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How-To & Guides 8 min read • Jun 21, 2026

Tankless Gas vs. Hybrid Electric Water Heaters: Texas Installation Costs & Gas Line Sizing

Sizing tankless water heaters for simultaneous Texas showers. Gas supply BTU requirements, direct-vent concentric piping, water treatment, and electrical upgrades.

Tankless water heaters provide endless hot water and free up valuable interior square footage. Proper gas supply line sizing and annual descaling protect heat exchangers from premature failure.

Sizing GPM Flow Rates for Texas Ground Water Temperatures

Texas winter inlet water temperatures average 55°F to 60°F. Delivering 120°F water requires a 60°F to 65°F temperature rise:

  • 7.5 GPM Unit: Runs 2 simultaneous showers plus dishwasher.
  • 9.5 – 11.0 GPM Unit: Runs 3 to 4 simultaneous hot water fixtures in large multi-bath homes.

Frequently Asked Questions

How much does it cost to install a tankless water heater in Texas?

Converting from a standard 50-gallon tank to an exterior or attic gas tankless unit averages $2,800 to $4,800 installed, including dedicated gas line upsizing and PVC/polypropylene venting.

Do tankless water heaters need bigger gas lines?

Yes. While a 50-gallon tank draws 35,000 to 40,000 BTUs, an on-demand whole-home tankless unit draws 160,000 to 199,000 BTUs, often requiring upgrading the gas supply line from 1/2" to 3/4" or 1".

How often do tankless water heaters need flushing in Texas?

Due to high calcium and magnesium levels in Texas municipal water, tankless heat exchangers must be flushed with food-grade vinegar or descaling solution every 12 months to maintain warranty coverage.

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