets on at night (which happens more than you’d think!)  Picking the right flow meter is important too—many months of research and trials went into our decision on which meters to acquire.

The main reason we at Renewable Design Associates are concerned with this load profile is for sizing Solar Thermal systems.  Time, and day, of use is a very important part of determining not only panel count, but the size of our thermal storage tank.  This is important in making sure you maximize efficiency of your system.

If you have questions or would like to learn more about your hot water demand, get in touch with us!