How to Choose a Buderus Logamax Electric Boiler – What to Focus On

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How to choose an electric boiler Buderus Logamax – what to focus on

Electric boilers Buderus Logamax series E213 are among the most popular electric boilers on the Slovak market today. This is no coincidence – they combine compact dimensions, reliable German engineering, and a reasonable price. Despite this, in practice, I often encounter customers who choose the wrong power, ignore electrical requirements, or fail to consider integration with the control system. The result? Either the boiler is insufficient, or they unnecessarily pay extra for power they will never fully utilize.

This article will help you avoid these mistakes. I cover everything you need to consider before purchasing – from power through electrical connection, type of heating, control system, to practical scenarios from real customer cases.

What is the electric boiler Buderus Logamax E213 – basic orientation

Buderus Logamax E213 is a compact electric wall-mounted boiler mainly intended for central heating (heating circuit with radiators or floor heating), or for combined connection with preparation of hot domestic water via an external tank. The boiler is not a flow water heater – it does not have an internal hot water tank, which is important to understand from the beginning.

The E213 series is available in five power variants:

4 kW – Buderus Logamax E213-4
6 kW – Buderus Logamax E213-6
8 kW – Buderus Logamax E213-8
10 kW – Buderus Logamax E213-10
14 kW – Buderus Logamax E213-14

All variants have the same physical dimensions of the housing (the difference is only in the internal wiring and number of heating elements), which significantly simplifies any possible replacement with a higher power without construction interventions. The boiler is equipped with a circulation pump, expansion tank, safety valve, and circulation system – it is a closed compact system ready for direct connection to the heating circuit.

Power: the most important parameter when choosing

Boiler power is undoubtedly the most critical decision factor. A boiler that is too weak will simply not heat the house in the cold, while one that is too powerful will cycle on and off in short intervals, which accelerates wear and reduces efficiency.

A basic rule of thumb commonly used in practice: 50–70 W for every m² of floor area in a normally insulated house built before 2010. For low-energy houses (built after 2015, with a specific heat loss value below 30 kWh/m²/year), you can calculate with 30–40 W/m².

Examples from practice:

A house with a floor area of 80 m² (normally insulated brick, new build 2005): power ≈ 80 × 55 W = 4.4 kW → suitable Buderus Logamax E213-6 (6 kW), which covers the heat loss and also allows for hot water load with an external tank.
An older family house of 130 m², partially insulated (facade yes, roof only 10 cm mineral wool): power ≈ 130 × 65 W = 8.5 kW → Buderus Logamax E213-10.
Renovation of an apartment block, 55 m² apartment in a panel building (insulated facade, PVC windows): power ≈ 55 × 40 W = 2.2 kW – here E213-4 is sufficient, while E213-6 provides a comfortable reserve.

A more detailed calculation procedure can be found in the separate article What power of Buderus Logamax electric boiler do I need for my house, where the influence of house orientation, type of windows, and thermal bridges is also discussed.

Important note: if you plan to connect the boiler to heat DHW via an external tank (e.g. 150–200 l), it is necessary to add approximately 1.5–2.5 kW to the calculated heating power. The tank is heated with priority (so-called priority switching), so heating stops during its heating. If the tank has its own heat pump or electric heating element, this is not necessary.

Electrical connection and protection – a critical factor often underestimated

Electric boilers are not light bulbs. Every kilowatt of power requires a corresponding input from the grid. This has a direct impact on the existing electrical installation, protection devices, and even the contract with the electricity distributor.

Boilers up to 6 kW (E213-4 and E213-6) can be operated on a single-phase 230 V network, but at full 6 kW power, this means a current draw of 6000 W ÷ 230 V ≈ 26 A. This requires a circuit breaker of at least 32 A and a supply cable dimensioned for this current (minimum 6 mm² Cu). Many older apartments or family homes have a main circuit breaker of 25 A for the entire household – in such cases, reconstruction of the electrical installation or an agreement with the distributor to increase the protection is necessary.

