Posted by: Geoff Jones on May 19, 2009
There are many reasons that people choose to install Solar Domestic Hot Water systems today, one of them being the environmental benefits, but many people still wonder how much it will save them on their utility bills once it's up and running. Although there is no magic way to come up with an exact number for everyone due to varying factors in each home let's take a quick look. Based on some statistics available today we should be able to get a rough idea of the potential savings.
According to statistics from Natural Resources Canada, on average, water heating represents about 20% of the energy use within a typical home. A lot of marketing material and articles in North America claim that water heating typically represents 20-30% and it will vary from home to home based on the technologies in your home as well as your water use patterns.
Looking at a number of manufacturers of SDHW systems the published savings potential is typically between 40%-80%. So let's stay on the lower end of that for the sake of our discussion and assume that a Solar Domestic Hot Water (SDHW) system can typically reduce your hot water heating needs by 50%. In this case a system would reduce the portion of your energy bill (gas, electric, or propane etc.) that is attributed to hot water heating, by 50%.
Let's take a quick look at a simple example.
Our hot water tank is natural gas and the only other natural gas appliance within our home is our furnace. Knowing that we don't run the furnace during the summer months we can use our natural gas consumption for say June, July, and August to give us a pretty good idea of what our hot water heating costs are. Sure, we might use a little more hot water in the winter but this is just to give us a ball park and you can always add a percentage to account for higher usage during colder months.
So, looking at my natural gas usage during the summer of 2008 we have:
- June 15 - July 15: 30.691m3
- July 15 - Aug 15: 36.631m3
- Aug 15 - Sept 15: 36.631m3
The average consumption for these 3 billing periods was 34.651m3. This is probably a pretty good representation of natural gas use for hot water heating as the furnace would not be in operation during these 3 warmest months of the year and we can see the relative consistency of the consumption as well. Total annual consumption for 2008 was 1647.394m3. So if we assume that our gas usage for hot water heating is relatively constant through-out the year we have a total annual consumption of 34.651*12months=415.812m3 for hot water heating.
This is about 25% of our total annual gas demand of 1647.394m3. According to the stats above we can see that we are in the 20%-30% range that is often discussed.
So, if an SDHW system saves 50% of our hot water heating costs this would represent a total annual savings of:
415.812m3 * 50% savings * $0.35109 gas rate per m3 = $72.99
Using this approach we can also easily calculate the best and worst case savings just by changing the percentage of hot water heating we think (or a professional in your area with expertise thinks) the SDHW system will address.
This is just one example and does not necessarily represent the savings you will see yourself. Savings will vary from region to region and from home to home based on a number of factors. For example; in a home where the occupants take longer showers or have larger bath tubs etc. their hot water usage will be higher, as will the potential savings. Other factors include the system efficiency, sizing, your fuel type (electric hot water tanks generally cost more than natural gas to operate so the savings potential is greater) and your geographic location which affects the solar energy potential through-out the year.
It's also important to remember that although it's nice to save money, and we all like to do it, these technologies are not just about saving money. I'm not saying you should throw around money just for the sake of spending it. However, in addition to the potential savings in operating costs these technologies can also help reduce our impact on the environment. With continued adoption of alternative technologies like SDHW, and many others, these technologies will continue to improve and with greater adoption and volumes prices should come down. Who knows, maybe it won't be that long before these types of technologies are standard components in new home construction.