Choosing the Right Hot Water System Size

When getting a new hot water system, you have to think about the hot water system size you need for your home. Believe it or not, there are numerous hot water system sizes that make shopping for a new one somewhat challenging. Fortunately, you can follow some simple guidelines to help you choose the right hot water system size for your needs. While your individual hot water needs might differ slightly from these recommendations, they will give you a good idea of what size will work best for your home.

how to choose the right water system size

General Estimate

To really understand what size hot water system you need, you’ll want to calculate the amount of hot water your household uses during the time of day when you use the most hot water. However, if you just need a general estimate for size to start shopping around or to get a loose idea of how much it’s going to cost you to buy a new hot water system, you can use these basic numbers to find the right water heater size:

  • If there is one or two people in your household, choose a 30-40 gallon system.
  • If there are two or three people in your household, choose a 40-50 gallon system.
  • If there are three or four people in your household, choose a 50-60 gallon system.
  • If there are five or more people in your household, choose a 60-80 gallon system.

As you can see, there is some overlap in the right size hot water system when there are two or three people in your household. This is why you’ll need to more carefully consider your household’s hot water usage before actually deciding on a system and having one installed.

Hot Water Usage Habits

The larger factor in what size hot water system you should purchase is your household’s hot water usage habits. Some families of five might be perfectly fine with a 30-gallon system because they don’t use very much hot water. Maybe they’re used to taking short showers and washing their clothes in cold water. Perhaps they have very few hot water appliances in their home and are very conservative when using hot water throughout the day. A 30-gallon system might make perfect sense for them.

Conversely, a couple could need a 60-gallon hot water system because they enjoy taking long, luxurious or multiple showers and believe their clothes can’t get sanitized without being washed in scalding water. They may also run their dishwasher frequently, which also increases the usage of hot water. In their case, the smaller recommended size hot water system for one or two people wouldn’t meet their needs.

hot water guide

Calculate Your Exact Usage

As previously mentioned, the best way to determine the right size hot water system for your household is to calculate your actual hot water usage. You can do this by estimating the amount of hot water you use for various activities (10 gallons for a shower, four gallons for handwashing dishes, six gallons for using an automatic dishwasher, and seven gallons for a clothes washer) and multiply each activity by the number of times it happens during your peak hour of usage.

Conclusion

Once you’ve calculated your exact water usage, you can find the first hour rating (FHR) for a hot water system that matches your peak hour usage. This will ensure you have the right amount of hot water for even you heaviest usage times.

author avatar
Salman Zafar
Salman Zafar is the CEO of BioEnergy Consult, and an international consultant, advisor and trainer with expertise in waste management, biomass energy, waste-to-energy, environment protection and resource conservation. His geographical areas of focus include Asia, Africa and the Middle East. Salman has successfully accomplished a wide range of projects in the areas of biogas technology, biomass energy, waste-to-energy, recycling and waste management. Salman has participated in numerous national and international conferences all over the world. He is a prolific environmental journalist, and has authored more than 300 articles in reputed journals, magazines and websites. In addition, he is proactively engaged in creating mass awareness on renewable energy, waste management and environmental sustainability through his blogs and portals. Salman can be reached at salman@bioenergyconsult.com or salman@cleantechloops.com.

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