How Long Does It Take For Hot Water to Come Back After a Shower?

The amount of time it takes for hot water to recover after a shower depends on several key variables of your water heating system.

Professional help is always welcome, just not the bill at the end

Why Does Hot Water Run Out?

The most common reason hot water runs out is due to the limitations of your water heater's storage tank and recovery rate. In a typical tank-style water heater, you have a finite amount of hot water stored (usually 40-80 gallons depending on tank size).

When you use hot water, cold water enters the bottom of the tank to replace it. As this happens, the cold water entering the tank needs time to heat up to the set temperature (typically 120-140°F).

From there, the recovery rate, or, how quickly your heater can warm new water, depends on BTU rating and burner efficiency (for gas burners) and wattage and element condition (for electric heaters).

Common Reasons Why Water Runs Out Quickly

Sediment buildup - calcium and magnesium due to hard water - at the bottom of the tank reducing efficiency
Failing heating elements (in electric heaters)
Thermostat issues
An undersized water heater tank for household demands
Multiple simultaneous hot water uses (shower + dishwasher + laundry)
Broken dip tube (mixes cold water with hot in the tank)

Recovery Rates

The most important factor is your water heater's recovery rate, which is how quickly it can heat new water entering the tank. For a typical 50-gallon gas water heater, it takes about 30-45 minutes to fully heat a tank of cold water. Electric water heaters generally take longer, around 60-80 minutes, due to less efficient heating elements.

Let's break down what's happening inside your system. When you shower, you're drawing hot water from the top of the tank while cold water enters at the bottom. This cold water needs time to heat up to your set temperature (typically 120-140°F). The actual recovery time depends on several variables.

Water heater size. A larger tank provides more hot water but takes longer to heat fully. For example, a 40-gallon tank will recover faster than an 80-gallon one.
Fuel type. Gas heaters recover roughly twice as fast as electric ones because they can transfer heat more efficiently. A gas heater might give you usable hot water in 20 minutes, while an electric unit could take 30 minutes or more.
Ground water temperature. In colder climates where the incoming water supply might be 40°F, heating takes longer than in warmer regions where ground water might be 60°F. Each 10-degree difference in incoming water temperature can affect recovery time by 5-10 minutes.
Usage patterns. If you're taking back-to-back showers (teenagers!), you're not waiting for a full recovery, you're using the remaining hot water while new water heats. This is why the third or fourth person might run out of hot water completely. Parents go to work and kids only go to school, so adjust accordingly.

How to Measure Your Water Heater's Recovery Time

Recovery rate is measured in GPH (Gallons Per Hour) raised through a 100°F temperature rise.

Recovery Rate (GPH) = (BTU/hr input × Efficiency Factor) ÷ (8.33 × 100°F rise)

Where 8.33 is the weight of one gallon of water in pounds and 100°F is the standard temperature rise used for ratings

Standard Residential Gas Water Heater

BTU input: 40,000 | Efficiency: 0.62 (62%)

Recovery Rate = (40,000 × 0.62) ÷ (8.33 × 100)
= 24,800 ÷ 833
= 29.8 GPH

High-Efficiency Gas Water Heater

BTU input: 40,000 | Efficiency: 0.82 (82%)

Recovery Rate = (40,000 × 0.82) ÷ (8.33 × 100)
= 32,800 ÷ 833
= 39.4 GPH

Electric Water Heater (4500W element)

BTU input: 15,354 (1W = 3.412 BTU/hr) | Efficiency: 0.95 (95%)

Recovery Rate = (15,354 × 0.95) ÷ (8.33 × 100)
= 14,586 ÷ 833
= 17.5 GPH

How Do I Calculate My Specific Heater's Recovery Rate?

To calculate for your specific model, you'll need to know BTU input rating and the Efficiency rating. These can be found on the manufacturer's label and on the EnergyGuide label. Plug these numbers into the formula(s) above.

The ratings will be different based on the type of water heater. For instance, a tankless water heater vs. storage tank unit will perform differently due to the former's on demand nature and the latter's capacity to heat water and retain it.

Ways to Warm Up Your Shower

You can control how much hot water you use by installing a low flow shower head. 52% Americans prefer a very warm shower, and a few of those folks can be careless with how much hot water they let flow through the pipes while lathering up and rinsing off.

Typically the kids who don't pay the monthly utility bills, am-I-rite!? So, limiting the amount of water in a hot shower is an effective way to keep a full tank for the next person.

You can also adjust the thermostat on the unit. We do not prefer scalding showers, and so we turn down the HVAC temp setting to be a bit more energy efficient. Science and math aside, it sure feels like the hot water tank reheats a bit faster this way.

We also recommend showering at times when no one is washing dishes or their clothes. That kitchen faucet bleeds a lot more hot water than you think scrubbing all those pots and pans from dinner.

Things to Remember

Actual recovery rates may be lower due to mineral buildup and age. Further, local water temperature and environment affects performance. And when it comes to planning, First Hour Rating (FHR) is often more useful than recovery rate alone.

Water Heater Repair

Homeowners that find consistent issues with not having enough hot water should call a professional plumber to assess whether or not their unit is malfunctioning. A new water heater, while more efficient, will run you a few bucks.