Yes, you can absolutely use an instant (tankless) water heater for a shower. However, because they heat water on demand, you must ensure the unit's kilowatt (kW) or wattage rating is high enough to handle your shower's flow rate.
To size a tankless water heater, add up the maximum flow rate (GPM) of all fixtures you plan to run simultaneously. For a single typical shower using 1.51.51.5 to 2.52.52.5 GPM, you generally need a 131313 kW to 242424 kW electric unit or a 140,000 BTU gas unit, depending on your climate.
A tankless water heater cannot provide hot water faster than its ability to heat the water. While a tank unit can provide hot water for multiple uses at once, a tankless unit might not be able to support simultaneous usage, such as washing dishes, taking a shower and running a washing machine all at once.
If a standard showerhead is fitted, it will use around an extra half a gallon each minute, accounting for a 25-gallon emittance every 10 minutes, or 50 gallons throughout a 20-minute shower. *1 gallon = 4.54 litres.
A typical tankless water heater's lifespan often ranges from 15 to 20 years or more with proper care. In many cases, well-maintained systems can reach 25 to 30 years of service.
Homes with one or two bathrooms typically need a tankless water heater rated for 6-7 GPM. This capacity handles two showers running simultaneously plus light kitchen or laundry use.
Drawbacks of Tankless Water Heaters
As discussed above, the biggest downside of owning a tankless water heater is its higher cost. The initial installation and unit costs are more expensive than a traditional storage-tank water heater.
The 4-minute shower rule is a sustainability and cost-saving initiative advising people to limit their daily showers to four minutes or less. This practice helps conserve water, reduce energy used for heating, and lower household utility bills by limiting consumption to approximately 36–40 liters (roughly 9.6–10.5 gallons) per shower.
Some common causes of high water bills include:
A 20-minute shower almost always uses more water than a bath.
A tankless water heater usually goes cold mid-shower because the water flow drops below the heater's minimum activation threshold, or the system is overloaded by using too many fixtures at once. It can also happen if sediment blocks the filter or the unit is improperly sized.
Tankless water heater installation costs between $1,404 and $3,899 for your home, depending on unit size and setup. The fuel type you choose shapes your upfront and utility costs, with electric lower-priced and solar earning tax credits.
Yes, a tankless water heater can fill a bathtub. Because tankless systems heat water on demand, they provide a continuous stream of hot water, which prevents you from running out halfway through filling a large soaking tub.
Plumbers often hesitate to recommend tankless water heaters because they act like high-performance sports cars. Unlike traditional tank models that are "workhorses" and can function while mostly ignored, tankless units require precise installation, regular maintenance, and are highly sensitive to mineral buildup.
Here is a simple way to decide: Choose Navien if you want the highest efficiency, longest warranty, and built-in recirculation. Choose Rinnai if you have a large household and need the highest flow rates. Choose Rheem if you want a reliable brand at a lower price point.
Yes, you can absolutely use an instant (tankless) water heater for a shower. However, because they heat water on demand, you must ensure the unit's kilowatt (kW) or wattage rating is high enough to handle your shower's flow rate.
Top 5 Water Wasters in Your Home
A 10-minute shower typically uses 15 to 25 gallons (57 to 95 liters) of water. The exact amount depends on your showerhead's flow rate:
A bathtub filled with 80 litres of water works out cheaper than a 10-minute shower using 100-150 litres of water.
The #1 water waster in your home is the toilet.
A leaking toilet can waste 15,000 gallons of water a month.
Showers: Longer or more frequent showers, especially with guests, can significantly increase water use. A single 10-minute shower can use 20–50 gallons.
(a) Caption: Toilets are the largest indoor water use for the average American, but many other uses contribute significantly to overall water usage.
Most seniors only need to shower or bathe two to three times per week to maintain proper hygiene. Because aging skin is thinner, drier, and more prone to cracking, excessive washing can strip away natural oils and lead to irritation.
H.R. 4593, the SHOWER Act—Rep.
The Energy Policy and Conservation Act (EPCA) defines “showerhead” broadly and, under current law, allows the maximum water use for any showerhead to be 2.5 gallons per minute (GPM) when measured at a flowing water pressure of 80 pounds per square inch.
Skipping showers for four days is generally safe and causes no lasting medical harm. However, your body’s natural oils and dead skin will accumulate. You will likely experience a greasy scalp and strong body odor. Minor itching or irritation may also occur as bacteria feed on sweat and oils.