One of the most common questions I get from Marathon County homeowners is whether to replace their old tank heater with a tankless unit. Both work well — but they work differently, and the right choice depends on your hot water usage, home setup, and budget. Here's my honest comparison after 61 years of installing both.
Tank water heaters store 40–80 gallons of hot water, keeping it ready on demand. Gas units heat water faster; electric units cost less upfront but have higher operating costs in most cases. They're simpler to install and service, have lower upfront costs, and work well for most family homes.
Tankless (on-demand) water heaters heat water as you need it — no storage tank. They're more energy-efficient because they don't maintain standby heat. Gas tankless units can provide unlimited hot water; electric tankless units have higher power demands and may require electrical panel upgrades.
Conventional tank: $400–$900 for the unit, plus $300–$600 installation. Tankless gas: $700–$1,500 for the unit, plus $500–$1,200 installation (may need gas line upgrade). Tankless electric: $200–$700 for the unit, but often requires a $1,000–$2,000 electrical upgrade for adequate amperage.
Tankless units are 20–30% more energy efficient than tank units on paper. In practice, Wisconsin homes with high hot water usage (family of 4+) see meaningful savings. For smaller households with lower hot water usage, payback period can be 8–12 years — by which time a tank heater would need replacement anyway.
Choose a tank heater if: your budget is tight, your home has adequate space, you have a smaller household, or you're replacing a failing unit urgently (tank heaters can usually be installed same-day; tankless sometimes requires scheduling a gas line or electrical upgrade).
Choose tankless if: you have a large household with simultaneous hot water demands, you want lower long-term operating costs, you have limited space (tankless units are wall-mounted), or you're building new or doing a major renovation with flexibility for gas/electrical upgrades.
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A properly sized gas tankless water heater will not run out of hot water — it heats continuously on demand. An undersized unit can't keep up with simultaneous demand (e.g., shower + dishwasher + laundry). Proper sizing is critical — Genrich Plumbing sizes units for your household's peak demand.
Yes. Wausau area water is moderately hard, which can cause mineral scale buildup in both tank and tankless water heaters. Annual flushing (both types) extends lifespan significantly. Tankless heaters are more sensitive to scale buildup in the heat exchanger.
Not recommended for gas units — gas line work requires a licensed plumber. Not safe for electric units requiring panel upgrades — requires a licensed electrician. Improper installation voids warranties and creates safety risks. Call Genrich Plumbing at (715) 675-2000 for a professional assessment.
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