Boilers of 8 kW and higher (E213-8, E213-10, E213-14) require a three-phase supply of 400 V / 3×N+PE. With a three-phase connection, the load is distributed evenly, which is also advantageous for the distribution system. Requirements for protection:

Model	Power	Supply	Min. circuit breaker	Min. cable cross-section
E213-4	4 kW	230 V / 1-phase	20 A	2.5 mm² Cu
E213-6	6 kW	230 V / 1-phase	32 A	6 mm² Cu
E213-8	8 kW	400 V / 3-phase	3×16 A	3×2.5 mm² Cu
E213-10	10 kW	400 V / 3-phase	3×20 A	3×2.5 mm² Cu
E213-14	14 kW	400 V / 3-phase	3×25 A	3×4 mm² Cu

Always check before ordering what reserved capacity (in kW or A) you have in your contract with the distributor. If you want to increase it, an application must be submitted to the local distribution company (ZSD, VSD or SSE-D depending on the region) – equipping usually takes 4–8 weeks and may require a fee for reinstallation of the main circuit breaker. More on this topic can be found in the article Power supply and electrical requirements of Buderus Logamax boilers – what you need to know.

Heating system type – radiators vs. floor heating

Buderus Logamax E213 operates in a heating circuit with water temperature of 35–80 °C. This makes it compatible with both radiator heating (standard temperature 55–75 °C) and floor heating (optimal 35–45 °C). This is an important advantage compared to some other electric boilers that have a limited temperature range.

For floor heating, the rule applies: lower water temperature = lower heat losses in the circuit, longer warm-up time, more even heat distribution, and higher comfort. The boiler consumes less energy to maintain the temperature in the circuit at 40 °C, which is reflected in the bill. In practice, an equitemperature curve (dependence of water temperature on outdoor temperature) is commonly set for floor heating – for this, you need an outdoor temperature sensor and a control unit (integrated or optional in the E213 series).

In a combined system (some rooms with radiators, others with floor heating), it is advisable to use a mixing unit for the floor heating part, which reduces the temperature of the water from the main circuit to the required 40 °C. The boiler then operates at a higher temperature (e.g., 65 °C for radiators), from which a cooler circuit for the floor is branched off via a mixing valve and a thermostatic valve. This solution is common in renovations, where the original radiator system is supplemented with floor heating in a new extension.

Control and regulation – what the E213 series offers

A modern electric boiler without intelligent regulation is just an expensive heater. Buderus Logamax E213 has an integrated control system with a digital display, where you can set the desired water temperature, daily programs, and other parameters. Basic control functions are available directly on the boiler without the need for an additional unit.

To improve comfort and increase savings, it is advisable to extend the boiler with:

Room thermostat / room control sensor – the boiler adjusts its output according to the actual temperature in the room, not just according to the water temperature. This reduces consumption by up to 15–20 % compared to regulation based only on water temperature.
Outdoor temperature sensor + equitemperature regulation – the boiler already "knows" what the outdoor temperature is and automatically adjusts the water temperature according to the set curve. Particularly suitable for floor heating, where the thermal inertia of the system is high.
Communication with smart home systems – some models of the E213 series are compatible with control systems via Modbus or OpenTherm, allowing integration with KNX, Loxone and similar systems.

A detailed overview of settings and control strategies can be found in the article Control and regulation of the Buderus Logamax E213 boiler performance.

Low-energy and passive houses – a special case

In a low-energy or passive house, heat losses are so low that even the smallest model Buderus Logamax E213-4 may be oversized for heating alone. In practice, I have encountered houses where the specific heat demand is below 20 kWh/m²/year and the house is 120 m² – this means an annual total consumption of only 2,400 kWh. The maximum thermal output at -15 °C outside is in such a house only around 2.5–3 kW.

Despite this, the E213-4 has its justification in a passive house as a backup during extreme cold or as a boiler combined with a heat recovery system. Moreover – if you plan to heat TÚV via an electric storage tank connected to the boiler, the 4 kW power is actually usable for TÚV. More on this topic in the article Buderus Logamax E213 in low-energy and passive houses – is it worth it.

Installation conditions and space requirements

Electric boilers do not have a combustion device, so there are no requirements for air supply, exhaust of combustion gases, or the presence of a chimney. This is a huge advantage in renovations, where there is no chimney or where space conditions exclude gas equipment. The boiler can be installed in a utility room, kitchen, bathroom, technical room – practically anywhere where there is an electrical power supply and access to the heating circuit.

The physical dimensions of the E213 series are the same for all power outputs – the boiler is a compact wall-mounted unit with a height of about 720 mm, width of 390 mm, and depth of 290 mm. The weight ranges from 20 to 25 kg depending on the power. Before installation, it is necessary to:

ensure the wall can support at least 50 kg (including water in the expansion tank and pipes),
leave a minimum of 400 mm of free service space in front of the boiler,
connect the heating circuit (usually a 3/4" or 1" threaded connection),
connect the electrical supply to a fixed socket box with a circuit breaker (not a flexible supply),
connect the discharge from the safety valve to the sewer or a catch basin.

