Tankless Water Heaters: How to Choose, Size & Install (Gas, Electric, Whole-House & Point-of-Use)
Tankless Water Heaters: Delivering cost savings
A tankless water heater delivers hot water on demand with impressive tankless water heater efficiency, compact size, and long service life. This guide covers how to choose a tankless water heater, a practical tankless water heater sizing guide, gas vs. electric differences, installation basics, cost considerations, and maintenance & parts—plus links so you can buy tankless water heaters online from our curated selection.
Benefits of a Tankless Water Heater
- Endless hot water—right-sized units keep up with multiple fixtures.
- Higher efficiency—especially with condensing tankless water heater models that reclaim heat from exhaust.
- Space savings—small wall-mount form factor.
- Longer life—serviceable parts and routine maintenance extend lifespan.
- Lower standby cost—no tank reheating all day.
Gas vs. Electric (Which Is Right for You?)
| Type | Best For | Notes |
|---|---|---|
| Gas Tankless Water Heater | Whole-house with higher flow (multiple showers, laundry) | Needs proper gas line sizing & venting; condensing gas is most efficient. |
| Electric Tankless Water Heater | Point-of-use, smaller homes, or where gas/venting is difficult | Needs ample electrical service (high-amp circuits); no combustion/venting. |
Whole-House Tankless Water Heaters Gas Tankless Options Electric Tankless Options Point-of-Use Tankless Condensing Tankless
Tankless Water Heater Sizing Guide (Quick Math)
- Count fixtures simultaneously in use (e.g., shower + kitchen sink).
- Add flow rates (GPM) at those fixtures (typical shower ~2.0–2.5 GPM; faucet ~1.0–1.5 GPM).
- Estimate temperature rise = desired outlet temp (e.g., 120°F) − your inlet ground water temp.
- Match to a unit’s curve: Choose the model that hits your required GPM at your temperature rise (e.g., 5–7 GPM @ 70°F rise for many 1–2 bath homes).
Example: Two showers at 2.0 GPM each + a 1.0 GPM faucet = 5.0 GPM. If your winter groundwater is 50°F and you want 120°F, that’s a 70°F rise. Pick a model that can deliver ~5 GPM at ~70°F rise.
Tankless Water Heater Installation (Overview)
- Location & clearances: Follow the manual; indoor gas units need proper venting/air supply.
- Gas line or electrical capacity: Confirm fuel type and size circuits/gas piping per specs.
- Venting (gas): Use listed materials; condensing models use cool exhaust and require condensate drain.
- Water treatment: Hard water? Add a scale inhibitor or plan regular descaling.
- Local code & warranty: Many brands require licensed installation and registration for full tankless water heater warranty coverage.
Maintenance & Parts
Tankless water heater maintenance is simple: flush/descale annually (more often with hard water), clean inlet screens, and keep combustion air/vents clear. If you ever need tankless water heater parts or tankless water heater repair, we carry OEM kits and accessories.
Explore These
Electric Tankless
Point-of-Use Tankless
Install & Vent Kits
Maintenance / Flush Kits
Tankless Water Heater Cost: What to Expect
- Equipment: Varies by size (GPM) and technology (condensing vs non-condensing).
- Installation: Venting, gas/electrical upgrades, and location can affect labor.
- Operating cost: Efficient, on-demand heating reduces standby losses vs. tanks.
- Warranty: Register your unit; keep proof of professional install if required.
Tankless Water Heater FAQs
What size tankless water heater do I need?
Match your peak GPM to your temperature rise. Many 1–2 bath homes need ~5–7 GPM at ~70°F rise. Use our sizing steps above or ask us for help.
How long does a tankless water heater last?
Often 15–20 years with proper maintenance (annual flush/descale, clean inlet screens, clear vents/air intakes).
Can I install a tankless water heater myself?
Some jurisdictions allow DIY electric/point-of-use installs; whole-house gas typically requires a licensed professional for gas line sizing, venting, and warranty compliance.
Do tankless water heaters work with hard water?
Yes, but plan for regular descaling or add a scale inhibitor. Hard water reduces efficiency if not maintained.
Are condensing models worth it?
Condensing gas models offer higher efficiency and cooler exhaust (easier venting in many cases). They also require a condensate drain.
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