How Long Does A Water Heater Take To Heat Up?

Whether you are considering purchasing a new water heater, are dealing with an old water heater that’s no longer up to snuff, or you’re just the curious type in general, you may well wonder how long it takes for a water heater to heat up a full tank of water.

How Long Does it Take for a Water Heater to Heat Water?

The answer to the question of how long for a water heater to work depends on what type of water heater we’re dealing with.

Standard “Tank Storage” Water Heater – Natural Gas Powered

How long does it take for a gas-powered water heater to heat up water? A. O. Smith says a 40 to 50 gallon gas tank fully recovers in about 30 to 40 minutes, depending on the size of the tank and how cold the water is initially.

Standard “Tank Storage” Water Heater – Electric Powered

How long does it take for an electric-powered water heater to heat up water? A. O. Smith says a 40 to 50 gallon electric tank takes 60 to 90 minutes, again depending on the size of the tank and how cold the water is initially.

Tankless Water Heaters – Gas or Electric

How long does it take for a tankless water heater to heat up water? Regardless of whether it is gas or electric-powered, a tankless water heater is “on demand,” meaning it will heat up the water immediately and keep a flow of hot water coming as long as you need.

Since a tankless water heater only heats the water you need and does not have to maintain heat in a large storage tank, they can use less energy. The U.S. Department of Energy estimates that a gas tankless heater saves about a third on water heating for typical use, and real savings vary with how much hot water you use.

I should mention that if you have a conventional tank storage system, either gas or electric, the above times are for heating the entire tank of water – that is, the first time you use it, or if you’ve used all of the hot water in the tank and it needs to recover and reheat.

If you are just turning on the tap, though, and the tank is already full of hot water, it too is essentially “on demand,” and if your pipes are reasonably well insulated and the tank is not too far away you will have hot water pretty much instantly.

Why Is My Water Heater Taking So Long to Heat Up?

If you’ve found my article, chances are that you are probably wondering not just how long it takes for a hot water heater to work, but why yours is taking so long to heat.

There are many different reasons a water heater is not working as well as it might – not just taking too long, but also maybe not reaching satisfying temperatures even after a long time.

Of course, if your water heater is not working at all, you should:

• Check the pilot light and have a professional check the gas supply (for gas-powered water heaters)
• Check the electric supply, or call an electrician, (for electric heaters), making sure it is connected and the circuit breaker has not tripped
• Also for electric heaters, you may need to reset the thermostat

To be as clear as possible, you should not check or work on gas lines or electricity yourself – it can be extremely dangerous, even deadly, and it can also violate building codes and compromise the value of your home. Always use a qualified and licensed professional for any gas line or electrical work!

If these things don’t work, or if your heater is working but just very slowly, or not getting hot enough, the problem might be:

• Your tank is too small for your home and family and your daily use
• Your heater is too far away from your usage points
• Your pipes are not adequately insulated
• The tank may need to be flushed

These are common issues, but the most common issue seems to be that your water heater is simply on its way out – either it has reached the end of its lifespan, or it has problems that may not make it worth fixing. If so, you might need to have it serviced or even just replace it.

If your water heater is too old – that is, 8-12 years or so, it may have problems that need repair, you may not want to spend, or even waste, your time and money on maintenance, repair, plumbing work, and other pursuits, when a new, high-efficiency water heater can lower your running costs.

📍 Recommended Reading: How Long Do Water Heaters Last

This is not a buyer’s guide, but it might be helpful if I list out here my favorite hot water heaters – if you do need to replace your old unit, you might as well get one that will work not just quickly, but efficiently, affordably, reliably and for as long as possible – and provide the most satisfying experience each and every time.

So I will include my personal recommendations for the best hot water heater you can get, including a pick for gas-powered and electric-powered in the conventional tank storage category and both gas and electric picks for tankless water heaters as well.

Best Electric Water Heater: Bosch Tronic 5000 T 40-Gallon Standard Electric

What I Like:

• Very well built and long-lasting
• Super efficient
• Corrosion-free design
• Pre-installed water connectors
• Great Warranty

Drawbacks:

• A bit expensive – though IMO well worth it!
• Bosch lists the Tronic 5000 T on its discontinued products page, so this is remaining stock (the listing was live on 21 Oct 2026)

Second Best: Stiebel Eltron Tempra 29 Plus Tankless Electric Water Heater

What I Like:

• Lowest running costs
• Great for the environment
• Two temperature memory presets
• Low maintenance
• Very high material and build quality
• High volume continuous hot water flow

Drawbacks:

• Needs three 40-amp breakers and a minimum 200-amp service, so budget for a licensed electrician

The Best Gas Water Heaters

Gas is the main water heater fuel in about 48% of U.S. homes, just ahead of electricity at about 46%, according to the U.S. Energy Information Administration’s 2020 survey. Whether gas costs less to run depends on local gas and electricity prices. Gas tanks heat and reheat faster, and gas is a good choice if you already have the gas lines. Not every gas model works in a power outage: A. O. Smith’s electronic-ignition models, for example, need a 120-volt outlet, so check yours.

Best Tankless Natural Gas Water Heater: Rinnai V53DeN Natural Gas Tankless Hot

What I Like:

• Strong hot water flow
• Can supply a small home from one unit (Rinnai lists up to 5.3 GPM)
• Easy outdoor installation
• Low maintenance
• Extremely well-made and reliable
• Great company

Drawbacks:

• Not enough volume for larger homes – see Rinnai RU130eN Tankless Natural Gas Water Heater