Water heaters are usually out of sight, but they spring to mind the second your shower goes cold. When it’s time to replace, upgrade, or buy your first water heater, start with what you know. Carefully evaluating your water use and hot water demands may reveal better options and help you avoid surprise ice baths in the future. This article will cover how to estimate your demand and apply that knowledge to the most popular types of water heaters.
Determining Your Demand
While every household uses water differently, here are some general guidelines to help you estimate your household’s demand:
- An eight-minute shower uses about 17 gallons of water.
- Dishwashers range widely, requiring 2-10 gallons per cycle depending on make, year, and efficiency. Look up your specific model for an accurate estimate.
- Washing machines are as varied as dishwashers, averaging 20-40 gallons per cycle, so look up the details of your current equipment.
- Miscellaneous things like washing your hands will add to your demand, so round up when you calculate.
If you’re replacing an existing water heater with a similar type, use your experience as a starting point. A water heater that meets demand should provide enough hot water to accomplish various tasks during the busiest hour of your household’s day. This likely includes multiple showers and other grooming activities in addition to dishwashing or laundry. If you’re satisfied with the hot water output of your current system, you already have a good starting estimate, even if you plan to try a different type of heater.
On the other hand, showers that go cold during peak demand hours are one of the biggest signs your water heater is insufficient. Note which activities you can perform before you lose hot water. Compare this to a list of your actual hot water demands. For instance, if you have three people who need to shower in the morning and the second shower turns cold halfway through, you’ll likely need a water heater considerably bigger or more powerful than your current system.
Storage Water Heaters
To find your ideal storage water heater, evaluate its capacity and first hour rating (FHR). Capacity refers to the water heater’s reservoir. The reservoir is a tank that heats and holds water at a certain temperature. As the hot water is used, cold water flows into the reservoir, and the system heats it. The size of the reservoir determines how much hot water it can supply at a given time. These typically range between 20-80 gallons.
The FHR is an official rating judging how much hot water a fully heated water heater can put out in a single hour. It’s measured in gallons, and the lowest required rating for Energy Star certification is 45 for electric systems and 51 for gas-fired options. If you know your demand, you can estimate if a specific unit will meet your needs by comparing your maximum demand time (i.e. mornings with multiple showers, dishes, etc.) with a unit’s FHR.
Tankless Water Heaters
Tankless or demand-type water heaters don’t store hot water, making them more energy efficient. It also means homeowners have to measure their capacity differently. Flow rate and temperature differentials determine how well a tankless system will perform in an individual residence, and every home has different flow rates and temperature rise requirements.
Flow rate determines how much water leaves specific taps or faucets in a set timeframe. To figure out if a tankless water heater can meet demand, count how many outputs (such as showers and sinks) you plan to use at the same time. Your fixtures may already have flow rates listed. If they don’t, you can measure flow rate by running the outlet for a minute, collecting all the water it expels, and measuring the volume of water you’ve collected during the timed minute.
You will also need to check for temperature rise. To do this, measure water temperature before and after it passes through your water heater. You can also estimate by checking the temperature of cold water leaving a regular faucet and subtracting that number from your desired temperature. The result is your desired temperature rise.
When to Consult an Expert
An expert makes replacing or installing a home water heater easier. Benjamin Franklin Plumbing’s team can help you analyze variables, determine flow rates, and anticipate demand with the latest solutions. Whether you want partners to take the first steps with you or a professional to put the finishing touch on your DIY project, we are ready to serve.