Short answer
A tank water heater stores 40–80 gallons of hot water and costs less to install. A tankless unit heats water on demand, so it doesn't run out and saves space, but costs more upfront and often needs a larger gas line and new venting. Tankless suits high, steady demand; tanks suit simple like-for-like replacement.
Side-by-side comparison
| Tank | Tankless | |
|---|---|---|
| Hot water supply | Limited to tank size and recovery | Continuous, limited by flow rate |
| Upfront cost | Lower | Higher (unit plus gas/vent work) |
| Space | Large footprint | Wall-mounted |
| Maintenance | Flush sediment, check anode | Descale heat exchanger regularly |
| Typical life | About 8–12 years | Often longer with maintenance |
| Power outage (gas) | Many still work | Most need electricity |
When tankless makes sense
- You run out of hot water with back-to-back showers
- You're replacing an old tank anyway
- Space is tight
- Your gas supply and vent route can support it
When a tank is the better choice
- You want the fastest, lowest-cost replacement
- Your hot water use is modest
- Upgrading the gas line or venting would be complicated
Side-by-side comparison
| Factor | Tank | Tankless |
|---|---|---|
| Upfront cost | Lower | Higher, especially with gas line or vent upgrades |
| Hot water supply | Limited by tank size | Continuous, limited by flow rate |
| Lifespan | About 8–12 years | About 15–20 years with maintenance |
| Space | Floor space for the tank | Wall-mounted, compact |
| Maintenance | Annual flush, anode checks | Descaling every 1–2 years |
| Power outage (gas) | Often still works | Needs electricity to run |
What it costs to switch in an existing home
Converting from a gas tank to gas tankless often means a larger gas line, new venting and a dedicated electrical outlet. Converting to electric tankless usually needs a large electrical upgrade. Those extras can be as much as the unit itself, so get an installed price, not just the equipment price, when comparing options.
When to call a plumber
If the steps above don't solve it, or anything involves sewage, gas, electricity near water or a leak you can't stop, call a licensed plumber. Related help: tankless water heaters in Gastonia, water heater replacement in Gastonia, water heater repair in Gastonia.
Where this comes up most in Gaston County: Willow Creek, Loray Mill Village, Forest Heights, Belmont, NC, Mount Holly, NC, Cramerton, NC, McAdenville, NC, Lowell, NC. See all Gastonia and Gaston County service areas.
Frequently asked questions
Does a tankless water heater save money?
It can reduce standby energy loss, but higher installation cost means payback depends on usage. It's often chosen for endless hot water and space rather than savings alone.
Can tankless heaters handle two showers at once?
If sized for the combined flow rate. Undersized units drop temperature when several fixtures run.
Editorial note: this guide gives general safety and maintenance information for homeowners. It doesn't replace an on-site diagnosis by a licensed plumber. Codes and permit rules can change; check with your local inspections office.