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Gas Tankless Water Heaters

Takagi T-KJr2-IN
Takagi T-KJr2-OS
Takagi T-K4-IN
Takagi T-K4-OS
Takagi T-H3M-IN

Rinnai v65i
Rinnai RL75i
Rinnai RL94i


Electric Tankless Water Heaters
Bosch 5000 WH17 WH27
Bosch 3000 (POU)
Stiebel Eltron


Electric Mini-Tank Water Heater
Bosch ES2.5
Bosch ES4
Bosch ES8


Oil Tankless Water Heaters
Toyotomi OM-122DW
Toyotomi OM-128-HH


RV and Boat Water Heaters
RV 500
Boat ShowerMate


Water Heater Venting

3" Z Flex Venting
4" Z Flex Venting


Water Heater Accessories

Webstones Valves
Water Connections
Whitlam Descaler Solution


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Tankless Water Heaters - what size do you need?
This page will give you a quick-view look at all our Tankless Gas Water Heaters
and electric water heaters.   What size for your needs?
For more detailed information - please review each hot water heater's detailed information pages and on-line manuals.


  Sort by: All Tankless Water Heaters   Electric Tankless Water Heaters   Gas Tankless Water Heaters


One major use
A single Standard use is considered to be 2.5 gallons per minute (GPM) click for more info

  • Bosch 520 PN - Standing Pilot - Gravity Vent
  • Bosch 520 HN - Hydron Spark Ignition - Gravity Vent
  • Takagi T-KJr2-IN - Electronic Ignition - Optional Direct Vent - Horizontal or Vertical Power Vented
  • Rinnai V65i - Electronic Ignition - Direct Vent - Horizontal or Vertical Power Vented
Bosch 520 HN gas tankless water heaters will give you a max output of 4 GPM and has a Hydro Spark Ignition. This water heater with a 50-degree water input and a 55-degree temperature rise will give you 3.3 gpm. This is enough for a standard shower (2.5 gpm) and maybe a small sink at the same time. More info on Bosch 520 HN Series Tankless Water Heaters ... click here

Bosch 520 PN Gas tankless water heaters will give you a max output of 4 GPM and has a Standing Pilot. This water heater with a 50-degree water input and a 55-degree temperature rise will give you 3.3 gpm. This is enough for a standard shower (2.5 gpm) and maybe a small sink at the same time. More info on Bosch 520 PN Series Tankless Water Heaters ... click here

Takagi T-KJr2-IN tankless water heater will give you about 4.3 GPM with 50-degree water input and a 55-degree temperature rise. This is enough for one standard shower (2.5 gpm) and a small sink at the same time. The Takagi T-KJr can also be used for heating applications up to 167 ° F.
More info on the Takagi Tankless Water Heater T-KJr2-IN ... click here

Rinnai V65i Gas tankless water heater will give you about 4.6 GPM with 50-degree water input and a 55-degree temperature rise. This is enough for one standard shower (2.5 gpm) and a small sink at the same time.
More info on the Rinnai Tankless Water Heater Rinnai V65i ... click here


Two major uses
A single standard use is considered to be 2.5 gallons per minute (GPM) click for more info

  • Takagi T-K4-IN - Electronic Ignition - Horizontal or Vertical Power Vented - Optional Direct Vent
  • Takagi T-K4-OS - Electronic Ignition - Outdoor Installation
  • Rinnai Rl75i - Electronic Ignition - Direct Vent - Horizontal or Vertical Power Vented
  • Rinnai RL94i - Electronic Ignition - Direct Vent - Horizontal or Vertical Power Vented


Takagi T-K4 Tankless Hot Water Heater will give you a max output of 8.0 GPM. A 50-degree water input and a 55-degree temperature rise will give you about 5.7 GPM. This is enough for two standard showers (2.5 gpm each). The Takagi T-K4-IN can also be used for heating applications up to 167 ° F.
More info on the Takagi TK4-IN Tankless Water Heater ... click here

Takagi T-K4-OS Outdoor Tankless Hot Water Heater will give you a max output of 8.0 GPM. A 50-degree water input and a 55-degree temperature rise will give you about 5.7 GPM. This is enough for two standard showers (2.5 gpm each). For Outdoor Installation Only in Moderate Temperature Climates
More info on the Takagi TK4-OS Tankless Water Heater ... click here

Rinnai Rl75i Gas Tankless Hot Water Heater will give you a max output of 7.5 GPM. A 50-degree water input and a 55-degree temperature rise will give you about 5.6 GPM. This is enough for two standard showers (2.5 gpm each). For Indoor Installation Only
More info on the Rinnai Rl75 Tankless Water Heater ... click here

Rinnai Rl94i Gas Tankless Hot Water Heater will give you a max output of 9.4 GPM. A 50-degree water input and a 55-degree temperature rise will give you about 5.7 GPM. This is enough for two standard showers (2.5 gpm each). For Indoor Installation Only
More info on the Rinnai Rl94i Tankless Water Heater ... click here




Three major uses or more
A single standard use is considered to be 2.5 gallons per minute (GPM) click for more info

