Difference between SLOKOV SL ELEKTRO and SL ELEKTRO MINI

We are still preparing products.

But you can look at other categories.

Difference between SLOKOV SL ELEKTRO and SL ELEKTRO MINI – complete technical overview

One of the most common questions we receive from customers considering the purchase of an electric boiler from the brand SLOKOV is: “What is the actual difference between the SL ELEKTRO and SL ELEKTRO MINI series, and which one is right for me?" At first glance, it may seem like it's just a smaller version of the same product – but in reality, the differences are deeper and have a direct impact on how the boilers will function in your system, what demands they place on the electrical connection, and for which types of houses they are suitable. This article will thoroughly explain these differences – technically, practically, and without unnecessary phrases.

What is the SLOKOV SL ELEKTRO series – basic overview

The SL ELEKTRO series is the flagship line of electric boilers from the Slovak manufacturer SLOKOV. These are boilers intended primarily for family homes, larger recreational buildings, smaller apartment buildings, and commercial spaces where a higher output, robust regulation, and reliable operation in a long-term continuous mode are required. Boilers in this series are designed to replace a gas or solid fuel boiler without compromising heating comfort.

The output range of the SL ELEKTRO series is significantly wider compared to the MINI variant. On Atria.sk you will find the following specific models:

This range covers most common applications in apartment construction – from a smaller family home with good insulation to older buildings with significantly higher heat loss, or to a building combining heating with the preparation of hot water via a storage tank.

What is the SLOKOV SL ELEKTRO MINI series – basic overview for smaller applications

SL ELEKTRO MINI represents a narrowed, compact variant intended for applications where a high output is not required, and where spatial layout or the electrical connection does not allow the installation of a full-sized larger boiler. The MINI version is typically available in lower output levels and places fewer demands on the building's electrical infrastructure.

From the design philosophy perspective: MINI is not a "worse" version of SL ELEKTRO – it is a product optimized for a different type of use. It makes sense precisely where a larger boiler would be oversized, more expensive to operate, and unnecessarily burden the electrical grid.

Physical dimensions and weight – what it means for installation

One of the most visible differences between the two series is the physical size of the device. The SL ELEKTRO series with higher output is naturally larger – a larger heat exchanger, a greater number of heating elements, a more robust control panel, and a stronger cabinet. The weight of boilers in the SL ELEKTRO series typically ranges from about 30 to 50 kg depending on the output, while the SL ELEKTRO MINI is significantly lighter and more compact, which simplifies handling and installation in confined conditions.

From a practical perspective, this means:

SL ELEKTRO MINI is suitable for a small technical room, a hallway, a large bathroom space, or even a shaft – a place where a larger boiler would simply not fit or where its installation would be complicated.
SL ELEKTRO requires a real technical room or at least enough space on the wall where it will be mounted, and where there is space for operation, inspection, and possible servicing.

Therefore, if a customer says they want a boiler in a small storage niche in the hallway of a panel apartment building, the MINI is almost always the right choice. Conversely, in a family home with a separate boiler room of 4×3 meters, this argument disappears and the choice is determined exclusively by output and features.

Electrical requirements – connection, protection and supply cable

This is one of the most critical differences from the perspective of real installation. Electric boilers are directly dependent on the power of the building’s electrical connection, and this is where the MINI and full-featured SL ELEKTRO models differ significantly.

SL ELEKTRO MINI – single-phase or weaker three-phase connection

Boilers in the MINI range with lower power (typically 2–6 kW) can be connected to a single-phase 230 V network. This is a major advantage when renovating older apartments or buildings where a three-phase connection is not available or where its installation would involve high costs and bureaucratic burden associated with changing the distribution contract.

For higher power levels in the MINI range, a three-phase 400 V network is required, but the current load of the protection is still significantly lower than with boilers from the SL ELEKTRO range.

Practical example: a customer has an old panel apartment with a single-phase connection and a 25 A protection. With such a limitation, you can connect a MINI boiler with a power of up to approximately 5 kW (5 000 W / 230 V = 21.7 A) and still have some reserve for other appliances. With an SL ELEKTRO 10, the average current draw per phase would be approximately 14.4 A (10 000 W / 400 V / 1.73 = approx. 14.4 A), which requires a 16–20 A protection per phase individually and a three-phase connection as a basic condition.

SL ELEKTRO – three-phase network as a basis

All boilers in the SL ELEKTRO range operate exclusively with a three-phase 3×400 V network. This is not just a technical formality – it is a physical necessity dictated by the power. A boiler with a power of 23 kW or 26 kW would require a current of 100 A or more at single-phase supply, which would destroy any household electrical installation.