A detailed installation procedure with images can be found in the article Installation of the Buderus Logamax electric boiler – procedure and requirements. I strongly recommend entrusting the installation to a qualified electrician and heating technician, as incorrect electrical connections can lead not only to malfunctions, but also to electric shocks or water leaks.

Operating costs – what affects electricity consumption

Electric boilers have an efficiency approaching 99 %, which is the physical maximum – almost every watt from the socket is converted into heat. Despite this, operating costs can be high, as the price of electricity in Slovakia is still higher compared to gas or wood (although this difference has decreased in recent years).

To reduce costs, we recommend:

Use of night tariff (NT) – in combination with a hot water storage tank (if there is space), where water is heated during NT and drawn from the storage during the day. For a house with a 500 l tank, this can be a realistic saving of 20–35 %.
Photovoltaics – the Buderus Logamax E213 is an ideal consumer for "excess" energy from PV. There are power regulators (power managers) that automatically increase the boiler's power during excess and reduce it during shortage. This connection is very popular.
Proper setting of night setback – do not heat at full temperature unnecessarily during the night or when absent. The E213 series supports time programs directly via the panel.
Thermal insulation of the house – this is a given, but worth mentioning: every boiler, no matter how efficient, consumes as much energy as the house loses.

What to pay attention to when choosing – summary in practice

After years of work with electric boilers, I see that selection errors repeat themselves. Here are the most common ones, so you don't make them:

Choosing by price, not performance: E213-4 is cheaper, but if your house needs 7 kW, you will buy a problem. The increased electricity price in inefficient operation will cost you much more in the end.
Ignoring the electrical connection: Check the capacity of your connection before ordering. If you have 3×25 A and want E213-14, you are on the edge – the circuit breaker may trip with other electricity in the house.
Forgetting about TÚV: The boiler itself does not heat hot water. If you don't have a tank or water heater, you must solve this simultaneously.
Underestimating regulation: A boiler without a thermostat is a waste of energy. At least a simple room thermostat (e.g. digital with a weekly program) is a necessity.
Unrealistic expectations in a panel apartment or flat: If the flat is part of a larger unit with central heating, an electric boiler serves only as a supplement or replacement – it is necessary to verify technical feasibility with the housing company.

Comparison with other electric boilers and alternatives

Buderus Logamax E213 is not the only electric boiler on the market, but it belongs to the proven and reliable mid-range segment. The main advantages over cheaper competitors (e.g. boilers from China under various brands):

Certification for the European market, safety features according to EN standards
Availability of spare parts and service network in Slovakia
Compact cabinet with integrated components (pump, expansion tank, PRV)
Proven long-term reliability of heating elements (corrosion resistance)

Compared to air-to-water heat pumps, an electric boiler has lower acquisition costs (about 3–5 times), simpler installation and higher comfort in extreme cold (heat pumps lose power at -15 °C, electric boilers do not). On the other hand, heat pumps have a COP of 3–4, i.e. for every kW of electricity they produce 3–4 kW of heat, which is more advantageous in the long run. An electric boiler is therefore advantageous where gas/pellet alternatives are not suitable, or as a backup and supplement to a heat pump. A comparison with other electric boilers can be found in the article Buderus Logamax vs. other electric boilers – what distinguishes them.

Service, maintenance and common faults

Electric boilers have significantly fewer moving and wearing parts than gas boilers. Nevertheless, a few things require regular attention:

Pressure in the circuit – check the pressure gauge at least once every 3 months. The standard operating pressure is 1.5–2.0 bar. If the pressure drops, it may indicate a leak in the circuit or a fault in the expansion tank.
Draining air from radiators – air in the circuit slows down the flow and reduces efficiency. Bleed the radiators at the beginning of each season.
Checking for limescale – if you have hard water (hardness above 25 °dH), limescale may deposit on the heating elements. A solution is a water softener at the boiler inlet or regular flushing and cleaning.
Checking the safety valve – once a year, the test valve should be briefly opened and closed to verify its functionality.

A complete overview of service tasks and faults can be found in the articles Maintenance and service of the Buderus Logamax electric boiler and Common faults of the Buderus Logamax electric boiler and their solutions.

Practical scenarios – which model for which house

Based on several real customer cases:

Scenario A – Apartment in an insulated panel building, 68 m²: An apartment unit on the 4th floor, double-sided by other apartments, only two exterior walls. Heat loss ≈ 2.8 kW. No need for DHW (has a flow heater). Solution: E213-4, single-phase power supply, existing 25 A connection is sufficient. Customer satisfied, annual consumption around 1,800 kWh.

