Electric convector heater as a main vs. supplementary heating source

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Electric Convector as a Main vs. Supplementary Heat Source: Everything You Need to Know Before Deciding

Electric convectors are among the best-selling types of heating appliances on the Slovak market – and for good reason. They are easy to install, require no water or gas pipework, and can be moved from room to room as needed. Yet customers keep asking the same question over and over: Can I use it as a main heat source, or is it just a supplement? The answer is not simple and depends on a whole range of factors – from the building's heat losses, through electricity availability, to the habits and lifestyle of the people in the household. In this article we will discuss both roles of the convector in detail, with concrete numbers and practical examples, so you can make the right decision.

How an electric convector actually works – the basis for comparison

Before comparing the two roles of the convector, it's important to understand its principle. An electric convector works on the basis of natural convection: cold air enters through the bottom grille, passes around an electric resistance element (or a PTC element), heats up, and exits through the top grille. This creates air circulation that heats the whole room evenly, without any turbulent heat distribution like classic fan heaters produce.

The consequence is simple: a convector cannot create a strong stream of warm air over a long distance, but it can maintain a stable temperature in an enclosed room very efficiently. That's why its performance in practice depends heavily on the quality of the room's thermal insulation and on how much heat "escapes" through windows, doors and walls.

This physical principle has a direct effect on where and how you use a convector. In a well-sealed room with modern insulation, a convector works with very high efficiency – up to 99% of the electrical energy is converted into heat. In an older building with leaky windows and poor insulation, this heat is quickly lost, leading to high electricity consumption and unsatisfactory comfort.

Convector as the main heat source: when it makes sense

Using an electric convector as a primary heating system is nothing unusual. In practice, we've encountered this solution in ten, maybe twenty different types of properties – and in the right context it works great. Let's go through the individual scenarios.

New and well-insulated buildings

Low-energy houses and passive houses with a specific heat demand below 30 kWh/(m²·year) are an ideal environment for electric convectors as the main heating source. Heat losses are so low that maintaining 20–21 °C in the heated room requires only 30–40 W/m², sometimes even less. At this level of load, the convector's operating costs are reasonable despite the higher price of electricity compared to gas.

A typical practical example: a family house from 2018, 120 m² of usable area, wall insulation thickness of 20 cm, triple-glazed windows with a Ug value of 0.6 W/(m²·K). The building's total heat loss at an outdoor temperature of −12 °C reaches approximately 4.5–5 kW. Covering this loss requires 4–5 convectors with a total output of up to 6 kW, which typically operate at 60–70% of output thanks to thermostatic control. Monthly heating costs in January for such a house range from €80–110, which is acceptable for this type of customer.

Apartments in panel and brick buildings

Apartments in panel buildings and brick apartment blocks have one major advantage: neighboring apartments act as a thermal buffer. Heat losses through interior walls are minimal, which reduces overall consumption. Moreover, in apartments the central heating (CH) is often regulated only seasonally, not individually. In such cases, an electric convector is an excellent choice, because the customer doesn't pay for heat they don't need – the thermostat simply switches it off.

A very common scenario: a customer has a 60 m² apartment in a panel building from the 1980s (insulated around 2010), the CH works, but is either oversized or, conversely, insufficient during the transitional season. An electric convector in the living room or bedroom serves as a fine-tuning element and also as a backup in case of CH outages.

Cottages, recreational properties and seasonal heating

This is probably the most natural role for an electric convector as the main source. A cottage that you visit on weekends or only in winter would be needlessly expensive to equip with a gas boiler or heat pump. A few convectors with good control are enough – set a protective (frost-protection) mode of 7–8 °C during the working week, and set a timer or smart control to heat up to a comfortable temperature before arrival.

Practical solution: an 80 m² cottage at low altitude, visited 30–40 weekends a year. Installing 4 convectors with a total output of 5 kW (e.g. a combination of Protherm 1500 in the living room and Protherm 1000 in the bedrooms) covers the entire heating need. The frost-protection mode uses a negligible amount of electricity, since the convector operates only a few hours a day in this mode, or even in cycles.

Transitional spaces and commercial premises

Shops, offices, service centers, veterinary clinics, beauty salons – spaces where people come and go, where heating is only needed during working hours, and where there is no central heating installed. In such spaces, an electric convector works very well as the main heating source, because it needs no servicing, no chimney sweep, and it can easily be expanded or relocated when the space is renovated.

Convector as a supplementary heat source: where it fits best

Equally important – and in practice even more widespread – is the role of the convector as a supplementary, backup, or fine-tuning heating device. This combination occurs in almost every second household and has several logical forms.

Supplement to central heating during the transitional season

The classic case: gas central heating (CH) with a boiler and radiators covers the main heating load in winter. But in March, October and November, when temperatures drop below 10 °C for only a few hours a day, it's not economical to run the entire CH system. An electric convector heats a specific room quickly and only when needed.

