What it isMoving to a tankless heater is more than a swap. Gas tankless units typically need a larger gas supply than a tank heater, dedicated venting, and sometimes a condensate drain. Electric tankless units may need significant electrical capacity. Getting sizing and supply right is what separates a good install from a frustrating one.
When you need tankless water heater installation
- Replacing a failed tank and wanting continuous hot water
- Freeing up floor space
- Large tubs or households where tanks run out
How it works
- Calculate peak flow (gallons per minute) and temperature rise based on incoming water temperature.
- Check gas meter and line sizing, or electrical service capacity.
- Plan venting route (concentric, PVC for condensing, or stainless for non-condensing).
- Mount the unit, install service valves for descaling, and connect water, gas and venting.
- Commission the unit and set temperature.
How it compares
| Item | Tank | Tankless |
|---|---|---|
| Hot water supply | Limited by tank size | Continuous within flow rating |
| Space | Floor footprint | Wall-mounted |
| Gas demand | Lower | Higher BTU input |
| Maintenance | Flushing, anode | Descaling, filter cleaning |
Limits and when it’s not the right fix
- Cold climates require more capacity because incoming water is colder.
- Hard water shortens service intervals unless treated.
What affects the cost
We don’t publish national price figures because real quotes vary too much by region, access and the condition of your system. These are the factors that move the price:
- Unit capacity
- Gas line upgrade
- Venting
- Condensate drain
- Recirculation option
- Permits
Ask for a written quote that names the method, materials and any permit or restoration work before work begins.
Tankless Water Heater Installation: common questions
Can a tankless water heater run a whole house?
Yes, if sized for the number of fixtures used at once and the local temperature rise. Large homes sometimes use two units.
Does a tankless water heater need a bigger gas line?
Often. Many gas tankless units have a much higher BTU input than tank heaters, so the existing line and meter must be checked.
Do tankless heaters work in cold climates?
They do, but colder incoming water reduces how many gallons per minute they can heat, so sizing must account for winter conditions.
