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What Size Water Heater Do You Need

Save Money & Purchase Energy Star Water Heaters


As a general rule of thumb, professionals say for most homes a properly sized water heater will meet your household’s hot water needs while operating more efficiently. Now if you have a large family with kids active in sports that require additional showering, laundry, or say you have a hot tub, then your mileage may vary.

Proper evaluation is a must and that’s where Action Plumbing Heating and Air Conditioning & Electric comes in. We can help you determine what you must have to exceed demand. And remember to ask about the Energy Star Water Heater Products that can start saving you money the first day. See More Here

For long-term investments, consider purchasing an energy-efficient water heater. Whether you’re looking at tankless water heaters or considering solar, our new Energy Saver 101 water heater infographic lays out the different types of water heaters on the market and will help you figure out how to select the best option for your home.

Proper water heater installation is a very detailed and tedious process and should not be undertaken as a do-it-yourself project. Action Plumbing Heating Air Conditioning & Electric has over 27 years of experience in water heater installation, repair and maintenance. Put our good reputation to work for you. Whether you need replacement or maintenance checks, we are confident you will be satisfied with our work.

When you call us here at Action, a professional plumber can discuss all the options, and ask all the right questions so you know about what demand is required.. For a commercial or institutional facility like a school, hotel, kitchen or office complex please consider there are many more factors that may determine the type of water heating solution you need in a given situation. For over 27 years Action Plumbing Heating Air Conditioning Heating & Electrical has provided quality water heaters for home, business, commercial, and institutional clients in the Madison and Sun Prairie area.

Action Plumbing Heating Air Conditioning Heating & Electrical, your favorite Madison Plumber, is here to make sure that you have all the information you need to accurately determine what is the right size water heater for your home or business, institution or commercial facility. We also ask the questions that can help save you money by purchasing ENERGY STAR Qualified Water Heaters as your first consideration.

Here in the Madison Sun Prairie market, most homes use traditional style water heaters. However new construction in homes, business, and commercial facilities require new sizing combinations, water and space heating systems — including some heat pump systems, and indirect water heaters all matter. Remember that here at Action, we will help you by setting an appointment to consult a qualified contractor keeping specifications in mind.

Information Discussion Points:

  • Replacement, installation and maintenance of traditional style water heaters
  • Solar water heating system
  • Storage and heat pump (with tank) water heaters
  • Tankless or demand-type water heaters

Sizing Tankless & Demand-Type Water Heaters

Business and Commercial Water heaters are usually rated by the maximum temperature rise possible at a given flow rate. When you need to size a demand water heater, flow rate is must be determined for proper installation. Next the temperature rise you will need for its application. That information would include the whole house, office, or commercial location like the bathroom in the home. Let’s begin with the number of hot water devices you expect to use at any one time. Now add up their flow rates (gallons per minute). The result will be the desired flow rate you’ll want for the demand water heater. This is a process that includes hot water faucet flow rates, shower head flow rates, and flow rates through the water heater. Temperature rise and output temperatures are considered, and dish washers, washing machines and kitchen instant hot water faucets can all be considered as well. Space available, location from water source, and future growth can all also be considerations in the plan to provide what you need.

Sizing a Solar Water Heating System For Home Or Business

Many clients have asked about Solar Water Heating Systems. The proper sizing of your solar water heating system basically involves several things. First to determine the total collector area and the storage volume you’ll need to meet 90%–100% of your household’s hot water needs during the summer is the place to begin. Most typical Solar systems worksheets and computer programs to help determine system requirements and collector sizing. If you need specifics about your system, or you are interested in finding out more, just give Action Plumbing a call and we can discuss your options.

Collector Area – As another point of information, Action Plumbing can follow a guideline of around 20 square feet (2 square meters) of collector area for each of the first two family members. Additions need to be made for more people. By adding 8 square feet (0.7 square meters) if you live in the U.S. Sun Belt area or 12–14 square feet if you live in the northern United States, will usually be recommended.