This scenario is particularly popular with older boilers that have poorer control – the customer simply leaves the boiler off until November and relies in the meantime on one or two convectors in the rooms where they spend the most time.

Backup in case the primary system fails

Heat pumps, gas boilers, pellet boilers – all these systems can break down. A backup electric convector ensures that if the primary source fails in January, the household won't be left without heating. It's a cheap insurance policy with a dual function – both a fine-tuning element and a backup.

A real-life situation: a customer has an air-to-water heat pump in a family house. During a frosty winter (below −15 °C), the heat pump operates at the limit of its capabilities and needs help. Electric convectors in the coldest rooms (usually corner rooms, rooms with a north-facing wall, attic spaces) fine-tune the temperature and relieve the heat pump during critical hours.

Heating specific zones and rooms

Bathroom, hallway, attic office, garage with a workshop – rooms where the primary heating is weak or absent. In such cases, the electric convector takes on the role of a local supplement, not solving the whole house but addressing a specific problem zone.

For bathrooms, a convector with a higher protection rating (IP44) is a particularly popular choice – not every model meets this, so it's necessary to check the technical data sheet when choosing. The Protherm series of convectors are generally suitable for standard living rooms; for damp spaces, choose models certified for that zone.

Power sizing: numbers you need to know

Without a proper calculation of the required output, any heating decision remains just a guess. The basic rule states that for every m² of heated area you need a certain specific output, which varies according to the quality of the building's thermal insulation:

Passive house (heat loss up to 15 W/m²): 15–25 W/m²
Low-energy house (loss 15–30 W/m²): 25–40 W/m²
Standard new building after 2010 (loss 30–50 W/m²): 40–60 W/m²
Insulated older building (loss 50–80 W/m²): 60–80 W/m²
Uninsulated older building (loss 80–150 W/m²): 80–120 W/m² and more

For a specific room, besides area, you also need to take into account ceiling height (standard 2.5–2.7 m – if higher, calculate by volume), the number and area of windows (each m² of window with U = 1.0 W/(m²·K) loses about 30 W at −12 °C outside and +20 °C inside), north-east orientation (adjust upward by 10–15%), and corner rooms (adjust upward by 10%).

Example: a living room of 24 m², 2.6 m ceiling, one 2 m² window, south-facing, well-insulated new building. Required output: 24 × 50 W = 1200 W, minus 10% for the south orientation = approximately 1080 W. In practice you would choose a convector with an output of 1000–1500 W. For such a space, a great choice would be, for example, the Protherm 1000 with 1000 W output, or, with some reserve, the Protherm 1500 with 1500 W output.

You can find a detailed calculation procedure also in the article What Output Electric Convector Do I Need for My Room in the Knowledge Center.

Economic analysis: when electric heating pays off

This is the sticking point every customer runs into. Electricity in Slovakia is more expensive than natural gas – in 2024 the price of electricity for households ranges from €0.16–0.22/kWh depending on the tariff and distribution area, while natural gas costs approximately €0.07–0.10/kWh (converted to thermal energy). This seemingly speaks clearly against electric heating.

However, reality is more complicated. The comparison must take into account:

Investment costs: A gas boiler with piping and radiators in a new building costs €4,000–8,000. A set of electric convectors for the whole house costs €600–1,500. The savings on investment are "paid back" from operating costs over several years.
D6 tariff / rates for storage and direct electric heating: If you are the main or exclusive source of electric heating, you are entitled to a special tariff with a lower electricity price (in some distribution areas up to 30–40% cheaper than the standard D1 rate). This fundamentally changes the economics.
Servicing and inspection costs: A gas boiler requires an annual inspection (€50–150), a chimney, and burner servicing. An electric convector needs practically nothing – no chimney, no combustion inspection, no fuel servicing.
Lifespan and reliability: Electric resistance heating is technologically very simple. A quality convector lasts 15–25 years without any servicing intervention. A gas boiler has an average lifespan of 12–15 years and requires servicing.

Conclusion of the economic analysis: at the standard D1 tariff, direct electric heating doesn't pay off for large family houses with poor insulation. At the D6 tariff (or newer equivalents) and in well-insulated buildings, the economics balance out dramatically – and once investment costs and maintenance-free operation are taken into account, electric heating can turn out better or comparable.

Control: the heart of efficient electric heating

One of the most common mistakes when installing an electric convector – whether as a main or supplementary source – is underestimating the importance of control. A convector without good control will consume significantly more electricity than necessary. Quality control can reduce consumption by 20–40% compared to simple on/off switching.