Dimensioning of the supply cable and protection for individual models:

Model	Power (kW)	Network	Current per phase (A)	Recommended protection
SL ELEKTRO MINI (e.g. 4 kW)	4	1× 230 V	~17.4	25 A / 1F
SL ELEKTRO MINI (e.g. 9 kW)	9	3× 400 V	~13.0	16 A / 3F
SL ELEKTRO 10	10	3× 400 V	~14.4	20 A / 3F
SL ELEKTRO 18	18	3× 400 V	~26.0	32 A / 3F
SL ELEKTRO 26	26	3× 400 V	~37.6	50 A / 3F

These values are approximate – always verify them in the documentation of the specific model and have the connection dimensioning confirmed by a qualified electrician. You will also find more information about the requirements for electrical installation in the article Installation of SLOKOV electric boiler – procedure and requirements in this Knowledge Centre.

Control, control electronics and functions

Both ranges – SL ELEKTRO and SL ELEKTRO MINI – are equipped with an integrated electronic control system with a digital display and the possibility of setting time programs. However, there are certain differences in the depth of control functions and expansion options.

Control in the SL ELEKTRO range

Larger boilers in the SL ELEKTRO range typically have a more sophisticated control system with multiple outputs and inputs. Standard features include:

Setting of daily and weekly time programs for heating
Control of boiler water temperature in the range of typically 30–85 °C
Option to connect an external room thermostat or an OpenTherm controller
Output for controlling a circulation pump
Input for dual-rate measurement (night rate D7 or HDO signal) – which is essential for economical operation, more about this can be found in the article SLOKOV electric boiler and night rate – how to set up heating
Option to control an external hot water storage tank via priority switching

Control in the SL ELEKTRO MINI range

The MINI version has a simpler control system – it is fully functional for standard heating, but the number of inputs and outputs is reduced. Typically, it includes:

Setting of the desired water temperature and basic time program
Input for an external thermostat (dry contact)
Basic HDO (dual-rate) input – depends on the specific model
Limited or no options for integrated control of a hot water storage tank

For a simple system – boiler, circulation pump, radiators, thermostat – the MINI control is fully sufficient. However, if you start considering multi-circuit systems, zoning, floor heating control via a regulated circuit, switching to a hot water storage tank, etc., a larger SL ELEKTRO will provide you with much more flexibility without the need to add external control units.

Hydraulic connection and suitability for different types of systems

Both boilers are connected to the heating system in a standard way – they have a hot water outlet (flow) and a return inlet, and include an integrated circulation pump, expansion vessel and safety valve. Here are a few practical details to keep in mind.

Flow and hydraulics of the MINI version

With the lower output of the boiler in the MINI range, the flow of heating water is proportionally lower and the hydraulic demands on the system are smaller. MINI is ideal for:

A smaller system with one radiator circuit (apartment, small cabin, holiday home)
Connection as an auxiliary/backup heat source in combination with a heat pump or stove insert
Floor heating systems with lower overall output (areas up to approx. 80–120 m²)
Apartment units in inter-apartment heating, where it is used for boosting in cold weather

Hydraulics of SL ELEKTRO – system with a storage tank and multiple circuits

Larger boilers in the SL ELEKTRO range are also designed for more extensive hydraulic systems. A typical customer we see in practice looks like this: a family house of 180 m², floor heating on the ground floor + radiators on the upper floor + a 200-liter TÚV storage tank. Such a system requires a boiler with a minimum output of 15–18 kW, multi-circuit control via a mixing valve and priority switching to the storage tank – which is exactly the domain of the SL ELEKTRO range, not MINI.

Similar hydraulic diagrams and recommended solutions can be found in the article Connecting an electric boiler SLOKOV to an existing system in this Knowledge Center.

For whom is each range really suitable – practical scenarios

Instead of abstract descriptions, let's look at specific types of customers and situations where one or the other range makes more sense.

Scenario 1: Reconstruction of an apartment in a panel building

The customer has a 65 m² apartment, estimated heat loss around 4.5 kW, and a single-phase connection of 230 V, 25 A fuse. In this case, the answer is clear – SL ELEKTRO MINI with an output of 4–6 kW. A larger boiler would not even work here and would not be necessary.

