Is tankless worth it in a Roanoke home?
A tankless (on-demand) heater only fires when a hot tap is open, so it doesn't spend energy keeping 40 or 50 gallons hot all day. The U.S. Department of Energy estimates that for homes using 41 gallons or less of hot water a day, demand heaters can be 24% to 34% more energy efficient than a storage tank, and 8% to 14% more efficient in homes that use around 86 gallons a day (Energy Saver). Most units also last longer than a tank.
Good fit
- Gas already at the water heater
- You run out of hot water with a tank
- You want the floor space back
- Planning to stay in the house for years
Think twice
- Small gas line that can't be upsized easily
- Older electric service, for electric whole-house units
- Very hard water and no plan to descale
- Selling the house soon
Sizing for January, not July
A tankless heater is rated by how many gallons per minute it can raise by a given temperature. In winter, incoming water is much colder, so the same unit delivers less hot water. Size it for the worst case: for example, two showers and the dishwasher at once on a cold morning. An undersized unit is the most common tankless complaint, and it's avoidable.
What a conversion from a tank involves
- Gas supply. Gas tankless units draw far more gas at full fire than a tank heater, so the line often has to be upsized from the meter. See gas line work.
- Venting. Most units vent through a sidewall with PVC or stainless pipe rather than the old chimney flue.
- Electrical. Gas units need a standard outlet. Electric whole-house units usually need large dedicated circuits.
- Isolation valves. Service valves let the unit be flushed without cutting into pipe later.
- Permit and inspection. The City of Roanoke's Business Owner's Guide lists water heater installation among jobs that need a plumbing permit.
Descaling and repair
Hard water leaves scale on the heat exchanger, which shows up as fluctuating temperature, error codes or reduced flow. Flushing with a descaling solution through the service valves, usually once a year or as the manufacturer recommends, keeps the unit efficient. Error codes, ignition failures and cold-water "sandwich" bursts are common repair calls.
Common questions
How much does a tankless conversion cost compared to a tank?
More up front, because of the unit itself plus gas, venting and electrical work. The gap shrinks when the home already has an adequate gas line and a convenient outside wall for venting. Get a quote that lists those items separately.
Will tankless give me endless hot water?
Yes, as long as the unit is sized for how many fixtures you run at once. It won't run out like a tank, but it can only heat so many gallons per minute.
Can I put a tankless heater where my old tank was?
Usually, if venting can reach an outside wall from there. Some homes move the unit to a garage or exterior wall instead.
Gas or electric tankless?
Gas units deliver more hot water per minute and suit most whole-house installs. Electric units suit smaller homes or point-of-use spots, but whole-house models need a lot of electrical capacity.