Modern electric convectors offer several levels of control:

Mechanical thermostat: a simple bimetallic or capillary sensor, accuracy ±2–3 °C, cheap but less efficient. Suitable for cottages and supplementary use, where investing in more expensive control isn't worthwhile.
Electronic thermostat: accuracy ±0.5 °C, digital display, option to set a weekly program. Significantly more efficient – it maintains the temperature within a narrow range and doesn't heat unnecessarily. The recommended choice for main heating.
Smart/Wi-Fi control: control via an app, remote activation before arriving home, integration with smart home systems. Ideal for cottages and properties with irregular occupancy – it significantly saves energy on days when you're not at home.
Open Window Detection: a feature found in more modern convectors – a sensor detects a rapid temperature drop caused by an open window and automatically switches off heating until the window is closed. A small feature that can nevertheless save tens of euros per season in rooms that are frequently ventilated.

You can read more about these features in the article Convector with Electronic vs. Mechanical Control: Which Is Better in the Knowledge Center.

Mobility vs. fixed installation: what to choose and why

Another practical aspect of the decision: you can install the convector permanently on the wall, or leave it as a free-standing unit on the floor with wheels. Both approaches have their place.

Fixed wall installation is suitable for the main heating source – the convector becomes visually and functionally part of the room, doesn't obstruct movement, the power cable is hidden in the wall, and the overall impression is cleaner. The installation process is described in detail in the article Mounting an Electric Convector on the Wall: Step-by-Step Procedure.

A free-standing solution with wheels is ideal for supplementary use: you can move the convector wherever you need heat, without any construction work. The Set of Wheels for Tesy is an example of supplementary accessory that turns a fixed convector into a mobile solution in a few minutes. You'll appreciate this especially when you want to try out a purchased convector in different rooms first, or when you only heat a certain part of the house and want to move the convector according to the current day. We write more about this topic in the article Wheels for an Electric Convector: When They Are Worth It and What to Know.

Number of convectors vs. one powerful unit: which is the better solution

Customers quite often ask us whether it's better to buy one large convector or several smaller ones. For the main heating system, the answer is almost always: several smaller ones, each in its own room. The reasons are practical:

Each room has its own thermostat and its own control. You can keep the bedroom at 18 °C and the living room at 22 °C – without any compromise.
If a fault occurs in one convector, the rest continue to work normally. One large convector means a single point of failure for the entire area it was meant to cover.
Smaller convectors can be placed under windows, which is the optimal position for counteracting the cold radiation from windows.
More even heat distribution throughout the room – the air isn't heated in just one corner.

On the other hand, one more powerful convector as a supplementary source in a specific room makes perfect sense – for example the Protherm 2000 with 2000 W output as the only convector in a spacious living room, where you only use it to support the existing central heating on freezing days.

Specific models and their suitable applications

To conclude this section, let's look at how the individual output variants of convectors fit into specific scenarios. The Protherm series offers a consistent solution for various needs:

Protherm 500 (500 W) – ideal for small spaces: bathroom, toilet, hallway (up to 8–10 m² in a well-insulated house), or as frost protection in an unheated room. An excellent supplementary convector for spaces where you don't need full thermal comfort, just basic protection.
Protherm 1000 (1000 W) – a universal model, the best-selling type. Suitable for rooms of 12–18 m² in new buildings, or as a supplementary convector for larger spaces. A good price/performance ratio for both supplementary and main heating in smaller rooms.
Protherm 1500 (1500 W) – suitable for living rooms and larger bedrooms of 18–25 m² in energy-efficient buildings. If building an electric heating system as the main system, this power class covers most standard rooms in new buildings.
Protherm 2000 (2000 W) – designed for larger spaces, corner rooms, older buildings with higher heat losses, or spacious living rooms of 25–35 m². As a supplementary source, suitable for large rooms where the primary heating isn't sufficient.

You can find a more detailed comparison of specific brands and models in the article Protherm vs. Tesy Electric Convectors: What's the Difference and Which to Choose.

Combined systems: best of both worlds

In practice, we increasingly encounter hybrid solutions where the primary source is a heat pump or a pellet boiler with a storage tank, and electric convectors serve to fine-tune comfort in specific rooms. This solution has several advantages:

The heat pump covers the base load with a COP (coefficient of performance) of 3–4, which is economically advantageous.
Electric convectors with electronic control fine-tune the temperature in rooms that need a higher or different temperature than other parts of the house – without needing to intervene in the hydraulics.
If the heat pump or boiler fails, the convectors ensure minimum comfort.
During the transitional season, when the heat pump or boiler would operate with low efficiency, it's cheaper to run a convector only where it's needed.

A customer from Trenčín had this system installed this year: an air-to-water heat pump with underfloor heating covers the ground floor of the family house. The attic spaces (2 rooms, 45 m² total) are heated by two electric convectors, Protherm 2000 and Protherm 1500. The attic rooms are used only on weekends, so the convectors are programmed on a weekly schedule. Result: lower investment compared to extending underfloor heating into the attic, independent control of the attic separate from the ground floor, and the customer's satisfaction with all aspects.