Scenario 2: Low-energy family house 120 m²

A family is building a new house with excellent insulation, calculated heat loss of 6–8 kW, and a three-phase connection is available. Here, the MINI (9 kW) or the smallest SL ELEKTRO (SL ELEKTRO 10) is worth considering. If they plan to add a TÚV storage tank and floor heating with regulation, I recommend SL ELEKTRO 10 – the regulation will allow it without additional external components.

Scenario 3: Older building, house 160 m², gas boiler to be retired

The customer wants to retire the old gas boiler and switch to electric heating. The house is an older brick with an above-average heat loss of around 14–16 kW. Here, MINI is too small, the right choice is SL ELEKTRO 15 or SL ELEKTRO 18 according to the detailed calculation. Also read the article What output of SLOKOV electric boiler do I need for my house?.

Scenario 4: Cabin with occasional heating

A cabin of 80 m², heated only on weekends and holidays, with higher heat loss (older construction), but the customer is not there on the coldest days. SL ELEKTRO MINI is sufficient – quick installation, simple control, lower purchase price. In addition, the cabin may not have a strong three-phase connection.

Scenario 5: Apartment building, common boiler room for 8 apartments

This is a typical application for SL ELEKTRO 23 or SL ELEKTRO 26 – or possibly their combination in a cascade. MINI has no place here, the output is simply insufficient.

Purchase price and operating costs

Naturally, SL ELEKTRO MINI is cheaper to buy. The price difference between the smallest MINI variant and, for example, SL ELEKTRO 10 can be several hundred euros depending on the current price. However, the purchase price of the boiler itself is only part of the total installation costs – with a larger boiler, you must also expect a stronger incoming cable, larger fuse and possibly modification of the distribution board.

On the side of operating costs, there is a direct dependence on output and consumption: if you have a house with a heat loss of 8 kW and you install a MINI 9 kW, the boiler will run at a higher load and for longer. If you installed SL ELEKTRO 10 or 15 – a larger boiler will not turn on for shorter periods due to overdimensioning, because an electric boiler – unlike a gas boiler – does not have a problem with short cycling, provided the thermostat hysteresis is set correctly. The amount of electrical energy will be consumed the same in both cases – as much as the house actually needs.

The differences in operating costs therefore do not stem from the boiler's power itself, but from the tariff (rate) you have and how well the boiler is set up. A significantly cheaper operation is the use of the night rate – and here SL ELEKTRO has an advantage with better regulation and a larger storage tank: it can accumulate heat overnight at a lower electricity price and only reheat during the day.

Common mistakes when choosing – and how to avoid them

After years in practice, we still see the same mistakes that customers make when choosing between MINI and SL ELEKTRO:

Underestimating the heat loss of the house – the customer estimates that a 6 kW MINI is sufficient, but after a detailed calculation, 11 kW comes out. The result is an underheated house and a boiler running at full capacity 24/7 without reserve.
Forgetting about DHW (Domestic Hot Water) – the customer takes a MINI for heating, but wants to connect a hot water tank as well. MINI may not be able to handle it either hardware-wise (missing output) or power-wise (priority hot water heating is energy-intensive).
One-time view on the boiler price – MINI is cheaper, but when the customer later finds out that a higher power is needed, the boiler is replaced and the cost of replacement is also paid. SL ELEKTRO 10 can be a cheaper long-term solution than a higher initial cost when properly dimensioned.
Ignoring the condition of the electrical connection – the customer orders SL ELEKTRO 18, but the connection has only 3×25 A and the distribution board is old. The boiler arrives, the electrician cannot connect it, the result is multiple service charges and delays.

These and other topics are discussed in more detail in the article How to choose an electric boiler SLOKOV – what to pay attention to.

Warranty and service conditions – difference between the models?

From the point of view of warranty and service, the same approach applies to both models – SLOKOV provides a standard legal warranty period with the possibility of an extended warranty upon product registration. The service network is the same for both models, although for larger boilers (SL ELEKTRO with high power) the service call may be more expensive due to the need for an electrician with higher qualifications for boilers over 16 A / 3F.

Practically: service for MINI is simpler and cheaper. However, faults are less common in both models if the installation is done correctly. More about preventive maintenance can be found in the article Maintenance and service of SLOKOV electric boiler.

Cascade connection – advantage of SL ELEKTRO

One of the advanced options that SL ELEKTRO MINI does not actually support is the cascade connection of multiple boilers. In larger buildings – apartment buildings, hotels, production halls – a system is used where two or more boilers in the SL ELEKTRO range work together, with a control unit (master-slave or BMS) distributing the load between them. The advantages are obvious:

Higher overall redundancy – if one boiler fails, the other covers at least part of the power
Smoother performance – at lower load only one boiler runs, at peak load the second one is added
Longer lifespan – each boiler runs fewer hours than it would in a standalone system

For such solutions, a natural choice is, for example, a combination of two SL ELEKTRO 23 or SL ELEKTRO 26 units.

