What Size Tankless Water Heater Do I Need To Replace A 50 Gallon Water Heater
Written by: Gene Fitzgerald // Last Updated:
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Tankless water heaters provide endless hot water on need. Furthermore, they can reduce your utility bills by more than 30 percentage due to the elimination of standby free energy losses, they are about the size of a suitcase and therefore space-saving, and they terminal upwards to xx+ years which is almost twice as long as what you become out of a regular tank-based unit.
Yet, tankless water heaters are limited by how much water they tin can heat at any given time. Choose besides minor of a system and it won't take the capacity to provide enough hot water to meet your household needs. Go besides big and you volition overpay. This is why proper sizing is key – earlier making a purchase.
This buying guide will walk you through the process of sizing a tankless h2o heater and also shed light on other aspects that you have to consider when shopping.
Contents
- How to size a tankless h2o heater
- Step i: Flow rate – how many gpm for a tankless h2o heater
- Step 2: Temperature rise
- Step 3: Putting it all together
- Video
- Size chart
- Example size chart
- Tankless water heater sizing computer
- Oftentimes asked questions
How to Size a Tankless Water Heater
Only put, tankless a.m.a. on-demand water heaters are rated past their maximum output h2o menstruation rate at a specific temperature rise.
So, in guild to size a tankless water heater you have to consider 2 things:
- How many gpm (gallons per minute) of hot h2o you lot need at times of summit consumption. Remember, tankless water heaters don't store whatsoever water merely heat it as it flows.
- The required temperature rising which is determined past feed h2o temperature and output h2o temp settings.
What if you undersize?
Bad idea! If the required hot water need surpasses the possible maximum, fifty-fifty if merely temporary, nearly water heaters will throttle the flow automatically. This ways less hot water at every outlet and therefore a temperature and/or pressure drop.
In addition, a tankless water heater that runs at full speed all the time is more likely to suspension downwards prematurely.
What if you get too big?
Oversizing is not that big of a deal. The simply issue is unnecessary upfront price.
Step i: Menstruum Charge per unit – How Many GPM for a Tankless Water Heater
Allow's commencement by figuring out your peak hot water demand. You tin use the nautical chart below for this. It lists the standard flow rates of different types of water outlets sold in the U.Due south. Of course, you could besides look upward your specific fixtures etc. online or check their production manuals.
But determine which devices y'all desire to exist able to run simultaneously and how many of them. Then add up their flow rates.
For example, if you need 1 shower and one kitchen faucet running at the same time your required maximum water flow is:
2.5 gpm + 2.2 gpm = iv.7 gpm
For WaterSense-certified products, the required flow rate is:
two.0 gpm + 1.v gpm = 3.5 gpm
Pretty elementary! But before you lot get started, here are a few more than tips:
- By planning for maximum demand at summit hours like in the morning you can ensure that y'all always have hot water at the fix no matter what. To a higher place that, a tankless water heater that does not have to run at total capacity all the time is probable to last longer. At the same time, a fiddling planning will allow you to reduce your elevation demand significantly. This includes taking turns when showering, letting the dishwasher do its thing while everyone is out of the house, and preparing your food before or afterwards the showers are finished.
- Apparently, you lot have to take into account not but the number of bathrooms in your home, just also how many people are living under ane roof. ii people tin merely apply 2 showers at the same fourth dimension, fifty-fifty in a 5-bathroom mansion.
- Ask yourself: Volition the water heater serve your entire home or simply parts of it?
- The catamenia rates listed below indicate total water output, and then hot water PLUS cold water. In other words, showering with a ii.five gpm shower caput does not hateful that all of the water will be hot. It is more likely that you lot mix in some common cold to get the desired temperature. Thus, the bodily hot water demand is somewhat lower.
- To reduce flow rates you could install low-menstruum aerators or fixtures.
| Water Outlet | Standard Flow Rate |
|---|---|
| Paw washing sink | 0.5 – 1.5 gpm |
| Shower caput | ii.v (two.0*) gpm |
| Bathroom faucet | ii.2 (1.5*) gpm |
| Bathtub faucet | 3.0 – 4.0 gpm |
| Kitchen faucet | ii.2 gpm |
| Washing machine | 23+ gallons per load, gpm hard to determine |
| Dishwasher | 6 gallons per load, gpm hard to determine |
*WaterSense certified products
Please notation: Older fixtures are likely to have higher flow rates.
As you tin run into, we did not include menstruation rates for washing machines and dishwashers. This is because we plant it very difficult to get reliable data on this. Some sources say 2 to iii gpm, others 1.five.
What you could do is run each apparatus separately and monitor your water meter and measure out time. This will give you a rough thought of how much flow is needed.
Speaking of measuring, for a more scientific approach to determining your peak water flow y'all can take a 1-gallon bucket and track how long it takes your shower caput, kitchen faucet, bathroom taps, etc. to fill it. Then use the following formula to calculate the flow rate for each outlet:
Flow rate = 60 / Seconds required to make full saucepan
If you don't want to waste a full gallon per outlet, just fill a quart and use this formula instead:
Period charge per unit = 15 / Seconds required to fill ¼ bucket
Step two: Temperature Ascent
The next footstep is to determine your required temperature rise. Here all you have to do is subtract the temperature of your feed h2o from the desired output h2o temp.