Safety and electrical requirements

An electric convector is a relatively undemanding device in terms of safety, but a few basic rules need to be followed, especially if you plan to use it as the main heat source with multiple units at once:

Current load: A 2000 W convector at 230 V draws approximately 8.7 A. A standard 16 A circuit breaker can handle one convector of this output without problems, but with multiple convectors on one circuit (for example 3 × 2000 W = 6 kW = 26 A), the load needs to be split across multiple circuits.
Sizing of the electrical installation: For a main electric heating system, we recommend working with an electrician to size the supply lines and circuit breakers. In practice, for larger installations (over 6 kW total output), a three-phase supply is recommended, with the load evenly distributed across the phases.
Placement: The convector must not be covered by curtains, furniture, or other material. A free space of at least 20–30 cm must be maintained on all sides of the convector.
Grounding: Every convector must be connected to a grounded outlet or directly wired with a protective conductor (PE).

Frequently Asked Questions (FAQ)

Can I use an electric convector as the only heat source in an old, uninsulated house?

Technically yes, but economically it's problematic. In an uninsulated house, heat losses are typically 80–150 W/m², which means a very high output and therefore high electricity consumption. A much better approach is to first insulate (windows, roof, façade) and only then consider electric convectors as the main source. If insulation isn't possible, consider at least the D6 tariff and thorough time-based control – heat only when you're actually home, and maintain a frost-protection temperature the rest of the time.

Is an electric convector safe for continuous operation throughout the winter?

Yes. Electric convectors are designed and certified for continuous operation. They have no moving parts (no fan), which minimizes wear. Quality models have overheating protection (thermal cut-off), which switches off the convector in case of thermostat control failure. It's important to keep the inlet grille clean – dust build-up can lead to overheating. More on this in the article Maintenance and Cleaning of an Electric Convector: How to Extend Its Lifespan.

How many convectors do I need for a whole apartment/house?

Basic rule: one convector for each main heated room. For a small apartment (2 rooms + kitchen), this could be 3–4 convectors. For a 120 m² family house, it's typically 5–7 convectors. Bathrooms, toilets and hallways are handled either with a small convector (500 W) or heated by residual heat from adjacent rooms if the doors are often open. You can find a specific calculation for your layout in the article How to Choose an Electric Convector: Output, Control and Other Criteria.

Is it possible to control multiple convectors centrally, or do I need to set each one separately?

It depends on the model. Convectors with a mechanical thermostat are set individually. Modern models with smart/Wi-Fi control can be integrated into a single app and controlled or programmed as a group. Some systems even allow integration with a smart home (Home Assistant, KNX, etc.). If you're planning electric heating as the main system, it's worth investing in convectors with good digital control – it will pay off in energy savings.

What to do when the convector doesn't heat the room sufficiently?

First: check that the inlet grille is clean (dust can significantly reduce output). Second: verify that the convector's output matches the room's actual heat loss – it often turns out that the calculation was underestimated. Third: check the tightness of windows and doors – in older buildings, leaks are responsible for 20–40% of heat losses. Fourth: if the convector is older and has been in operation for a long time, there may be a problem with the thermostat or the heating element – more in the article Common Faults in Electric Convectors and How to Fix Them.

What does the D6 tariff mean and how do I get it?

The D6 tariff (or its regional equivalents) is a special rate for customers who use electricity for direct heating as the main or dominant source. The price of electricity during the low-tariff period (typically nighttime hours) is significantly lower than the standard rate. The condition is that the convectors form the main heating system, the installation meets the minimum installed output, and the distribution company has carried out an inspection. The contract and conditions vary by distribution area (ZSD, SSD, VSZP). Check with your electricity supplier for details.

Conclusion: main or supplementary? The decision is yours

An electric convector can handle both roles – main and supplementary heating device – provided the right conditions are met. As a main source, it works reliably and economically in well-insulated new buildings, apartments, recreational properties and smaller commercial spaces. As a supplementary source, it's indispensable during the transitional season, as a backup in case the primary system fails, and for individual control of specific rooms.

The key to making the right decision is a realistic calculation of heat losses, a comparison of actual operating costs (taking available tariffs into account), and consideration of investment costs over the long term. Don't be discouraged by a mere rough comparison of electricity and gas prices per kWh – the overall picture is always more complex and, in many cases, speaks in favor of the electric solution.

If you're still not sure which output or model is right for you, check out the other articles in our Knowledge Center, especially How to Choose an Electric Convector: Output, Control and Other Criteria and Frequently Asked Questions About Electric Convectors, where you'll find more practical answers to common situations. You can find the entire range of electric convectors at atria.sk/elektricke-konvektory/.

Do you have a question on this topic?

Can't decide, or dealing with a specific situation in your household? Write to us - we'll be happy to advise.