Electric water heaters; Types, characteristics, and buying tips. Which you need?

Electric water heater for domestic hot water

Among the different solutions to obtain hot water in our home, whether for the kitchen or the bathroom, is to install an electric water heater for DHW (Also frequently called electric boiler).

In fact, electric water heaters were the first domestic appliances to heat running sanitary water DHW, especially for the bathroom and kitchen. But first, we need to clarify a topic…

What is an electric water heater?

It is a device that heats water through a resistance with electrical energy (without combustion) and stores it in a tank or cylinder to later distribute it throughout the home; bathroom, kitchen, laundry room, etc. But… When is it better to install them?

🟧 Note: Do not confuse with instant electric heaters, these heat the water instantly, that is, as it enters through the pipe, they do not have an accumulator – water tank.

Having these concepts clear, it’s time to see the types of electric boilers that we can buy in stores, features, ranges, and some useful tips.

What types of electric water heaters are there?

We always mention it, you need to know the options the market offers 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 water storage capacities depending on the manufacturer; 15, 30, 80, 50, 100, 200, 300 Liters.

1.- Vertical electric water heaters

These are models that are embedded – recessed in the wall vertically. The full capacity of the tank is utilized with precise thermostat measurements in water temperatures and optimization of water stratification.

🟧 Tip: Vertical electric water heaters allow for larger capacity tanks. It is recommended to look for thick walls mainly of at least 25 cm for installation.

2.- Horizontal electric water heaters

Horizontal models usually have a smaller capacity than vertical ones, as their installation on the wall is more complex and requires greater support. You must consider the weight that the wall can support and the plumbing issue, water inlet and outlet, which 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 as they require a specific configuration in the internal components.

In a versatile model, we cannot take full advantage of the heater’s capacity (we lose 10% of the tank’s capacity) and there is a possibility of incorrect thermostat measurements

Additionally, we need to know the parts of an electric water heater or we won’t know what we are buying. This simple small diagram will help us get a general idea:

Differences with a boiler, electric or gas heater, water accumulator, and DHW heat pump

We add this section because sometimes many users look for one thing and it turns out they need another, or they have been advised incorrectly. 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’s heating system (Water radiators or the underfloor heating)
• Electric water heater: Heats water instantly through electricity (not suitable for high water flows), does not have an accumulator – water tank. Gas geyser or heater, the same, but it is powered by gas and there is combustion, but they need a minimum water pressure to “trigger” (turn on).
• Water accumulators: Although the concept is very similar to the heater, it is not the same. When we have an oil or gas boiler only for heating (See gas boilers and oil boiler), we can buy a water accumulator to obtain domestic hot water (DHW for the bathroom and kitchen). The system for heating the water is through a coil connected to the boiler.

• Heat pump for DHW. Some call them “electric water heaters with heat pump” modern devices, which, in reality, is like an air conditioner with a condenser coil inside the accumulator to produce DHW (Domestic hot water). They use the heat from the air to heat the water (It is renewable energy and see aerothermal concept).

🟧 Note: The heat pump for DHW is very efficient from an energy-saving perspective (with energy rating A) but much more expensive compared to traditional heater models.

As a singularity and alternative, as 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 electric resistance so as not to have to turn on the boiler in summer. A heater has a high-power resistance and little insulation, whereas an accumulator, the resistance is less powerful and has greater insulation for slower and more homogeneous heating.

Now having the differences clear, we continue to see which one we will need…

How to buy the most suitable electric water heater for home?

The electric water heaters with water storage with capacities; 50, 100, 150, or 200 liters and more. It is chosen based on 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 calcareous. Here, there are three points that will determine the type we are going to buy:

• The capacity of the tank we will need to supply the home
• The place where it will be installed
• The type of water entering the house (soft and hard or highly mineralized)

Our tips for choosing the best electric water heater are…

1.- What size do I need? Tank capacity 

To know the size in liters 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 living in the home to select the heater range according to dimensions.

More or less, all manufacturers have indicative tables that relate the equipment of the home (sink, laundry, 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 place the device to heat DHW. For coherence, it should be close to the bathroom, that is, we do not want a decrease in water temperature due to the path it takes in the pipes until it reaches the bathroom.

So the best solution to place the electric boiler is directly in the bathroom, the closest possible place to the hot water usage point (Avoids water temperature losses due to the path through the pipes). Also, we need nearby a plug and a water connection.

The best solution to place the electric boiler is directly in the bathroom, more efficiency and energy savings

The previous image reminds us of the safety measures in placement near the bathtub and sink. And we will need more space below the tube outlets, 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, will decrease energy efficiency as we will need more electrical energy to maintain the temperature “X” as it is a colder area (Advisable to insulate the envelope, as well as the cold and hot water pipe).

And if we place it outside, there are devices, they are more expensive as they need to cover the tank with good thermal insulation (High-density polyurethane foam, etc)

Once we have the location clear, we will take the measurements of the space and based on the space we will acquire the appropriate one. As we mentioned at the beginning, the options are:

• Vertical: Some experts consider it the most recommended to heat water better and obtain better performance in low consumption.
• Horizontal: We can place it in a loft, above doors, install it in the false ceiling, on the wall, or even on the floor.
• Reversible (multiposition): They are the versatile ones that can be placed both horizontally and vertically and remember, 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 heaters take cold water from the supply network and heat it through an electric resistance, then why does lime damage electric water heaters?

The hardness of the potable water entering our home (concentrations of calcium and magnesium) affects the resistance of an electric water heater and, therefore, the useful life of the device. Excess lime prevents the correct transmission of heat (energy efficiency) from the resistance to the water.