Summary of main differences in a clear table

Parameter	SL ELEKTRO MINI	SL ELEKTRO
Typical power	2 – 9 kW	10 – 26 kW
Power supply	1× 230 V or 3× 400 V	3× 400 V
Physical size	Compact / small	Medium / larger
Control of DHW tank	Limited / no	Yes (integrated)
Multi-circuit regulation	No	Yes
Cascade connection	No	Yes
Suitability for apartment / cottage	Ideal	Overdimensioned
Suitability for family house 150+ m²	Usually insufficient	Ideal
Purchase price	Lower	Higher
Requirements for electrical connection	Lower	Higher

Most frequently asked questions (FAQ)

Can I connect SL ELEKTRO MINI to a single-phase network 230 V?

Yes, but only models MINI with lower power (typically up to 5–6 kW), which are designed for single-phase power supply. Always check the technical specifications of the specific model to see if it supports 230 V / 1F. Higher power models in the MINI range require a three-phase network just like the SL ELEKTRO range. Never connect the boiler to a different voltage than specified by the manufacturer – the risk of damage is high.

Is SL ELEKTRO MINI suitable for a family house with floor heating?

It depends on the size of the house and the heat loss. For a low-energy house up to 80 m² with a calculated heat loss of up to 6–8 kW, MINI may be sufficient. For a larger house with floor heating on the entire area, a DHW tank and multiple circuits, the more reliable and comfortable solution is the SL ELEKTRO range – for example SL ELEKTRO 15 or SL ELEKTRO 18.

Can I later replace SL ELEKTRO MINI with a larger SL ELEKTRO without major construction work?

Yes, the hydraulic connection is compatible – the same diameters, the same connection principle. The replacement will require a new electrician (upgrade of the connection and fuses), but hydraulically it is usually a relatively quick operation. The boiler is mounted on the wall, so it is enough to disconnect the hydraulics, the electricity, remove the MINI and install the SL ELEKTRO. Of course, make sure that the new boiler physically fits where the old one was – the dimensions are larger.

Which boiler range is more suitable for combination with photovoltaics?

Both ranges can be combined with photovoltaics via an external control unit (e.g. energy manager or smart relay). However, SL ELEKTRO generally has a higher potential for efficient integration: its higher power can more quickly absorb excess energy from PV and store it in a hot water tank. With MINI, which has a low power output, the absorption of surpluses is slower, which can reduce the overall rate of self-consumption of PV energy.

Does SL ELEKTRO have better protection against power outages or overvoltages?

Basic protection (fuses, circuit breakers, safety valve, emergency thermostat) is present in both ranges. SL ELEKTRO has more complex electrical protection due to its higher power, but this follows directly from legal requirements for the power class, not from an intentional difference between the ranges. We recommend the installation of overvoltage protection in the distribution board for both boilers – this is a matter of the building's electrical installation, not the boiler itself.

How long does the installation of SL ELEKTRO MINI take compared to SL ELEKTRO?

The installation of MINI is a bit faster – a lighter boiler physically, a simpler connection, less work with insulation. An experienced installer (plumber + electrician) can complete MINI in 4–6 hours from start to operational condition. A larger SL ELEKTRO, for example with 18–26 kW, a storage tank and a multi-circuit distributor, can take a whole workday or more, especially if modifications to the distribution board are needed. A detailed procedure can be found in the article Installation of electric boiler SLOKOV – procedure and requirements.

Conclusion – which range is right for you?

The differences between the SLOKOV SL ELEKTRO and SL ELEKTRO MINI ranges are not only about size. They are about the overall philosophy of use: MINI is an elegant, compact solution for smaller spaces and applications with a limited electrical connection, where high power is not needed. SL ELEKTRO is a full-featured boiler for family homes, larger buildings and systems, where you need not only power, but also advanced regulation, an integrated TÚV control system and the possibility of cascade connection.

The basic rule is: never choose a boiler just based on price or because "a smaller one was enough for the neighbor". Always start from a real calculation of the building's heat loss, the condition of the electrical connection and the planned heating system configuration. If you are unsure, verify your choice with an installer or contact our technical support – such a conversation can save you much more money.

Do you have a question on this topic?

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