Size Your Water Heater First, Ensure Lasting Energy Efficiency

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Riddle: How does a hot water heater not waste energy? Answer: When it’s properly sized. The water heater — or water heaters — in your greater Cincinnati home should have the capacity to easily meet your home’s high-demand-period needs yet operate efficiently without wasting energy — or water.

Need sizing for a combination water/space heating system? See your HVAC contractor about your specific situation.

How to size your water heater
Tankless units are rated by the maximum temperature rise they can efficiently achieve at a certain water-flow rate. Calculate requirements for whole-house water heating and/or remote heating, such as for a bathroom in a guest house.

  • Flow rate: Estimate how many hot water fixtures (sinks, showers, appliances) you expect to use at once, and total the flow rates in gallons per minute.
  • Temperature rise: Subtract incoming water temperature from the necessary output temperature. A rule of thumb is to assume input water is about 50 degrees. Water heated to 120 degrees is normally fine for household use.

Continuous water heaters are generally capable of a range of input temperatures. A 70-degree rise can generally flow at a rate of 5 gpm with a natural gas on-demand water heater and 2 gpm with electric heating. Lower inlet temps and flow rates may put out cooler water at distant fixtures. It’s possible to adjust the output temperature via thermostat-controlled systems.

A solar water heater’s storage capacity and collector area must efficiently handle at least 90 percent of a home’s summer hot-water requirements. Solar heating-system experts can take measurements to figure your system needs and size.

For storage tank and heat-pump heating, the first hour rating is key to determining the amount of hot water the heater can put out hourly. Select a unit with first-hour ratings that reach within 2 gallons of peak-hour needs.

Have questions about how to size your water heater? The professionals at Apollo Home Heating, Cooling and Plumbing are happy to help. Visit our website, or call us for solutions to your hot-water needs.

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"Ernie & Mike did a superb job on my new furnace and A/C installation. Despite having more than a day’s work to do, they came in and stayed until the job was done. They were organized, efficient, and protected the rest of the house well. Got both furnace and A/C installed the same day. Ernie was courteous, informative, and clearly knew his job better than anyone I’ve encountered before. The units look so good guests now get The Tour of our new system. Apollo is clearly not a fly-by-night company. I would recommend them to anyone in need of a new furnace and/or A/C."
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"The team at Apollo exceeded my expectations. As a business owner, my attention to the details and commitment to providing excellent service is high. From the sales rep. to the installation team, everyone’s performance was outstanding. For example, the installation team went to great lengths to protect our floors, placing floor runners and across the wood floors and up the stairs. They even were spot washing walls upon their departure. I highly recommend this company."
- Randy B.
"We scheduled an estimate AND a tune-up. We knew something was wrong with our furnace, but hoped we could make it through the rest of the season. Upon telling Bill what our furnace was doing, he warned us immediately what the possible outcome was going to be; a cracked heat exchanger. He watched the flames roll backward, tested carbon monoxide levels, which were so high they meter’s last reading was 5,600 before saying “high”. He immediately shut it down, tagged it, and explained that with levels that high and children in our home he wanted off right away. He continued his inspection and showed us via a camera that not only was it cracked in multiple places, but had holes all over it. He gave us a few options for repairing it; his knowledge as well as genuine concern was beneficial and refreshing. Luckily we also scheduled an estimator, Micah, to come too and we were able to get costs between repairing and replacing (with several options). We decided to replace with a much higher efficiency furnace and one sized properly to our home. Hands down, not only did they both provide us great service and knowledge, but without sounding dramatic, they may have saved our lives. This was our first time calling Apollo, but it won’t be our last."
- Sarah B.
"Apollo is an excellent company. I always receive great service. Alex A. was professional and friendly. He kept me informed during the process of checking my furnace and heat pump to make sure they were working properly. The company makes sure you are notified who is coming and when they are on the way. All my interactions with the company have been wonderful."
- Beverly S.



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