A tank water heater keeps a set amount of water hot and ready, while a tankless unit heats water only when you open a tap. Tankless gives you a steady supply and saves space; a tank is simpler to install and handles several fixtures at once. Your household's hot water use and your gas and venting setup decide the fit.
How does a tank water heater work?
A tank water heater stores water and keeps it at temperature around the clock, using a gas burner or electric elements. When the hot water runs out, you wait for it to recover.
Tank capacity and first-hour rating tell you how much hot water you can use in a busy hour. Because the tank stays hot even when nobody is using water, it loses some heat while it sits. That is called standby loss.
Tanks need simple upkeep: a periodic flush to clear sediment, a check of the T&P valve, and an anode rod that protects the tank from corrosion.
How does a tankless water heater work?
A tankless water heater fires up when it senses water flowing and heats it as it passes through. There is no stored water, so there is no tank to run dry.
Tankless output is measured by flow rate in gallons per minute. The supply does not run out, but a unit can only heat so many gallons per minute at once, so running two showers and a dishwasher together needs the right size unit.
Gas tankless units often need a larger gas line and different venting than the tank they replace. Hard water can build scale inside the heat exchanger, so tankless units need periodic descaling.
What are the pros and cons of each?
Tankless wins on endless supply and space. A tank wins on simpler installs and serving several fixtures at once without upsizing.
- Tank pro: straightforward replacement when swapping like for like.
- Tank pro: stored hot water covers several fixtures at the same moment.
- Tank con: you can run out of hot water during a busy stretch.
- Tank con: standby heat loss while the water sits in the tank.
- Tankless pro: hot water keeps coming as long as you need it.
- Tankless pro: mounts on a wall and frees up floor space.
- Tankless con: may need gas line and venting changes during install.
- Tankless con: needs regular descaling, especially with hard water.
Which one fits your household?
If your family runs out of hot water or you want floor space back, tankless is worth a look. If your current tank serves you fine, a like-for-like tank is often the simpler choice.
Think about how many bathrooms you have, how many people shower in the morning, and whether you fill a big tub. Then think about the install: where the unit sits, whether you have gas, and how it vents.
Upfront cost is usually higher for tankless because of the unit and any gas or venting work, while a tank has standby loss over time. We do not publish installation prices because every home is different, but your estimate will show both paths if both make sense.
What does CASC install and how do we size it?
CASC installs Bradford White tank water heaters and Rinnai tankless water heaters, and we are a Rinnai PRO. Water-heater installs come with a free estimate.
At the estimate we look at your current unit, your fuel type, venting, gas line and the space, then ask how your household uses hot water. Licensed and certified technicians handle the install and pull required permits.
We also offer a water-heater flush for $159. Financing options available.
How do Tank water heater and Tankless water heater compare?
| Question | Tank water heater | Tankless water heater |
|---|---|---|
| How it works | Stores water and keeps it hot | Heats water on demand as it flows through |
| Good fit for | Homes happy with their current supply; simple like-for-like swaps | Homes that run out of hot water or want floor space back |
| Hot water supply | Limited by tank size and first-hour rating | Continuous, limited by flow rate (GPM) |
| Efficiency | Some standby heat loss while water sits | No standby loss; heats only when used |
| Upfront vs running cost | Usually simpler and lower upfront | Usually higher upfront; gas line or venting may change |
| Maintenance | Flush sediment, check anode rod and T&P valve | Periodic descaling and inlet filter cleaning |
| Space and install | Floor space for the tank | Wall-mounted; needs proper gas supply and venting |
| What CASC installs | Bradford White | Rinnai (CASC is a Rinnai PRO) |
We do not publish installation prices. Water-heater installs get a free estimate.
Frequently asked questions
Will a tankless water heater never run out of hot water?
It will keep heating as long as water flows, but it has a flow-rate limit. If too many fixtures run at once, the water can cool. Sizing the unit to your household avoids that.
Can I switch from a tank to tankless?
Often, yes. Gas tankless units may need a larger gas line and new venting, so we check both during your free estimate before recommending it.
How often should each type be maintained?
Tanks benefit from periodic flushing to clear sediment, and tankless units need descaling, especially with hard water. Your technician can suggest a schedule based on your water and usage.
Do you service water heaters you did not install?
Yes. CASC services major brands, and repair visits start with a service call: $99 on weekdays and $149 on weekends and holidays.
Terms on this page
Related guides
- How a tank water heater works and how to make it last A tank water heater stores and heats water in an insulated tank using a gas burner or electric elements. Cold water enters at the bottom through a dip tube, and hot water leaves from the top. Flushing sediment, checking the anode rod and testing the relief valve help it last longer.
- How tankless water heaters work A tankless water heater heats water only when you open a hot tap. A flow sensor fires a gas burner, and water passes through a heat exchanger on its way to your faucet. Output is limited by flow rate and how much the water must be warmed, so sizing, gas supply and periodic descaling all matter.
- Rinnai tankless water heaters Rinnai makes gas tankless water heaters that heat water as it flows, so you don't run out the way a tank can. CASC is a Rinnai PRO and installs Rinnai tankless units across Central Arkansas, sizing the unit to your fixtures, checking gas and venting, and registering your equipment.
- Get a free replacement estimate CASC gives free estimates on HVAC replacements, larger plumbing projects like water-heater installs, repipes and sewer replacements, and commercial HVAC projects. A technician visits, looks at your current equipment and home, sizes the job and walks you through options. Request yours through our contact form or call 501-307-1310.
Ready to compare both options for your home?
Request a free water-heater estimate. We'll check your gas, venting and space, then show you the tank and tankless options that fit.
Request a free estimate