Electric water heater for domestic hot water
Between the different solutions to obtain hot water in our home, be it for the kitchen or the bathroom, is to install a electric boiler for ACS (Also called electric boiler with some frequency in the Spanish of Mexico).
Actually, electric water heaters they were the first household appliances for heating domestic hot water, especially, the bathroom. With the evolution, they began to serve hot water in the kitchen, laundry room and with the appearance of new technologies, instantaneous electric heaters (Electric water heater) were introduced.
First, we must clarify … What is an electric water heater? Is a device that heats water by means of a resistance with electrical energy (without combustion) and stores it in a boiler or tank for later, distribute it around the house; bathroom, kitchen, laundry room, etc. Not to be confused with the electric heater, although many large surfaces include it with the same name, it is not the same.
The Electric heaters are evolution, and these they heat the water instantly, that is, as it enters through the pipe, they do not have an accumulator - water tank. But let's focus.
| DHW electric water heaters are ideal for |
| Homes that do not have a gas installation |
| For small studios or homes with few users |
| For second homes or homes for occasional use |
| When we need constant temperature, even though I varied the water flow |
With these concepts clear, we have to see the types of electric water heaters that we can buy in stores, characteristics, ranges and some useful tips.
What types of electric water heaters are there?
We always comment on it, we must know the options offered by the market to generate domestic hot water (DHW) but as we will see later, there are other factors that will determine what type of electric boiler we will buy.
There are three variants: vertical, horizontal and reversible, with different capacities to collect water depending on the manufacturer; 15, 30, 80, 50, 100, 200, 300 Liters.
1.- Vertical electric water heaters
They are those models that are embedded - embedded in the wall vertically. The full capacity of the pond is exploited with precise thermostat measurements in water temperatures and an optimization of the water stratification.
Vertical electric water heaters allow more capacity tanks than vertical ones, mainly due to their installation and remember that we are adding considerable weight to the wall (it is advisable to look for thick partitions, mainly 25 cm minimum)
2.- Horizontal electric water heaters
The horizontal models are designed to be installed above the door, in attics or in spaces where we have an obligation to install it horizontally. We must take into account the weight that the partition can support and the issue of plumbing, inlet and outlet of water that is not always possible.
3.- Reversible electric water heaters
These reversible models have the ability to be installed vertically or horizontally. Although they are versatile, from a technical perspective they have some shortcomings since it requires a certain configuration in the interior components.
For example: We cannot take advantage of the full capacity of the thermos (we lose 10% of the capacity of the boiler) and the possibility of erroneous measurements with the thermostat.
Besides, we have to know the parts of an electric water heater or we will not know what we are buying. This simple little schematic will help us get a general idea:
| Advantages | Drawbacks |
| Constant temperature | The cost of electricity can vary substantially |
| The temperature degrees are maintained with variable flow | The amount of water is limited |
| Gas hazards are avoided | Space is needed in its placement |
| Ease of installation | Has heat losses |
| It does not have a fixed minimum price like gas | Habits needed - discipline in your daily use |
Differences with a boiler, electric or gas heater, water storage tank and DHW heat pump
We add this section because sometimes many users look for one thing and it turns out that they need another, or that they have been advised badly. A brief review…
- Boiler: It is capable of producing hot water at a higher flow rate and feeds not only domestic hot water (DHW), but also the home heating installation (water radiators or underfloor heating at home)
- Electric heater: They heat the water instantly by means of electricity (not suitable for high water flows), they do not have an accumulator - water tank. Water heater or gas heater, the same, but it is fueled with gas and there is combustion, but they need a minimum of water pressure to "fire" (ignite).
- Water accumulators: Although the concept is very similar to the thermos, it is not the same. When we have an oil or gas boiler for heating only (See gas boilers and oil boilers), we can buy a water accumulator to obtain sanitary hot water (DHW for the bathroom and kitchen). The system to heat the water is by means of a coil connected to the boiler.
- Heat pump for DHW. Some call them the «electric water heaters with heat pump»Modern appliances, which, in reality, are like an air conditioner with a condenser coil inside the accumulator to produce DHW (domestic hot water). They use the heat of the air to heat the water (It is renewable energy and see aerothermal concept).
The ACS heat pump is very efficient from an energy saving perspective (with energy rating A) but much more expensive compared to traditional thermos models.
You have to do numbers to see if your purchase is profitable. Every year they are cheaper and more and more professionals recommend them (For their installation we need more space, they produce noise and it is recommended to install them indoors; garage, cleaning room, etc.).
How uniqueness and alternative, how the market adapts to demand, there are also hybrids that have the capabilities of an electric water heater and an accumulator.
Accumulators that also have an electrical resistance to avoid having to turn on the boiler in summer. A thermos has a resistance with high power and little insulation, on the other hand, an accumulator, the resistance is less powerful and has more insulation so that the heating is slower and more homogeneous.
