A 40-gallon hot water tank provides about 8 to 15 minutes of continuous hot water. This translates to about 13 to 20 minutes of actual shower time, as you normally mix the scalding tank water with cold water to reach a comfortable temperature.
Water Heater Size
Your tank size is the most significant determinant of how long you can have a hot shower: 30-gallon tank: ~5–7 minutes of hot water. 40-gallon tank: ~8–10 minutes. 50-gallon tank: ~10–12 minutes.
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.
If you limit your hot water activities to ONLY showers, a 40-gallon water heater could comfortably handle 2 average-length showers at the same time (17 + 17 = 34 gallons).
Water Heater Heating Times by Type
A typical 40-50 gallon gas tank will fully recover in about 30-40 minutes (or faster, depending on the model) after you've used up all the hot water.
A: Traditional tank water heaters usually last 8–12 years, while tankless units often last 15–20+ years.
The average shower water usage is calculated by multiplying that average flow rate of 2.1 gallons per minute by the average shower length of 8.2 minutes. So, 17.2 gallons is, on average, how much water is used. In a 10-minute shower, you'll go through 21 gallons. Water used in the shower can add up.
Typically, the rule-of-thumb is that you want a 40 gallon tank for 1 to 4 people, a 50 gallon tank for 4 to 6 people, and a 50 gallon high recovery or 75 gallon tank for 6 to 8 people.
Insufficient Water Heater Size
One of the most common reasons for running out of hot water quickly is that your water heater is too small for your household's needs. If your water heater doesn't have enough capacity to meet the demand during peak usage times, it will run out of hot water quickly.
A 40-gallon tank water heater installation costs $700 to $2,300, with an average cost of $1,650. Prices vary based on energy source and installation complexity. The national average cost to install a 40-gallon tank water heater ranges from $700 to $2,300.
Some common causes of high water bills include:
Your water heater relies on its heating element or burner to do the heavy lifting. If either of these parts starts to wear out or fails, the water inside your tank won't reach the temperature it should. This can cause your hot water to run out surprisingly fast, even if you haven't changed your usage.
Flush Facts
Design improvements have allowed toilets to use 1.28 gallons per flush or less while still providing equal or superior performance. This is 20 percent less water than the current federal standard of 1.6 gallons per flush.
Keep the top of the tank free of dust, debris and flammable products such as paint, gasoline, solvents or adhesives. Also, never use these products near a water heater or any other natural gas or electric appliance because vapors from flammable liquids can ignite.
Assuming you're mixing roughly half hot and half cold water, your 20 gallons of stored hot water effectively becomes 40 gallons of mixed shower water. This extends your shower time to around 16 minutes with a standard showerhead. Not bad for a quick rinse and wash!
Only heat the hot water twice a day
Try heating the water for an hour in the morning and an hour in the evening. Start the water heating about an hour before you need it. For example, if you shower at 08:30, start heating the water at 07:30. If you wash up in the evening at 19:30, then start the water heating at 18:30.
A malfunctioning water heater thermostat can cause your shower to run out of hot water quickly.
To help us save every drop of water, showers should be kept to four minutes or less. Wondering if cutting a couple of minutes off your shower really helps? The answer is yes!
Heat exposure from a hot shower, bath, or sauna session causes your blood vessels to expand - a process known as vasodilation. This results in increased blood flow and decreased blood pressure. A study published in the Journal of Physiology found that hot baths could help lower blood pressure [2].
Top 10 Water Heater Brands of 2026
It depends on your needs. If you have a large family or high water usage, a 50-gallon water heater is a good option. If you are on a budget or looking for an energy-efficient option, a 40-gallon may be the better choice.
A small (50- to 60-gallon) storage tank is usually sufficient for one to two three people. A medium (80-gallon) storage tank works well for three to four people. A large tank is appropriate for four to six people.
Toilet flushing, washing clothes, taking a bath or shower, dish washing and outdoor water uses are some of the main activities that use up the most water in a house.
In actuality, the average daily amount of hot water used per Australian is 76 litres (due to variances in showers, baths, and amount of chores completed). This translates into 1,596 litres per week and 6,840 litres per month for a family of three.
Think of baths as an occasional treat and stick to showers. The average bath uses 35 to 50 gallons of water, whereas a 10-minute shower with a low-flow showerhead only uses 25 gallons.