Storage Volume – Consideration for total storage volume is another item you want to understand. A small (50- to 60-gallon) storage tank is usually sufficient for one to two or three people. A medium (80-gallon) storage tank works well for three to four people. A large tank is appropriate for four to six people. Remember there may be extenuating circumstances that could affect storage.

In a very active system, the size of the solar storage tank needs to increase with the size of the collector. This is typically around 1.5 gallons per square foot of collector. Using this guideline, prevention of the system from overheating takes place when the demand for hot water is low. In very warm, sunny climates, some experts suggest that the ratio should be increased to as much as 2 gallons of storage to 1 square foot of collector area. Hot summers in Texas may need an adjustment, but each system may vary, so let our qualified staff here at Atlas examine the correct options here, and make recommendations.

Additional Considerations – Additional calculations involved in sizing your solar water heating system may include evaluating your building site’s solar resource and determining the proper orientation and tilt of the solar collector. Each system may vary, along with current City Codes in your area. Atlas can visit the manufacturer recommendations on the solar water heaters specs page for more on these calculations.

Sizing Storage and Heat Pump (with Tank) Water Heaters

Most clients here in Madison already know the proper size water heater you need for your home. If you are already a client, or if you have increased your family there may be additional items for discussion. Our staff will include a heat pump water heater with a tank use that has the water heater’s first hour rating. The first hour rating is the number of gallons of hot water the heater can supply per hour (starting with a tank full of hot water). Be mindful this totally depends on the tank capacity, source of heat (burner or element), and the size of the burner or element. All three must be considered.

The EnergyGuide label provided on the tank by the manufacturer lists the first hour rating in the top left corner as “Capacity (first hour rating).” The Federal Trade Commission requires that this EnergyGuide label must be on all new conventional storage water heaters but not on heat pump water heaters. Product literature from a manufacturer may also provide the first hour rating. Look for water heater models with a first hour rating that matches within 1 or 2 gallons of your peak hour demand — the daily peak 1-hour hot water demand for your home.

How To Estimate Your Peak Hour Demand:

Several factors play a part here. First, determine what time of day (morning, noon, evening) you use the most hot water in your home. For most it’s in the morning getting ready for work or school for the kids. Remember to keep in mind total numbers of people that occupy the home every day. If you prefer to evaluate this information before we come out, here is a worksheet guideline that may be helpful. A guideline worksheet can estimate your maximum usage of hot water during this one hour of the day—this is your peak hour demand. Note: usually this worksheet does not estimate total daily hot water usage. Find the link here: http://energy.gov

The worksheet example shows a total peak hour demand of 36 gallons. Therefore, this household would need a water heater model with a first hour rating of 34 to 38 gallons. Worksheet for Estimating Peak Hour Demand/First Hour Rating *

Use: Average gallons of hot water per usage Times used during 1 hour Equals Gallons used in 1 hour

  • Shower 10 × =
  • Shaving (.05 gallon per minute) 2 × =
  • Hand dishwashing or food prep (2 gallons per minute) 4 × =
  • Automatic dishwasher 6 × =
  • Clothes washer 7 × = Total Peak Hour Demand =


  • 3 showers 10 × 3 = 30
  • 1 shave 2 × 1 = 2
  • 1 hand dishwashing 4 × 1 = 4
  • Peak Hour Demand = 36

Adapted from information from the Federal Energy Management Program Energy Cost Calculator see the link above *The above worksheet is based on standard usage with no water conservation measures.

Action Plumbing Heating Air Conditioning & Electric has a reputation of solving water heater challenges quickly and efficiently, and we treat our customers with the respect they deserve. 100% customer satisfaction with our work is the key to earning this respect. Action Plumbing has professional technicians for all types of water heater repairs maintenance and installation. It is our belief that by understanding water heater maintenance and upkeep, we can help you maintain and extend the life of your water heater.

Check it out today, call us here at Action Plumbing, Heating, Air Conditioning and Electric, Inc. Your Madison and Sun Prarie Water Heater specialist Sun Prairie, WI: (608) 837-3638 to set up an appointment to speak with our qualified staff about your commercial location for a new Water Heater.

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