Once we are clear about the differences, we continue to see which one we will need …
How to buy the most suitable electric water heater for home?
The electric water storage heaters with capabilities; 50, 100, 150 or 200 liters and more. It is chosen according to the number of people who will use it, the place of installation in the house, while the resistance and the anode depend on the type of water; aggressive or limestone. Here, there are three points that will determine the type that we are going to buy:
- The capacity of the deposit that we will need to supply the house
- The place where it will be installed
- THE type of water that enters the house (soft and hard or highly mineralized)
Our tips for choosing the best electric water heater are …
1.- What size do I need? Boiler capacity
To know the size in liter capacity that we need, we must recognize how much water is consumed in the home. We will have to see the habits and the people who live in the house to select the range of thermos according to dimensions.
More or less, all manufacturers have guidance tables that list the equipment of the home (sink, laundry room, washbasin, shower and bathtub), the number of people living in the house and daily needs. We can look at the following table:
2.- Where can I install it?
Before buying, it is important to know where we are going to locate the DHW heating appliance. For consistency, it should be near the bathroomIn other words, we do not want a decrease in the temperature of the water due to the route it takes in the pipes until it reaches the bathroom.
So the best solution to place the electric boiler is directly in the bathroom, place as close as possible to the point of use of hot water (It avoids loss of water temperature before the route through the pipes). Also, we need close a plug and a water outlet.
The best solution to place the electric boiler is directly in the bathroom, more efficiency and energy saving
The previous image reminds us of the safety measures in the placement near the bathtub and the sink. And we will need more space under the outlet of the tubes, for assembly access, maintenance and repair operations.
Areas with a possible opening to the outside in the open air, for example, a gallery, balcony, garage, energy efficiency will decrease since we will need more electrical energy to maintain the temperature "X" as it is a colder area (It is advisable to insulate the enclosure, as well as the hot and cold water pipes).
And if we place it outside, which there are devices, they are more expensive since it is necessary to cover the tank with a good thermal insulator (high-density polyurethane foam, etc.)
Once we are clear about the location, we will take the measurements of the hole and depending on the space we will acquire the appropriate one. As we mentioned at the beginning, the options are:
- Vertical: Some experts consider that it is the most recommended to better heat the water and obtain better performance in low consumption.
- Horizontal: We can place it in a mezzanine, above doors, install it on the false ceiling, on the wall or even on the floor.
- Reversible (multi-position): They are the versatile ones that can be placed both horizontally and vertically and remember that from a technical perspective, due to the arrangement of the components, they are not the best option.
3.- The type of water (hard or soft)
If we start from, the thermoses take the cold water from the supply network and heat it through an electrical resistance, then Why does lime damage electric water heaters?
The hardness of water drinking water that enters our home (calcium and magnesium concentrations) affects the resistance of an electric water heater and, therefore, the useful life of the appliance. The excess of lime prevents the correct transmission of heat (energy efficiency) of the water resistance.
Inside, there is also a magnesium anode (anti-corrosion protection of the boiler) is a protection mechanism for the tank due to excess lime. It is a magnesium-coated part that attracts lime to protect the deposit from corrosion. With harder guides, the "anode works harder" and more breakdowns or changes.
So we have two weak points in the internal mechanism:
| Walls cuba - boiler | Resistance that heats the water |
| It is protected with the magnesium anode (The bigger the better) | It is protected with a cover |
But… Why do some thermos last longer than others? To achieve a longer useful life, the resistance must have a sheath and the magnesium anode must be large. In cheap models, especially the magnesium anode is small, it "corrodes" earlier and its use is shortened.
With a larger magnesium anode the device will have a longer life
Although the newer models have anti-corrosion systems that guarantee the durability of the tank regardless of the characteristics of the water.
Even so, we must be aware of these discrepancies with reference to the type of resistance of the electric boiler:
- Sheathed ceramic heater (For hard or semi-hard water): It has a ceramic protection and better withstands the aggression of lime. Recommended in coastal areas and other places where the water has a lot of lime. Problem, it takes longer to heat the water because it is not in direct contact and the advantage, they last longer.
- Submerged armored resistance (For soft waters): Heats the water faster, but it is more sensitive to dissolved minerals in hard water, accelerating the corrosion of internal parts with the disadvantage that the useful life of the appliance is shortened.
The problem comes when we heat the water above 60ºC. When we raise the temperature of the water, the gases are less soluble, we favor the evaporation of CO2 and that is when the lime is deposited. The map of lime hardness in degrees for Spain:
4.- Other options and characteristics that we should look at
The mechanism and other internal parts of the electric water heaters It should also influence our final purchase decision, which will influence its durability and consumption. We are going to see some tips and factors that we should review:
- Tank lining
We need it to be more or less resistant to lime and corrosion, in this sense, the vitrified - vitroceramic coating is one of the best options for any appliance, and, more so, if we talk about hard water.
