It depends where in the US you live because that affects the inlet water temperature. Power measured in kW , however, is absolute. All in all, you also have to take into example some financial calculations.
You are recommended to check if a tankless water heater is really worth it we made some calculations here. The second one is based on the number of people living and using hot water in your household. For example, how large a tankless water heater does a family of 5 need. Here is how this situation goes: You currently have a 30, 40, 50, or even gallon water heater and want to replace it with a tankless water heater.
During an average minute shower, for example, you spend about 10 gallons of hot water. If 3 people have a shower, you run a faucet or two, a dishwasher, and so on, you can quickly spend all those 50 gallons.
However, the case with the tankless water heater is different. Be mindful that this is only a rough estimate. The smart thing to do is buy a tankless heater that is a bit more powerful than the estimated needs.
Better be safe than sorry. If 5 people live in a single household, they can use several faucets or showers simultaneously.
When picking the size of a tankless water heater, we have to take this into account. A household hot water consumer that requires hot water fastest is a shower.
In short, a family of 5 would need a 10 GPM gas tankless heater or 27 kW electric tankless heater if you live in the northern part of the USA, where the input water has a lower temperature. So, for a family of 5 in the southern part of the USA, that would mean a 7 GPM gas tankless heater or an 18 kW tankless heater should be more than enough to satisfy all hot water needs.
Do be aware that, especially with bigger units, you can save a lot on hot water with tankless water heater circulation pumps. These pumps are quite useful if you want hot water from a faucet or shower quickly. In most cases, you need only 1 tankless heater for an entire house. The big tankless heater takes care of the most hot water needs. On occasions when we need a tremendous amount of hot water, the electric tankless water heater is switched on to help out.
Another example is if you have one unit for one part of the house and another unit for the other part of the house. In this case, the piping for both units is separate.
What size would a home with 1 adult, no dishwasher and use only cold water in washer need? Just shower and bath. Hello Laurie, those are pretty much the minimum hot water requirements. You can check out this and other tankless electric heaters here. My house has two 50 gallon tanks one on either side of our upstairs in closets. Do I need to get two tankless heaters because of the lines or just one?
What sizes would I need? So, the easiest solution would be to buy two 9 GPM units and install them on the existing lines. The best ones are Rinnai gas tankless heaters, you can check them here. Hi there. I live in South Jersey where it looks like the ground water temp is 50F, according to the map.
We use the hot water for showers, dishes and the occasional bath. We do not yet own a washer machine but when we do we will occasionally use hot water in that as well. It will be a small machine, maybe 3cf. You can check out a range of electric tankless heaters hot water here. We have 4 kids, oldest beginning to go into teenage years.
So HUGE water needs for a family of 6. We have a traditional water tank now and run out of water if we have people showering around the same time.
We are in a very cold climate. Hello Marie, your assumptions are correct. With such a large family, the hot water needs are quite high. We live in Central Florida and are building a two-story, s. We will have 4 showers in the house but only 3 of them will be used on a daily basis. Right now, the plan is to have a Rinnai RL94E tankless gas water heater.
Recently, we were told by one of the vendors that we may need two. Is that really necessary? Seems like an unnecessary expense. Hello there, the Rinnai RL94E has a maximum how water flow of 9. In Boston or New York, maybe, but 9. I think having that configuration should be more than sufficient. I have no interest in maintaining 2 water heaters! What size of electric water heater do I need for 2 persons, washing machine, dishwasher and kitchen sink. I live in the Caribbean. You can check the Stiebel unit and other smaller tankless electric water heaters here.
Hello Tad, those are quite high hot water needs. You can check out high kW electric tankless heaters here , Stiebel Eltron does offer 36 kW units, for example. Hi, I live in the norther zone of illinois. We have 5 people living in a square foot home. Would be no more than a shower, dishwasher, and efficient washing machine at same time.
Do you plan to run two showers at the same time or run several sinks at the same time? It is recommended that you use 1. If you are running two different showers at the same time, you will need at least 5 gallons of water from your tankless water heater. If you need to run both your washing machine and shower at the same time, you will use around 4. You will want to make sure that you size your heater accordingly. Determining your usage rates will help you to pick the right tankless water heater for your needs.
If you need to produce a larger water temperature rise per GPM, you may want to consider getting a gas tankless hot water here. These gas hot water heaters are able to increase temperatures quickly. They will be able to tell you the water heater size that you need and show you the best options available.
They can sit down and go over your usage rates to determine whether or not you would be better off getting an electric tankless hot water heater or gas one. When you hire a professional plumbing company, you will not have to worry about having to install the hot water heater or having to ensure that you have the right size. Water heater installation can be difficult and dangerous, so it is always a great idea to leave it to the professionals. This was way back in , good to see the US catching up.
I live in a square foot house with a need for hot water for a shower no bathtub , bathroom and kitchen sink and clothes washer.
I am thinking I need only 5 gpm, any suggestions? It should be noted that many modern day Dish washers can actually heat their own water electronically. Better late than never on my reply. Residential dishwashers can only heat the water an additional degrees. They need hot water delivered to them or may throw error codes and not clean your dishes. I have a shower and tub, dishwasher 2 sinks.
