Natural gas and propane tankless
Gas Tankless Water Heater San Antonio
Need hot water for a busy household? An experienced local installer can size a gas tankless unit and handle the gas line and venting.
Call (726) 268-4856- Natural gas and propane
- Indoor and outdoor units
- No obligation to hire
Last updated November 8, 2026
Sizing
Tankless Gas Hot Water Heater Sizing
At a glance
- Size by the GPM of fixtures that run at the same time, at your winter temperature rise.
- Whole-house gas units are rated in BTUs, often 120,000 to 199,000 BTU per hour.
- Many homes need a larger gas line from the meter for a gas tankless unit.
- Call (726) 268-4856 to be connected with an independent installer.
A tankless gas hot water heater is sized by flow rate. Add the gallons per minute of fixtures that may run at once: about 2 GPM per shower and 1 to 1.5 GPM per faucet. Then check the unit's GPM at the temperature rise you need in winter.
A tankless gas water heater for a 2 to 3 bathroom San Antonio home is often rated around 7 to 10 GPM. Larger homes may use a bigger unit or two units linked together.
We connect you with an independent installer who sizes and installs gas tankless units.
Gas and venting
Gas Instantaneous Water Heater Venting and Gas Line Size
A gas instantaneous water heater burns far more gas per hour than a tank heater while it runs. The gas line, regulator and meter must deliver that full flow, or the unit will cut out during heavy use.
- Gas line: often upsized from the meter to the unit, based on BTU rating and pipe length.
- Venting: condensing units use PVC or polypropylene venting; non-condensing units use stainless steel. Outdoor units vent through their own cabinet.
- Condensate: condensing units produce acidic condensate that needs a drain and often a neutralizer.
- Power: the unit needs a 120-volt outlet for its fan and controls.
Fuel options
Propane Tankless Water Heater and Natural Gas Tankless Water Heater
Most tankless models come in natural gas and propane (LP) versions. They are not interchangeable without the manufacturer's conversion kit.
Natural gas tankless water heater
Common inside San Antonio city limits. The CPS Energy meter and line size set how large a unit can be.
Propane tankless water heater
Common in rural areas around Helotes, Boerne and the outskirts. An LP tankless water heater draws from a propane tank, so tank size and regulator matter.
Propane on demand water heater for small spaces
Compact propane on demand water heater models suit workshops and casitas.
Going gas tankless? Get your gas line checked first.
Call (726) 268-4856Quotes
What Affects Gas Tankless Water Heater Installation Cost?
Gas tankless water heater installation cost depends mostly on the gas line, venting and location. Replacing an existing tankless unit is simplest. Converting from a tank usually adds a larger gas line, new venting, a condensate drain and an outlet.
Each contractor quotes their own work after seeing the home. See the tankless cost page for all the factors.
Homeowner questions
Gas Tankless FAQs
Will my gas line support a tankless water heater?
Many existing lines sized for a tank heater are too small for a whole-house tankless unit. The installer calculates the required size from the unit's BTU rating and the pipe length.
Condensing or non-condensing tankless?
Condensing units are more efficient and vent with PVC, but they need a condensate drain. Non-condensing units use stainless venting. The installer can explain which suits your home.
Can a gas tankless unit go outside?
Yes. Outdoor models are popular in San Antonio and avoid indoor venting. They need power for freeze protection.
What is the best tankless water heater, gas or electric?
For larger households, gas usually delivers more hot water. Electric suits smaller homes and homes without gas.
Do you install gas tankless water heaters?
We are a free referral service. We connect you with an independent local installer who quotes and performs the work.
Get Connected With a Gas Tankless Installer
Tell us about your home, fuel and current water heater. We will connect you with an independent local installer who can quote the job. No obligation to hire.