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Gas Tankless Water Heaters
Bosch AquaStar 2400ES
Bosch AquaStar 2400E
Bosch AquaStar 2400EO
Bosch AquaStar 2700ES
Bosch AquaStar 1600H
Bosch AquaStar 125FX
Bosch AquaStar 1600P
Bosch AquaStar 125BO
Bosch AquaStar 1600PS
Bosch AquaStar 125BS
Bosch AquaStar 1000P


Takagi T-KJr
Takagi T-K3
Takagi T-K3-OS
Takagi T-M1


Electric Tankless Water Heaters
PowerStar
PowerStream
Stiebel Eltron


Electric Mini-Tank Water Heater
Ariston
Stiebel Eltron SHC4


Oil Tankless Water Heaters
Toyotomi


RV and Boat Water Heaters
RV 500
Boat ShowerMate


Accessories
4" Z Flex Venting
3" Z Flex Vent
AQ1 Power-vent
AQ3 Side Vent Kit
FXHood
Webstones Valves
Water Connections



What Size?

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Tankless Water Heaters! Save Energy!
Tankless Water Heaters what size do you need?
This page will give you a quick-view look at all our 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.


Natural Gas Tankless Water Heaters or Propane Tankless Water Heaters
Click here for 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 AquaStar 1600P / 125B - Standing Pilot - Gravity Vent
  • Bosch AquaStar 1500H / 125HX - Hydron Spark Ignition - Gravity Vent
  • Bosch AquaStar 125FX - Electronic Ignition - Power Vent Horizontal Only
  • Bosch AquaStar 1600PS / 125BS - Standing Pilot - Solar Booster or as Stand-Alone heater - Gravity Vent
  • Takagi T-KJr - Electronic Ignition - Optional Direct Vent - Horizontal or Vertical Power Vented
Bosch AquaStar 1600 / 125 tankless water heaters will give you a max output of 4 GPM. 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...

Takagi T-KJr tankless water heater will give you about 4 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 180 degrees.
More info on the Takagi Tankless Water Heater...


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

  • Bosch AquaStar 2400ES / 2400E / 250SX - Electronic Ignition - Direct Vent - Horizontal or Vertical Venting
  • Bosch AquaStar 2400EO / 250SXO - Electronic Ignition - Outdoor Model
  • Bosch AquaStar 2700ES - Electronic Ignition - Direct Vent - Horizontal or Vertical Venting
  • Takagi T-K3 - Electronic Ignition - Horizontal or Vertical Power Vented - Optional Direct Vent
  • Takagi T-M1 - Electronic Ignition - Horizontal or Vertical Power Vented
Bosch AquaStar 2400E Tankless Water Heater will give you a max output of 6.35 GPM. A 50-degree water input and a 55-degree temperature rise will give you 5.3 gpm. Direct Vented (Sealed Combustion). Enough hot water for two standard showers (2.5 gpm each).
More info on the Bosch Aquastar 2400E Tankless Water Heater...

Bosch AquaStar 2400EO Tankless Water Heater will give you a max output of 6.35 GPM. A 50-degree water input and a 55-degree temperature rise will give you 5.3 gpm. Used for outdoor use only! Enough hot water for two standard showers (2.5 gpm each).
More info on the Bosch Aquastar 250SXO (Outdoor Model) Tankless Water Heater...

Bosch AquaStar 2700ES Tankless Water Heater will give you a max output of 7.15 GPM. A 50-degree water input and a 55-degree temperature rise will give you 5.9 gpm. Direct Vented (Sealed Combustion). Enough hot water for two standard showers and a bathroom sink too. (2.5 gpm each).
More info on the Bosch Aquastar 2700ES Tankless Water Heater...

Takagi T-K3 Tankless Hot Water Heater will give you a max output of 6.9 GPM. A 50-degree water input and a 55-degree temperature rise will give you about 6 GPM. This is enough for two standard showers (2.5 gpm each). The Takagi T-K3 can also be used for heating applications up to 180 degrees.
More info on the Takagi Tankless Water Heater...

Takagi T-M1 Tankless Hot Water Heater will give you a max output of 9.6 GPM. A 50-degree water input and a 55-degree temperature rise will give you about 7 GPM. This is enough for two standard showers (2.5 gpm each) and a sink at the same time. In warmer climits with input water at about 60-degrees - you should be able to run 3 single-shower head showers at one time. The Takagi T-M1 can also be used for heating applications up to 180 degrees.
More info on the Takagi Tankless Water Heater...




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

  • Takagi T-M1 - Electronic Ignition - Horizontal or Vertical Power Vented
  • Any of the Takagi Water heaters with used in conjuction with a storage tank


Takagi T-M1 Tankless Water Heater will give you a max output of 9.6 GPM. A 50-degree water input and a 55-degree temperature rise will give you about 7 GPM. This is enough for two standard showers (2.5 gpm each) and a sink at the same time. In warmer climits with input water at about 60-degrees - you should be able to run 3 single-shower head showers at one time. The Takagi T-M1 can also be used for heating applications up to 180 degrees.
More info on the Takagi Tankless Water Heater...


Specialty Uses
  • AquaStar 1000P / 38B - Standing Pilot
Bosch AquaStar 1000P Tankless Hot Water Heater will give you about 1 GPM with a 50-degree water input and 55-degree rise. The 1000P should not be used for showers. More info...



Electric Tankless Waters

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

  • PowerStar AE 115
  • PowerStar AE 125
  • Stiebel Eltron Tempra 20
  • Stiebel Eltron Tempra 24
  • Stiebel Eltron Tempra 29
  • Stiebel Eltron Tempra 36

PowerStar AE 115 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...

PowerStar AE 125 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...

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 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 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 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...


Specialty Uses
  • PowerStream /Powerstar POS RP1, RP3, RP2, RP7, RP12T
  • Ariston GL2.5, GL4 GL6+
PowerStream Electric Tankless Water Heater - check specifications for these heaters. None of these units should be used for showers. More info...

Ariston - check specifications for these heaters. These are mini-tanks for 1 - 2 or 3 sinks. More info...



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 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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