Inside, there is also a magnesium anode (anti-corrosion protection of the tank) it is a protection mechanism for the tank due to excess lime. It is a piece coated with magnesium that attracts lime to protect the tank from corrosion. In harder waters, the “anode works more” and more breakdowns or changes.

So we have two weak points in the internal mechanism:

But… why do some heaters last longer than others? To achieve a longer useful life, the resistance must have a cover and the magnesium anode must be large. In cheap models, especially the magnesium anode is small, “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 allow guaranteeing the durability of the tank regardless of the water characteristics.

Even so, we must know these discrepancies regarding the type of resistance of the electric water heater:

• Ceramic sheathed resistance (For hard or semi-hard waters): 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 is more sensitive to dissolved minerals in hard waters accelerating the corrosion of internal parts with the disadvantage that the useful life of the device decreases.

The problem comes when we heat the water above 60ºC. When we raise the water temperature, gases are less soluble, we favor the evaporation of CO2 and then lime is deposited. The map of lime hardness in degrees for Spain:

4.- Other options and features we should look at

The mechanism and other internal parts of the electric water heaters should also influence our final purchase decision as they will affect their durability and consumption. Let’s see some tips and factors we should review:

– Tank coating

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, if we talk about hard waters.

– Adequate insulation in the tank

The goal, keep the water hot for longer inside the tank. 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 electric water heaters, more compact and efficient.

– The power of the heater

If we want to heat the water faster, we will need more power, but also the electrical consumption will be higher (Powers 875w, 1,200w, 1,500w, 1,750w, etc). Keep in mind that, more power is less useful life due to greater wear of its parts.

With a temperature – occasionally – of 45ºC (60ºC is not necessary) it is enough to guarantee hot water and less electrical consumption

– The digital programmer

For convenience and sensibility in energy savings, apart from having a temperature adjustment, we will need them to have a thermostat (time programmer – more information in this article about thermostats for heating) with possibilities to program time slots according to our daily uses. It is called a programmable electric water heater.

For example, if we shower in the mornings, we can program it to have hot water using the reduced night rate electricity. Many models are already programmable electric water heaters, the most innovative and modern have a mobile App.

A programmable heater can save up to 20% on the electricity bill

– The energy label

At this point, more or less, we all have an awareness of what energy labels mean on appliances, heating devices, and low-consumption electric water heaters. They indicate the energy classification and the greener (Classification A) the better, the worst, the G.

In the characteristics of a heater with letter C or B on the label, it is the most coherent and normal in relation to quality price. Those with letter B and A are expensive although they consume less and are more intended for large tanks (120 l, 150l, 200l).

The applicable regulation for electric water heaters is the European Ecodesign Directive ErP (Energy Related Products) and the energy labeling ELD (Energy Labelling Directive) we can consult from HERE. Also, the IDAE has an interesting guide.

– The installation

Be careful with the issue of installations and their design. For advice and safety, directly go to a professional and always ask when we buy the electric water heater how much the installation costs. Sometimes the sales offers are tight and the price is reflected in the installer’s work.

when we buy the electric water heater, ask how much the installation and warranty cost

• You must ensure that a safety valve is placed to control the pressure of the 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 guide (It is more for professionals) and the HE Energy Saving of Technical Code.
• It cannot be installed above 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 heaters with a warranty.
• Check the installed electrical power at home, we may need more.

Obviously, all these factors we have mentioned will affect the final purchase price of the best electric water heaters. With excellent materials, technological capabilities, and insulating tightness capacity, it will be sold more expensively.

Electric water heater prices, brands, and where to buy the device

As we have seen, the price of an electric water heater depends on many factors, but without a doubt, you have to look for quality if we want the installation to last for years without problems. On average, we could say that the prices of electric water heaters are around:

The values presented are an average with medium qualities for Spain. Keep in mind that when we exceed the range in the tank with more than 150 Liters of capacity, they become more expensive as they enter a unique range.

Remember the installation issue. Normally it is a separate price, but with some offers, it can be free.

As brands recognized in the sector could be: Cointra, Vaillant, Junkers, Ariston, Teka, Bosch, Tesy, etc. There is an extensive range! You should always compare prices and offers, from neighborhood stores to large surfaces like Carrefour, Leroy Merlin, Bricomart, Bricodepot, or on the internet, starting with Amazon which has interesting offers and other thematic websites.

We recommend buying the following electric water heaters for their coherence in price quality:

• COINTRA electric water heater of 100 liters, with 1500w and letter “C” in efficiency. For a household of 3 people more than enough. Hot water for two showers (17 l/min). You can see it on the official Cointra page from HERE.
• In Bricomart they have good offers from the Teka brand. Both 80L and 100L and at very competitive prices with energy rating “B”. An example is this device of eighty liters and 1500w.
• The next one is from the Ferroli brand. With 90 liters, 1,800 w, and with a digital thermostat. With letter “B” you can see it at Bauhaus from HERE.

Summary videos

A brief summary of what you should know before buying an electric water heater:

Usage tips with coherence

First, we must recognize where we use more hot water and thus, we will understand, where the energy expenditure is. An electric water heater for shower, sink, washbasin uses on average…

• In long periods that we do not use hot water (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 a time range for turning on and off.
• Change daily habits and shower the family, more or less, at the same time slot. We will save a lot of electricity!
• Avoid prolonged baths and use hot water with coherence.
• 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 at home.

Although the manuals of these devices to produce domestic hot water have recommendations and solutions to possible usage or wear problems of the device. We add a summary diagram that links problem – description – and possible solution in its operation:

It is a device that should last us many years, therefore, cheap electric water heaters 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 heaters, Vaillant, Cointra, Tesy, Thermor, Cata, Ariston, etc, with facilities in warranties and good technical service (Always ask for warranty in years and parts).

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