How much Water does my Home use?

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Before you decide what kind of solar thermal system to install, you need to estimate your home's hot water use. There are two important parts to this equation: your actual water usage and your pattern of use. By changing the latter, you affect the former, so it's worth not only estimating but understanding how you and your family use water.

Surprisingly, even with all our modern technology and knowledge, there is still no reliable way to get a truly accurate view of precisely how much hot water any particular home uses. Instead, you'll have to rely on guesstimates, rules of thumb and inference.

Guesstimates and rough guides

There are a variety of hot water usage estimates available online and in published references. Though they all differ and cannot possibly be accurate for any particular family, most experts suggest that a normal family of four (two adults, two children) uses about 80 gallons of hot water per day.

Of course, your hot water use also depends on your habits and patterns: a water-frugal family of four could reduce that figure by a quarter whereas a home without a shower can significantly increase usage.

Alternatively, you can use your utility bills and community figures to estimate your hot water use. On average, a home heats about 30% of all the water it uses. Take an average of your water use figures for the winter period (when outdoor water use is at a minimum) and calculate 30% of it as hot water.

If you find that these two methods give very different answers, it's worth contacting a local renewable energy professional and asking for their advice. They may not give you an estimate based on your particular circumstances but they should be able to leverage their experience and local knowledge to guide you in the right direction.