Lately, tankless water heaters have gained a ton of popularity since they are considered to be more energy efficient and cost-effective in comparison to the old type of water heater units. However, you might wonder and ask “How are such advantages possible if they actually cost more in the market?” Also, another question you might have in mind once you decide to buy one is “What size tankless water heater do I need?” That is where we will help you figure in this article.
Why are Tankless Water Heaters Better than Tank Water Heaters?
A tank water heater can only preheat a set volume of water in its tank. Of course, you can choose to buy a bigger tank, but it will cost a lot more. So, when all the hot water gets used up in the tank, you’ll have to wait for it to refill and reheat to get hot water again. Tankless heaters, on the other hand, provide hot water as and when you need it. You simply need to turn on the faucet, and you will get a steady stream of hot water.
In terms of efficiency, a tank heater will operate continuously. This means it works even when you don’t need it. That is a whole lot of wasted energy that you are paying for. A tankless water heater is designed to increase the temperature of water only when you need it. It is a far smaller and compact system that basically flash heats the water when you turn your faucet on.
When it comes to the cost of the tank and tankless water heaters, the former is indeed cheaper than the latter. However, tank water heaters work out to be expensive as you use it and even wear out soon. Tankless water heaters will make a substantial difference on your electricity bills. They are known to reduce energy bill costs by more than 60%.
These are just a few of the top reasons why a tankless water heater is a significantly better choice between the two. Now that you are well informed about it, let us guide you on what is the right size tank for you.
What Size Tankless Water Heater Do I Need?
You will notice that any kind of tankless water heater will be rated on the basis of the maximum temperature rise that is possible at one given flow rate. Hence, to know what size is appropriate for you, you will need to determine what flow rate and temperature you require and for what, that is, if you want it for the whole house or if you want it in just one bathroom. It is important though that you don’t cut costs by choosing a smaller sized tankless water heater.
- Step 1
When it comes to flow rates, there are a ton of questions in people’s minds. Some of them include, at one time how much hot water will I need? Can I even run two showers simultaneously? Or can I run a shower and a sink or two together? To simplify things for you, we will talk about what the average flow rate gpm for each fixture is.
A tub would ideally have an average water flow of four gpm. A shower will have between 2.5 and three gpm. A washing machine would have an average water flow of two gpm. On the other hand, a dishwasher and the kitchen sink would have an average water flow of 1.5 gpm.
With that in mind, you will need to determine how many devices will need the tankless water heater and what the total flow rate of all of them would be. Add all the flow rates up in gallons per minute (gpm). This will be the flow rate that you will need from your heater.
To give you an example, if you want to use a water faucet and a shower head together, they should have a gpm rate of 0.75 and 2.5, respectively. This means you will need at least 3.25 gpm of water flow. You can reduce the flow rates by installing water fixtures that have low flow.
- Step 2
In this step, you will need to determine the necessary temperature rise. In order to do so, just subtract the incoming temperature of the water from the temperature that you desire. Unless you know the exact number, the temperature is typically around 50°F. In most cases, you will need your water temperature to be around 105°F to 115°F. That means you would need your water heater to provide you with a temperature rise of 55°F.
Let us give you an example of finding the right size. An average shower temperature will be anywhere between 105°F to 110°F, and it will use about 2.5 gallons of water. Now, if we assume that the water coming into the house is at 40°F and you want enough hot water to run two showers simultaneously, you will need the temperature rise of at least 65°F that provides you with 5gpm.
So, What Size is Ideal?
While choosing the right size of water heater entirely depends on you, in most cases, having a unit that would provide you with about four to five gpm is great for anyone who lives in a home with one bathroom. If you have a home with two bathrooms, then you should opt for a water heater that provides you with six to eight gpm. Having these will easily serve two to three applications simultaneously.
On the other hand, if you live in a large house with three bedrooms or more, then it is best that you install multiple tankless water heater units in your house. More rooms mean more people in the house and more need of hot water. A single heater would definitely not suffice in such cases.
We hope that this short article has provided you with necessary information on your question “What size tankless water heater do I need?” Although we have given you a rough idea on what ideal tank size you would need, it is best that you first calculate the amount of hot water you would need and how much gallons of hot water per minute you need too. Knowing those exactly will easily help you determine what size will suit you best.
You might like this: Rinnai RUC98iN Ultra Series Natural Gas Tankless Water Heater Review