Picture the scene: you’ve gotten the kids up, ushered them into the shower and to the breakfast table with just enough time to spare for your own morning ablutions then, horror of horrors, you find there’s no hot water in the shower. You may be asking yourself “why is my shower cold” or, more importantly, “how long does it take for hot water to come back?” The answer to these questions, and so many others in the home is, it depends.
Understanding Your Water Heating System
There are several types of common water heating systems in our homes, and the details of how long your hot water will take to come back will vary slightly depending on which you happen to have.
There are lots of models and permutations of the water heater in American homes, but the two key differences are:
Tanked:
Slightly old fashioned but still the most common in American homes, a conventional water heater consists of a large insulated tank (typically 30-80 gallons) which holds hot water. They’re cheap to purchase and easy to maintain but generally not very energy efficient for most households
Tankless:
More modern and slowly gaining prominence, tankless water heaters supply hot water on demand. They take up less room than tanked heaters and generally more energy efficient but they’re much more expensive to install and require more maintenance.
On top of these two general descriptors, we also have solar systems (which use panels installed on the roof to directly heat water using the sun) and even hybrid varieties which combine either a heat-pump or solar system with a conventional fuel source.
If yours isn’t powered via a renewable source or by a heat-pump, it will either be powered by an electric element or a gas burner.
How Water Heaters Work
At their core, all water heaters serve a single purpose and the clue really is in the name: they heat water for domestic use. The mechanics of how they do this vary from type to type, largely based on which fuel they use.
Electrically powered water heaters use an element, much like those found in an electric kettle, to heat up your water. These are most commonly tanked systems, though on-demand systems do exist and most electric showers work this way.
Gas powered ones heat water by directly burning gas. This could be tanked or tankless as is the case in a modern combi-boiler.
Whichever you have, the time it takes for the water to heat up is called the recovery time. Typically, for on-demand systems, this is in the seconds but for storage systems it will be significantly longer.
Factors Affecting The Recovery Rate
Regardless of which type of water heating system is installed in your home, how long it takes for hot water to come back will vary depending on a few factors: capacity, energy source, initial temperature and thermostat settings.
Let’s look at each in turn:
Capacity
It’s a simple fact of life that bigger tasks take longer and heating water is no different. A 50 gallon tank will take longer to get up to the desired temperature than a 25 gallon one and an 80 gallon one will take even longer.
Even with a larger element or burner running hotter, there’s a sliding scale of efficiency.
In comparison, because a tankless system is heating a relatively small volume of water at any given moment (usually around 3.5 gallons per minute or slightly more if you’re running multiple faucets), they can work almost instantaneously to offer an on-demand flow of hot water.
Energy Source
Which fuel your system uses will also play a significant role in determining how long the hot water takes to come back once depleted.
As a general rule, a gas water heater will take around an hour to refresh a 40 gallon tank, where as an electric heater will require about an hour and a half to two hours to get up to temperature. Because solar systems tend to work gradually through the day and are usually connected to an electric back-up system, they usually have about the same refresh rate.
Why is gas so much quicker? Gas burners can generally run at a hotter temperature than can be efficiently generated by an electric element big enough to heat a whole tank.
Initial Water Temperature
It shouldn’t come as much surprise to find that the lower the temperature the water starts at, the longer it will take to heat up to your desired level.
Whatever system type you have installed in your home, the temperature of the water from your mainline will have at least some effect on your refresh rate. If you’ve ever enjoyed a glass of ‘winter water’ early in the morning, you’ll know that this can vary from season to season.
Thermostat Settings
All hot water systems rely on a thermostat to control how hot they make the water. Unsurprisingly, the hotter the thermostat is set, the longer it will take to heat the water to that level.
Likewise, setting a lower temperature on your water heater’s thermostat will mean that your recovery time is also lower, though the water won’t be as hot.
Average Recovery Times
As we’ve already covered, there’s a wide range of factors which influence how long it takes for your hot water to come back once it’s been used but a very rough guide by system type might be something like:
- Gas Powered Conventional Tanked System: around an hour for a 30-40 gallon tank
- Electric Powered Conventional Tanked System: Around 80 minutes to two hours for a 40 gallon tank
Tankless Systems
Tankless systems usually have an effectively instantaneous recovery rate as water is heated as it flows through. It may take a few seconds to displace water which has cooled in your pipes but to all intents and purposes (and certainly in relation to waiting for a tank to heat up), it’s pretty much instant.
Solar And Hybrid Systems
It’s harder to put a number on a renewable system like solar water heaters because they will vary depending on the time of year and whether they have a ‘boost’ feature powered by electricity.
In general, solar and heat-pump systems are more efficient in the summer (when there is more sunlight and ambient heat to harness) and take longer to recover in the winter. Electric boosts will generally follow the basic rules of any other tanked electric system.
Enhancing Your Hot Water System’s Efficiency
If you’re looking to keep your recovery rates down as much as possible, there are certain steps you can take to ensure your system, regardless of which type you have, is as efficient as possible:
Regular Maintenance:
Keeping things clean and in working order can work wonders. Regularly flushing tanks and checking anode rods and repairing or replacing components as needed will ensure your water heater is working at full capacity.
Upgrading Insulation:
heating anything is always a battle between the source of heat and the ambient temperature. Boosting your insulation (especially on a tanked system) by adding a jacket will keep your water hotter for longer and offer a slight boost to recovery times.
Upgrading Your System:
unsurprisingly, the technology underpinning our water heaters continues to evolve. Newer systems are constantly being developed offering greater energy efficiency and quicker recovery times.
Trouble Shooting Common Issues
The two most common issues when it comes to how long your hot water takes to come back are it taking too much time or the temperature fluctuating wildly during use.
In the case of a delay to recovery time, the most likely culprit is a sediment build up. It’s a relatively simple procedure to flush your tank and get rid of that nasty gunk which is cutting efficiency.
In the case of water that unexpectedly goes from hot to cold and back again, the problem could be more serious and require professional repair or a full replacement. Alternatively, it could be an issue with your pressure balancing valve.
When To Seek Professional Help
If you feel that how long your hot water is taking to come back is a problem, or if you notice a significant change in recovery times, it’s often best to enlist the services of a professional plumber. They will be able to advise on the causes and the potential options for solutions.
While you may be able to undertake some tasks (like flushing the tank) yourself, anything that involves dealing with gas or electrical wiring is best left to those who know what they’re doing- indeed, it may be required by local regulations.
So, how long does it take for hot water to come back when the stored supply has been exhausted? The answer is: it really depends.