It takes about 60 to 120 minutes for a 40-gallon electric water heater to fully heat a tank of cold water from 50°F to a standard 120°F. The exact time depends primarily on the wattage of your heating elements, incoming water temperature, and whether you are heating an empty tank or recovering after use.
Electric tank water heaters are slower. That same 40-50 gallon tank will take 60-90 minutes to fully heat up again. Heating elements don't generate heat as quickly as gas burners, though they do transfer energy efficiently once they get going. With a larger 75-80-gallon electric tank, plan on waiting up to 2 hours.
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.
Electric Water Heaters
A typical electric hot water heater requires 60 to 80 minutes to heat a 40-50-gallon tank. Larger tanks may take longer. Electric water heaters use heating elements instead of burners, which explains the extended heating time.
For instance, a medium-sized, 40-gallon water heater that draws 4500 watts and is active for 2 hours a day at a rate of $0.13 per kilowatt-hour (kWh) costs about $1.17 to work per day, which comes to $35 each month or $426 each year.
Quick Answer: Monthly Electricity Usage
For most households, an electric tankless water heater consumes between 20-50 kWh per month. Here's a quick breakdown: Single person household: 8-15 kWh monthly. 2-person household: 15-25 kWh monthly.
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.
Electric water heaters: About 1-2 hours for a full tank. Gas water heaters: Usually 30-40 minutes. Tankless water heaters: Almost instant, since they heat water on demand. Recovering after use: Most tanks need about 20-30 minutes to reheat water after a shower.
Your Tank Might Be Too Small for Your Household
If you've recently added more people to your home or you're using more hot water than before, the issue might be with your tank size. A water heater that's too small will struggle to keep up with high demand.
With proper maintenance, a tank water heater tank should last six to 12 years. A tankless water heater can last for more than 20 years. Check your water heater's warranty for the most accurate timelines.
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. Energy consumption for 40 and 50 gallon standard water heaters is quite comparable.
Running out of hot water too quickly usually means sediment has reduced your tank's capacity, your dip tube has broken and is mixing cold water with hot, or your water heater is simply too small for your household's needs. Sediment buildup happens gradually and responds well to tank flushing.
A 40-gallon gas water heater typically delivers enough hot water for 2–4 people, supporting daily needs like showers, dishwashing, and laundry. Gas models heat water quickly, so recovery time between uses is shorter than with electric models.
The general rule of thumb is 1 hour for every 100 litres of water. So if your system isn't hot in 2.5 hours for a 250 Litre, it would be wise to contact Refined Plumbing.
Open the hot water tank drain valve. Let the water run out the garden hose. This can take 20 to 60 minutes, depending on how big the tank is.
40-gallon tanks (the most common residential size, suited for 2 to 3 people): Gas heats in 30 to 40 minutes; electric takes 60 to 80 minutes. 50-gallon tanks (great for families of 3 to 4): Gas heats in 40 to 50 minutes; electric takes 80 to 120 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.
Meaning for a family of 4, the daily usage of water is 900 l then they should opt for a water tank that has a capacity of 1350 liters or more.
Sediment build-up is one of the most common reasons for water heater failure. As sediment accumulates in your tank, your water may become discolored, and your unit becomes less efficient. There's also the significant risk of tank corrosion.
Common Causes of Hot Water Running Out Quickly
Hot water vanishing too soon? That usually comes down to a handful of culprits: tank size, sediment buildup, faulty heating parts, or a thermostat that's off.
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.
You can take several steps to improve heating efficiency and get hot water faster.
Newer models use advanced technology to heat water more efficiently. They convert more of the energy they consume into actual hot water instead of losing it as waste heat. This means you'll use less electricity or gas to get the same amount of hot water. The difference can be pretty dramatic.
Once your new water heater is installed, it's vital to follow the proper procedure before using it to prevent potential issues. The initial step after installation is to run the water for approximately 10-15 minutes.