Required temp rise = Output h2o temp – Feed water temp
How can you find out what temperature your feed water has? You have two options:
- Measure with a thermometer
- Use our crawly U.S. boilerplate groundwater temperature map
Please annotation: These are average temperature estimates. Real temperatures vary with flavour and weather.
As y'all can see, where you live in the country plays a huge role as far as average groundwater temperature is concerned. In warmer climates in the southward, the temperature will naturally be higher, upward to 77 °F in southern Florida. Whereas in Alaska, parts of N Dakota, Minnesota, Wisconsin and other states in far northern regions the groundwater temp can exist as low every bit 37 °F.
At present, this makes a big difference every bit to how much a tankless water heater has to work to bring water upwards to the desired temperature. Let's say you live in Michigan with 40 °F average feed water temperature. And you aim at 110 °F output temp. The required temperature rise would exist
110 °F – 40 °F = 70 °F
A water heater installed in a home in Texas with 70 °F inlet water temp has to warm up the water by as piffling equally
110 °F – lxx °F = twoscore °F
Past the way, 105 to 115 °F output h2o temp is considered ideal for everyday household utilise. 105 °F is considered the upper end of the temperature range most comfy for showering. At your kitchen sink you want something around 110 °F.
Stride iii: Putting It All Together
Okay, you lot know your hot h2o demand at peak hours as well every bit the required temperature ascension.
The last footstep is to become out and look for a tankless water heater that meets these requirements. Basically all manufacturers provide sizing charts with their products that specify maximum flow rates at a given temperature rise or vice versa. Some manufactures likewise list period rates for different input/output water temps.
You desire to cull a unit size that either meets or exceeds your elevation hot water demand.
Be aware, though, that manufacturers similar to promote their products using all-time-case scenarios, so accept the information with a grain of table salt. Some companies tend to exaggerate with what their systems tin do…
Ready for the next step? Cheque our electric tankless water heater reviews to discover a arrangement that perfectly fits your needs!
Video
Adopt video? Check this out:
Size Chart
Check out a few size charts and y'all volition speedily notice that gas or electric makes a huge difference. By and large speaking, tankless gas water heaters are more powerful, meaning that they can produce higher gpm than electric units at the same temperature rise.
For example:
If your required temperature ascent is 70 °F, a large tankless gas water heater can supply 5.0 – v.5 gallons per minute. The largest electric unit (36 kW) maxes out at fiddling more than 3.0 gpm.
Instance Size Chart
For reference, this is what a tankless water heater sizing nautical chart looks like:
This item heater can provide 6.6 gpm at a 50 °F temperature ascension and 4.8 gpm at 70 °F.
Popular Tankless H2o Heaters
These are some real-life examples of pop tankless water heaters:
(Mobile Hint: Swipe to Ringlet)
| Model | Fuel Type, Power | Temp Rise | Max GPM | # of Bathrooms |
|---|---|---|---|---|
| Rinnai V75iN | Natural gas, 180,000 BTU | 70 °F | 4.3 gpm | 1 – 2 bathrooms |
| l °F | half dozen.0 gpm | 2 – 3 bathrooms | ||
| Rinnai RU199iP | Propane, 199,000 BTU | lxx °F | five.5 gpm | 2 bathrooms |
| l °F | 7.6 gpm | 3 bathrooms | ||
| Stiebel Eltron Tempra 36 Plus | Electric, 36 kW | 70 °F | iii.five gpm | 1 bathroom |
| 50 °F | 4.75 gpm | 1 – 2 bathrooms | ||
| Rheem RTEX-xviii | Electric, 18 kW | 65 °F | ii.0 gpm | ane bathroom |
| 55 °F | 2.0 gpm | i bathroom | ||
| EcoSmart ECO eleven | Electric, 11 kW | 68 °F | 1.1 gpm | ane bathroom |
| 48 °F | 1.56 gpm | 1 bath |
Frequently Asked Questions (FAQ)
1. What Size Tankless Water Heater Exercise I Need for a Family of 5?
This is near impossible to tell. It depends on how many bathrooms and h2o using appliances you have, and the required temperature rising. Become through steps 1 to three in this sizing guide or use our tankless water heater sizing figurer and you lot volition get an reply to your question – guaranteed!
two. What Size Tankless Water Heater Do I Need to Replace a 50-Gallon Water Heater?
Again, this is simply not enough information to give a reliable answer. It depends on how many bathrooms and water using appliances y'all have, and the required temperature ascension. We recommend y'all go through steps 1 to 3 in this sizing guide or utilise our sizing computer!
3. How Many Tankless Water Heaters Practise Yous Need?
How many tankless water heaters y'all demand depends on your peak hot water demand and required temperature rise (bank check sizing guide above).
In general, one tankless gas water heater should be enough to supply a mid-sized family/domicile. Electric tankless water heaters are perfect for smaller families and apartments.
In case of very high demand, consider installing two or more heaters, either at the point of use and so they work separately from one another or in one primal spot to work in tandem operating equally a unmarried unit.
Furthermore, although more than expensive upfront, calculation two smaller units in series can sometimes make more sense than installing one large one.
If you have whatsoever thoughts or questions well-nigh how to size a tankless water heater please don't hesitate to leave a annotate below!
What Size Tankless Water Heater Do I Need To Replace A 50 Gallon Water Heater,
Source: https://www.best-osmosis-systems.com/tankless-water-heater-sizing/
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