Scenario B – Family house 110 m², new build 2019, low-energy standard, heat pump as main source + E213 as backup: The HP covers 85–90% of needs, the boiler activates when the outside temperature drops below -7 °C or in case of HP failure. Selection: E213-8 as backup. Three-phase power supply available. The boiler operates in standby mode, activates 3–5 times during the winter.

Scenario C – Renovation of an older family house 150 m², partial insulation, replacing an old gas boiler with an electric one: The house has a gas connection, but the customer does not want to continue using gas. Estimated heat loss is 10.5 kW. DHW via an external 200 l storage tank. Required power 10.5 + 2 = 12.5 kW. Selection: E213-14 – has a reserve, which is advantageous since the house is not fully insulated and the customer plans to insulate the roof as well.

Scenario D – Cabin, 45 m², occasional use on weekends: The house is not permanently occupied, heating only during visits. Heat loss 2.5 kW. Selection: E213-4, remote control via a GSM thermostat (customer preheats the cabin 6 hours before arrival). The solution works reliably.

Most frequently asked questions (FAQ)

Can I connect the Buderus Logamax E213 to a single-phase connection of 230 V?

Yes, but only for the E213-4 and E213-6 models. These have a power output up to 6 kW and are constructed for single-phase 230 V supply. The E213-8, E213-10 and E213-14 models require a three-phase 400 V (3×N+PE) supply. Attempting to connect an 8 kW or higher model to a single-phase supply would cause overloading of the circuit breaker and damage to the device.

Can the E213 boiler heat DHW for a shower and sink?

Not directly – the E213 boiler itself does not have a DHW tank. It can only heat water if you connect an external storage heater (boiler) with a heat exchanger, which you connect to the boiler's heating circuit. The boiler then heats the water in the tank in priority mode and switches back to heating. This configuration is common and functional, but it is necessary to include DHW consumption in the power calculation.

How much electricity does the Buderus Logamax E213 consume annually?

Consumption depends on the size of the house, its thermal insulation, the climatic zone and the set temperature. Roughly: a well-insulated 100 m² house requires 8,000–12,000 kWh of heat annually, which at 99% boiler efficiency corresponds to the same electricity consumption. A poorly insulated house of the same size can consume up to 18,000–22,000 kWh/year. Therefore, house insulation is much more important than the boiler choice itself.

What if I want to control the boiler remotely via mobile?

The E213 boiler itself does not have a built-in Wi-Fi module, but it can be connected to an external Buderus control unit or a compatible smart thermostat (e.g. Netatmo, Honeywell, Salus with OpenTherm or 0–10V output). Through such a thermostat, you can control the boiler directly from the mobile app. This solution is common and reliable.

Is it possible to replace the E213-6 with the E213-10 without construction changes?

Physically yes – the cabinet dimensions are identical and the hydraulic connections are the same. However, it is necessary to upgrade the electrical connection: the E213-6 runs on a single-phase 230 V, while the E213-10 requires a three-phase 400 V. This requires the intervention of an electrician, new cables and a change of the circuit breaker. The hydraulic part (pipework) does not need to be changed in any case, which significantly reduces the overall cost of the renovation.

Is an electric boiler worth it in times of rising electricity prices?

It depends on the situation. An electric boiler is worth it where there is no gas connection, where the cost of installing gas or a heat pump is disproportionate, or where it serves as a backup to another system. For low-energy houses with PV or with a low tariff, an electric boiler is economically acceptable. For large older houses without insulation, operating costs are high and it is worth considering a heat pump or biomass.

Conclusion – how to make the right decision

Selecting the Buderus Logamax E213 electric boiler is essentially simple if you follow the right approach: start with the heat loss of the house, check the capacity of the electrical connection, decide whether you want DHW heating via the boiler, and then choose the specific power accordingly. There is no point in saving on power and risking underheating, just as there is no point in buying an E213-14 for a 60 m² apartment.

If you are hesitating between two adjacent power levels, always choose the higher one – you still need to have the electrical connection sufficiently dimensioned and a power reserve will ensure that the boiler does not run at 100% capacity all the time (and thus will last longer). If you need help with a specific house or apartment, our technicians will be happy to help with the calculation.

Do you have a question on this topic?

Having trouble deciding or dealing with a specific situation in your home? Write to us – we are happy to help.