How each one runs out
A tank runs out when the stored hot water is used up, then needs time to recover. A tankless unit heats water as it flows, so it never runs dry, but it has a maximum flow rate. Two showers and a dishwasher at once can push it past that rate and the water turns lukewarm.
What has to be true for tankless
- Gas supply. Tankless units use a lot of gas while running. Many houses need a larger gas line from the meter.
- Venting. Condensing models vent through PVC out a side wall, so the old chimney connection is not used.
- Water quality. Hard water scales the heat exchanger. Plan on flushing it yearly, or adding a softener.
Over ten years
Tankless costs more to install and less to run, and typically lasts longer than a tank. Whether the fuel savings cover the higher install price depends on how much hot water the household uses and what the gas line and venting work costs at your house. We price both on the same visit so you can compare directly.
When a tank is the better choice
- Large households that run several fixtures at once
- Houses where the gas line or venting work would be extensive
- Budgets where the lower upfront cost matters more than the running cost