I live in a small house. OH, and how difficult are they to DIY install?? What size tankless heater do i need for a 3 bedroom 2 bath house. I have 2 small children and we run the washer daily. We want to replace old water heater with gas tankless. Three bathrooms, on on each level all with showers. Dishwasher and washer on second floor, which is our main floor. We live in mountain area of east coast. Have any idea the size of one that would run our whole house. Can I use a v electric tankless water heater for a shampoo bowl area for a salon and how many 4gpm would I need.
Can I use a v electric tankless water heater for a shampoo bowl area for a salon and how many gpm would I need. I have a heart shape jacuzzi tub and 3 showers in the home never enough hot to fill tube can i fill the tub if someone is showering and wash is being done what size unit do i need or how about 2 showers and wash.
Dear Jeff, I have a nail salon with 9 pedicure chairs. I currently have gal AO Smith tank water heater. In the busy days, I ran out of hot water. I though to install an additional water heater and not sure that should I purchase another tank water heater or tankless one, and if tankless, what will be the right size?
Thank you and best regards. Hi, we presently have a gas heater in our holiday home, but the municipal water pressure is very variable. We also seem to have a bit of scale build-up in the warm water pipes any advice on how to get rid of that would be much appreciated. Unless you shower early in the morning or late at night, chances are slim that you will get any hot water, since the gas heater is triggered by a sufficient flow of water.
So cold showers and hot tempers all around. Would a tankless water heater be similarly affected by the lack of water pressure? Can we install the tankless heater in the same spot where the gas heater is presently i. If so, it can heat the bathroom and kitchen taps. Thanks for the help, Vilya. We live in penna what would you suggest as size for gas hot water tankless unit. You never do answer the actual question of what size water heater is required for demand. You talk about flow rate but not kW.
So running a shower and dishwasher at the same time would require what size heater as far as kW? So, I have a tankless gas water heater — it is very problematic! The temp is turned up as high as it will go, and still, sometimes water will not get hot or even warm and sometimes it will!
However, it seldom stays warm thru the entire shower! Sporadic heating! The unit is approaching 20yrs old — time to replace it??? Or might it be repaired? It is a 3 story bldg with a beauty salon on the 1st floor and 4 other people on the 2nd and 3rd floor.
Note: even when the salon is closed, there are still issues! If the tankless heat exchanger has not be flushed for a while, it may be scaled up too much for proper heat transfer. If this tankless is providing hot water for all that you list, then it is likely undersized for all the potential users.
With many possible fixtures that could run at the same time, you usually need more storage, even if the tankless heats that particular tank. Duane, Master Plumber. Hello, your article notes that inflow water should not be preheated.
With the new smart technologies, is this still the case? I have a small restaurant, no dishwasher, 3 compartment pot sink, 2 hand washing stations and 2 bathroom, what size tankless water heater do I need.
Example: 3 C Sink 2. To measure your Flow Rate take a 1 gallon jug to each hot water dispenser time how long it takes to fill the 1 gallon jug. The problem is there is only one unit for a 5 bedroom 3 and a half bath… and it is located on the farthest wall in the garage, one master bath upstairs, being the farthest away, takes around 5 minutes to get hot water to the shower, and the kitchen is not much closer to the unit. Then there is a second master bath downstairs, below the other master….
I would like to know the answer to this question also. I thought about installing a second unit outside near master bathroom and kitchen area. You might consider a circulation pump to keep the lines hot during a certain time period you are around. You can install a crossover valve under the farthest sink for example. I have a sq ft home. The Shower, kitchen sink, and dishwasher are all within 10 feet of each other on 1 wall dishwasher back to back with the shower. In areas with hard water, a vinegar flush every hours keeps mineral buildup—scale—from clogging the heat exchanger.
That minute task can be done by either a pro or a homeowner. Gas-burning tankless water heaters should operate for 20 years or more, two or three times longer than tank-type heaters. Tankless electric units have shorter life spans, on the order of 7 to 10 years. Plumbing supply stores, big-box stores, and online retailers all carry these heaters. Or order one through your plumber. Newer tank-type water heaters have grown bigger as federal regulations now require thicker insulation to reduce standby heat loss.
So they may not be able to fit into spaces where an old heater of the same capacity could go. Tankless gas heaters are about the size of a suitcase and hang on the wall.
Owners of vacation homes know well how long it takes to drain a water-heater tank before closing up a house for the winter. With a compressor, you can drain a tankless heater in a few seconds; then you just unplug it. But because these tankless gas units last longer, the savings kicks in after six years, about when many tanks are nearing their demise. Tankless technology is constantly improving. Here are some of the latest refinements:.
Tankless units take about 15 seconds to bring water up to temperature, but you still have to wait for that hot water to arrive at your shower head or faucet, just as you do with a tank-type heater. When the distance between heater and fixture exceeds 50 feet, look for units with a built-in recirculation pump, which saves water and reduces waiting time.
The pump, which can be turned on by a timer, a push button, a motion sensor, a smart speaker, or a smartphone above , pushes the cold water in the pipes back through the heater. After about a minute, the pump shuts off and you get hot water seconds after opening the tap.
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