  • Any of the Takagi Water heaters with used in conjuction with a storage tank


Takagi T-K4 Tankless Hot Water Heater will give you a max output of 8.0 GPM. A 50-degree water input and a 55-degree temperature rise will give you about 5.7 GPM. This is enough for two standard showers (2.5 gpm each). The Takagi T-K4-IN can also be used for heating applications up to 167 ° F.
More info on the Takagi TK4-IN Tankless Water Heater ... click here

Takagi T-KJr2-IN tankless water heater will give you about 4.3 GPM with 50-degree water input and a 55-degree temperature rise. This is enough for one standard shower (2.5 gpm) and a small sink at the same time. The Takagi T-KJr can also be used for heating applications up to 167 ° F.
More info on the Takagi Tankless Water Heater T-KJr2-IN ... click here


Electric Tankless Water Heaters

One major use
A single Standard use is considered to be 2.5 gallons per minute (GPM)) click for more info

  • Bosch 5000 WH17 - Electric Tankless Water Heater
  • Bosch 5000 WH27 - Electric Tankless Water Heater
  • Stiebel Eltron Tempra 20 - Electric Tankless Water Heater
  • Stiebel Eltron Tempra 24 - Electric Tankless Water Heater
  • Stiebel Eltron Tempra 29 - Electric Tankless Water Heater
  • Stiebel Eltron Tempra 36 - Electric Tankless Water Heater

Bosch 5000 WH17 Electric Tankless Water Heater with a 50-degree water input and a 55-degree temperature rise will give you about 2.4 gpm. This is enough for a standard shower (2.5 gpm) where ground water is warmer than 55 degrees year-round. (80 amps - requires min 150 amp service) More info on Bosch 5000 WH17 Electric Tankless Water Heaters ... click here

Bosch 5000 WH27 Electric Tankless Water Heater with a 50-degree water input and a 55-degree temperature rise will give you about 3.4 gpm. This is enough for a standard shower (2.5 gpm) and maybe a small sink at the same time. (120 amps - requires min 200 amp service) More info on Bosch 5000 WH27 Electric Tankless Water Heaters ... click here

Stiebel Eltron Tempra 20 Electric Tankless Water Heater with a 50-degree water input and a 55-degree temperature rise will give you about 2.3 gpm. This is enough for a standard shower (2.5 gpm) in warm climates. (80 amps - requires min 150 amp service) More info Stiebel Tempra 20 Electric Tankless Water Heaters ... click here

Stiebel Eltron Tempra 24 Electric Tankless Water Heater with a 50-degree water input and a 55-degree temperature rise will give you about 2.9 gpm. This is enough for a standard shower (2.5 gpm) (80 amps - requires min 160 amp service) More info Stiebel Tempra 24 Electric Tankless Water Heaters ... click here

Stiebel Eltron Tempra 29 Electric Tankless Water Heater with a 50-degree water input and a 55-degree temperature rise will give you about 3.6 gpm. This is enough for a standard shower (2.5 gpm) and maybe a small sink at the same time. (120 amps - requires min 200 amp service) More info Stiebel Tempra 29 Electric Tankless Water Heaters ... click here

Stiebel Eltron Tempra 36 Electric Tankless Water Heater with a 50-degree water input and a 55-degree temperature rise will give you about 4.5 gpm. This is enough for a standard shower (2.5 gpm) and maybe a small sink at the same time. Possible 2 showers at the same time in warm climates. (120 amps - requires min 300 amp service) More info Stiebel Tempra 36 Electric Tankless Water Heaters ... click here


Specialty Uses
  • Bosch Tronic 3000 Point-of-Use US 3, US 6, US 7, US 9 and US 12
  • Bosch Tronic 3000T ES2.5, ES 4 and ES 8
Bosch 3000 Whole House Point-of-Use Electric Tankless Water Heater - check specifications for these heaters. None of these units should be used for showers. These heaters replace the PowerStar Point of Use Electric Tankless Water Heaters ... click here

Ariston - check specifications for these heaters. These are mini-tanks for 1 - 2 or 3 sinks. More info on the Ariston Mini Hot Water Tank ... click here



What is a typical use? **
Appliance Flow Rate GPM
Bathroom Faucet 1.0
Bath Tub 4.0 to 5.0
Shower 2.5
Multi Shower Heads 2.5 to 12
Kitchen Sink 1.5
Dishwasher 1.5
Washing Machine 2.0


Please note: These numbers may not reflect your appliances or fixtures due to differences in water pressure from location to location. Differences are also due to efficiency of appliances and fixtures.

If you have a multi shower head system - you need to find out how much water all the shower heads will consume per minute. Make sure the tankless water heater you use will provide the correct amount of hot water. If you don't see one - contact us and we will advise you how to use a tankless water heater with a multi-shower head system.


One last thing: We are assuming that your input water (ground) is 50-degrees. Your actual input water may be slightly colder (not likely) or very much warmer (likely in warm climates). You should check and review your input water temperature before relying on any of the above numbers. If your ground water is colder - then you will get less output - if your ground water is warmer - then you will get more output.
Average ground water in the USA is between 50 and 55-degrees winter to summer.




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