I have recently been doing some pretty intense study into Electric Tankless Water Heaters. I did a 2 part series about Tankless Water Heaters in normal a while back, but I didn't talk much about Electric tankless except to say that they don't seem to make much sense.
Well, at the risk of manufacture all the Electric tankless manufacturers mad, what I found out in my study just confirmed that they legitimately don't make much sense. I just have more information now as to why not. Since tankless water heaters are being marketed so heavily right now, I wanted to give you the lowest line on what the marketing may not tell you. Then at least you will be able to make an informed decision if you are considering tankless.
ELECTRIC
Tankless Basics
First of all, it is important to understand the basic operation of a tankless water heater. All tankless heaters, either electric or gas, use the same basic process to heat water.
1)When a hot water faucet is opened this causes water to flow straight through the tankless unit.
2) When the volume of flow is adequate to trigger the unit to come on it begins heating water.
3)The whole of water that the heater allows to flow straight through is regulated by the desired outlet temperature.
4)This is, in turn, affected by the climatic characteristic of the incoming water. The colder the incoming water the more heat the heater has to create.
Temperature Rise and Gallons Per Minute
That's why the operation of tankless water heaters is measured by how many gallons per little (Gpm) the heater will deliver at a desired climatic characteristic Rise. The greater the desired climatic characteristic Rise, the less Gallons per little of hot water can be produced.
How many Gpm a tankless heater can deliver is entirely dependent on how much vigor (either electric or gas) the unit has ready to heat the water. If you want more hot water you have to use more energy. In a gas tankless this means more Btus. In an electric tankless this means more kilowatts, which also means a bigger amperage draw. There is no way to get nearby this, it's just the way it is.
Electric vs. Gas
Since we are talking about electric tankless, the only thing I will say about gas models is that they roughly all the time have good operation than electric models. The "largest" electric tankless heaters can't match the production of a "standard" gas tankless unit. For the record, "regular", tank type water heaters have the same differences. Gas units just heat water faster than electric, tankless or otherwise.
How Much Hot Water Is Enough?
Now that you know the basic concepts, here's why I don't think an electric tankless is a good idea:
The largest unit I could find is only capable of delivering nearby 5 Gpm (gallons per minute) at a modest 50° climatic characteristic rise. At a 60° rise this drops to 4.3 Gpm. By the way, the only habitancy I know who propose using a 50° climatic characteristic rise when sizing a heater are the tankless manufacturers themselves. Every plumber I know uses 60° as a minimum, real world figure. other thing to keep in mind: the Plumbing Code requires "hot water" to all fixtures for "bathing, washing, culinary purposes...etc. The Code defines "hot water" as "greater than or equal to 110° F".
Ok, if all of these numbers are manufacture your head hurt here's the lowest line. A proper shower head uses at least 2.5 Gpm (gallons per minute). The biggest residential electric tankless can deliver less than 5 Gpm at a realistic climatic characteristic rise. That means if two shower heads are running at once they will have less than full flow. Since one of the most common complaints I hear is that the showers don't have adequate pressure already, this is just a formula for dissatisfaction.
But that's not all. This lackluster operation comes with a price.
How Much Electricity Is Enough?
Electric tankless water heaters wish an large whole of electricity as compared to any other tool in the home. The largest models wish a whopping 160 amps. With most new homes having a 200 amp electrical service, that's 80% of the total electrical capacity of the home. Many older homes don't even have a large adequate electrical assistance to power the tankless, much less the rest of the house.
In case you think I'm just ranting, I'm not alone. Electric Utilities hate electric tankless water heaters. Since they make money selling electricity you would think they would love them. It seems that they use so much power that they can overload the system. Check out this citation from one power company's website on tankless:
"o The new load of a tankless water heater can sometimes equal the load of an entire new home!
o ...if a buyer installs a tankless water heater, the increased electric ask may exceed the found specifications of the principles and wish an upgrade of the cable and transformer. ... Will be charged directly to the customer. & If a buyer installs a tankless water heater, the buyer is required by stylish tariff in both the Carolinas and Florida to pay the full cost to upgrade their facilities (including cable and transformer) to meet the need.
o Customers complaining about a voltage fluctuation or flickering lights may be seeing the impact of a tankless water heater in their neighborhood. It is important to note that this voltage fluctuation may be noticed by other customers in expanding to the buyer with the tankless water heater - since any customers often share a singular transformer. An investigation of all customers on the transformer may be important to decide the source of the problem. If voltage problems exist because of a tankless water heater and a installation upgrade is necessary, the buyer with the tankless water heater is required to pay the full cost to upgrade prior to construction."
I don't know if this is legitimately enforced but it is pretty plain to see that this Power business is certainly trying to discourage the use of electric tankless water heaters.
Look, I do not have an axe to grind against the electric tankless industry. There are even a few situations where a small electric tankless might make sense. I just don't think they are a good selection for a whole house water heater. I also want to make sure that you can count on me to give you the real, no hype truth. And, in this case, I think electric tankless water heaters are a bad selection in most cases.
electric Tankless Water Heaters - The Shocking Truth ELECTRIC
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