- Adequate insulation in the tank
The objective, keep the water hot for longer inside the boiler. We need less heat loss and greater energy savings, we will improve with an adequate thickness of the profile and without thermal bridges, achieving low-consumption, more compact and efficient electric water heaters.
- The power of the thermos
If we want to heat the water faster, we will need more power, but also the electrical consumption will be higher (Power 875w, 1,200w, 1,500w, 1,750w, etc). Keep in mind that higher power means less useful life due to greater wear on its parts.
With a temperature - from time to time - of 45ºC (it is not necessary the usual 60ºC) it is enough to guarantee hot water and less electricity consumption
- The digital programmer
For comfort and good sense in saving energy, apart from having a temperature setting, we will need them to have a thermostat (time programmer - more information in this article about heating thermostats) with the possibility of programming the time bands according to our daily uses. It is called programmable electric water heater.
For example, if we shower in the morning, we can program it to have hot water using electricity from the reduced rate at night. Many models are already programmable electric water heaters, the most innovative and modern have a mobile app.
A programmable thermos can save up to 20% on the electricity bill
- The energy label
By now more or less we are all aware of what the energy labels mean on the home appliances, heating appliances and low consumption electric water heatersor. They indicate the energy classification and the greener (Class A) the better, the worse, the C.
The applicable regulations for electric water heaters It is the European Directive of Ecodesign ErP (Energy Related Products) and the energy labeling ELD (Energy Labeling Directive) we can consult from HERE. Also the IDAE has an interesting guide.
- Installation
Be careful with the theme of the facilities and their design. For advice and security, go directly to a professional and always ask when we buy the electric water heater how much the installation costs. Sometimes the offers for sale are tight and the price is passed on to the work of the installer.
When we buy the electric water heater, ask how much the installation costs and guarantees
- Must make sure that a safety valve is placed to control the pressure of the water heater. An example of how an installation would look to have domestic hot water at home would be:
- Always look at the manufacturer's instructions and this installer's guide (It is more for professionals) and the HE Energy Saving Technical Code.
- It cannot be installed on top of or near another heat source.
- It should not be installed in places with ambient temperatures below 0 ºC.
- Install it in a place that allows handling, maintenance and removal of the magnesium anode.
- Do not buy second-hand (they are all problems in the long run), buy new thermos with a guarantee.
- Look at electrical power installed at home, we still need more.
Obviously, all these factors that we have discussed will affect the final purchase price for the best electric water heaters. The excellent materials, technological capabilities and insulating tightness ability, the more expensive it will sell.
Electric water heater prices, brands and where to buy the appliance
As we have seen, the price of an electric water heater It depends on many factors, but without a doubt, you have to look for quality if you want the glove years installation without problems. On average, we could say that the prices of electric water heaters are around:
| Electric thermos prices | |
| Thermoelectric capacity | Average price in euros |
| 80 liters of water for 2 people | 180 Euros |
| 100 liters of water for 3 people | 250 Euros |
| 150 liters of water for 4 people | 290 Euros |
| 200 liters of water for 6 people | More than 400 Euros |
The values shown are an average with average qualities for Spain. It must be taken into account that when we exceed the range in storage with more than 150 liters of capacity, they become more expensive because they enter a unique range.
Remember the theme of the installation. Normally it is a separate price, but with an offer it can be free.
What trademarks recognized in the sector could be: Cointra, Vaillant, Ariston, Teak, Bosch, Tesy, etc there is an extensive range! That you should always compare prices and offers, from neighborhood stores to large stores such as Carrefour, Leroy Melin, Bricomart, Bricodepot, or on the internet, starting with the Amazon that has interesting offers and other websites on the subject.
Tips to use consistently
First we must recognize where we use more hot water and thus, we will understand, where is the energy expenditure. An electric water heater for shower, sink, washbasin uses on average …
- In long periods of time when we do not use hot water (for example, single-family homes or second homes) we must empty the tank.
- They cannot be on all day. Use the daily programmer (thermostat) to set an on and off time range.
- Change daily habits and shower the family, more or less, the same time slot We will save a lot of electricity!
- Long baths should be avoided and hot water used consistently.
- See the possibilities of hourly electricity rates with cheaper prices.
- If they are on a balcony or gallery, especially in winter, the pipes can be covered with some insulating material.
See for more information our complete article with 30 tips on how to save energy in the home.
Although the manuals of these equipment to produce domestic hot water there are recommendations and solutions to possible problems of use or wear of the device. We add a summary scheme that links problem - description - and possible solution in its operation:
It is a device that should last us many years, therefore, the cheap electric water heaters they are not the option. It is worth making an initial investment, to have a device with a long useful life and avoid future repairs.
Buy better specialized brands: Junkers thermos, Vaillant, Cointra, Tesy, Thermor, Tasting, Ariston, etc, with facilities in warranties and good technical service (Always ask for warranty in years and parts).
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