Converting from Gas Heating to an ELÍZ Electric Boiler: What You Need to Know

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Converting from Gas Heating to an ELÍZ Electric Boiler: What You Need to Know

Every year, more and more households in Slovakia decide to abandon gas heating. The reasons are varied – rising gas prices, the administrative burden associated with regular inspections and servicing of gas appliances, moving away from fossil fuels for environmental reasons, or simply the desire to simplify life and reduce dependence on a single energy supplier. An electric boiler represents a technically elegant solution: it fits into an existing heating system without radical construction work, requires no chimney or fuel storage, and operation is almost maintenance-free.

At the same time, the conversion is not a weekend job with a few screws. Anyone used to a gas boiler must prepare for a series of practical decisions – from the electrical connection to selecting the right output and setting up the controls. This article will guide you through the entire process step by step, with specific values, practical examples, and tips on how to avoid the most common mistakes.

Why People Switch from Gas to Electricity: Real-World Reasons

Looking at the dozens of jobs handled every season, several recurring scenarios emerge. The first is purely economic: gas prices changed dramatically between 2021 and 2023, and although they have partially stabilized, many customers have lost confidence in their predictability. Fixed electricity tariffs are psychologically more acceptable, and if a household has a photovoltaic roof, electricity from its own production makes an electric boiler an even more attractive choice.

The second scenario: the old gas boiler has reached the end of its life. The customer faces a decision – invest in a new gas boiler (€10,000–15,000 including installation of a condensing boiler with controls), or consider an alternative. An ELÍZ electric boiler of comparable output is significantly cheaper to purchase, and installation can be handled by an electrician with minimal cooperation from a heating technician.

The third scenario concerns properties where gas simply isn't available: cottages, holiday homes, small workshops, or properties on the outskirts of a village without a gas connection. In such cases, an electric boiler is the natural and only sensible choice in the category of water-based central heating.

The Basic Principle of an Electric Boiler vs. a Gas Boiler: Technical Comparison

A gas boiler burns natural gas in a burner, transfers the heat via a heat exchanger to the heating water, and the exhaust gases are vented through a chimney or a plastic flue system. This entire chain involves mechanical and chemical processes – which is why annual service inspections, burner cleaning, seal checks, and mandatory gas pipeline inspections are required.

The ELÍZ electric boiler works in a radically simpler way: electricity passes through resistive heating elements (in some types, tubular electric heaters) that heat the water directly. No combustion, no exhaust gases, no chimney. Efficiency approaches 99%, since almost all the electrical energy is converted into heat. The only "loss" is minimal heat radiation into the surroundings through the unit's casing.

Control is usually electronic and allows for smoother output regulation. An electric boiler can operate at partial output – for example, 2 kW out of a total of 8 kW – which is energy-efficient during transitional periods (spring, autumn).

What Stays the Same and What Changes When Converting the Heating System

Good news for anyone considering a conversion: the heating system – radiators, pipework, expansion tank, distributor, circulation pump – mostly remains completely unchanged when converting from gas to an electric boiler. The electric boiler connects to the same fittings; instead of the gas inlet, an electrical cable is connected. This is one of the strongest arguments in favor of this solution.

What changes and what needs to be addressed:

Electrical connection and fuse protection: This is the most common and most important item to address first. The gas boiler only needed a standard 230 V outlet. An electric boiler with an output of 6–12 kW requires a single-phase or three-phase connection with appropriate fuse protection.
Termination of the gas connection: After the conversion, you need to contact the gas company and request disconnection of the gas supply. This is an administrative, not a technical, hurdle, but it must be taken into account.
Bleeding the system: When replacing the boiler, the system is partially opened, which can introduce air. Bleeding the radiators is necessary after any such operation.
Control settings: An electric boiler has different control settings than a gas boiler. You need to set the temperature curves, time programs, and possibly connect it to a thermostat.
Safety valve and expansion tank: These components are usually retained, but their condition and functionality should be checked.
Domestic hot water tank: A gas boiler usually also heated domestic hot water. The ELÍZ electric boiler is primarily focused on heating; hot water needs to be handled with an electric water heater or another system.

Electrical Connection: The Most Critical Technical Point of the Entire Conversion

This is where most customers get their first "wake-up call". The gas boiler only needed an electrical outlet for the control electronics and the circulation pump – i.e., a standard 230 V circuit with a 10–16 A circuit breaker. An electric boiler with an output of 8 kW requires a completely different approach.

Approximate requirements based on boiler output:

Boiler Output	Voltage	Recommended Breaker	Cable Cross-Section
Up to 3.5 kW	1×230 V	B16 A	3×2.5 mm²
4–6 kW	3×400 V	B10–B16 A	4×2.5 mm²
7–12 kW	3×400 V	B16–B20 A	4×4–4×6 mm²
12–24 kW	3×400 V	B20–B32 A	4×6–4×10 mm²

Important: electrical work on the boiler's power circuit must be carried out by a qualified electrician, and the installation must be documented with an inspection report. Without this, your home insurance will not be valid in the event of damage. Before purchasing the boiler, get a preliminary estimate from an electrical installation company – the cost of expanding the home's distribution board and running a new cable can range from €200 to €800 depending on the distance and the condition of the existing wiring.

Another important element is ripple control (mass remote control) – a system used by the distribution company to switch to the low-energy tariff. If you want to operate the boiler partially on the cheaper low tariff (LT), you need to have a rate such as D45N or similar, and the boiler must be connected via a ripple control switch. Arrange this directly with your electricity supplier before installation.

Choosing the Right Output for an ELÍZ Boiler During Conversion

A nice feature of ELÍZ electric boilers is that their sizing follows the same thermal calculations as gas boilers. If you had an 18 kW gas boiler and the house was well heated, you don't necessarily need an electric boiler of the same output. Why? Because most gas boilers were oversized – installers historically preferred to add an extra 2–3 kW "just in case," which wasn't much of an issue with gas, but with electricity it can needlessly increase the cost of the connection.

A rough rule of thumb: a well-insulated family house needs approximately 40–60 W/m² of floor area, an older, uninsulated building 80–120 W/m².

New build, 120 m², low-energy standard → 5–7 kW
House from the 1970s, 150 m², partially insulated → 9–12 kW
Older villa, 200 m², uninsulated → 16–20 kW
Holiday cottage, 60 m², average insulation → 4–6 kW

For a more detailed calculation of the required output, see the article What Output ELÍZ Electric Boiler Do I Need for My House, which contains detailed tables and calculation methodology.

A specific real-world example: a family house in Trnava, brick + 10 cm polystyrene insulation, 140 m², two floors. The old gas boiler had an output of 24 kW. After a proper thermal calculation, the actual need came to 9.5 kW. The customer installed an ELÍZ EQH 802 with an 8 kW output, and the system worked without any problems even at an outdoor temperature of −15 °C. The savings on the connection (not having to run a cable rated for 32 A) amounted to several hundred euros.

The ELÍZ EQH 802 Model: What It Offers When Converting from a Gas System

The ELÍZ EQH 802 is a boiler with a maximum output of 8 kW, which is well suited for compact family homes and holiday properties during a conversion from gas. It operates on a three-phase 3×400 V power supply, which is the standard distribution grid for most Slovak households. The output is adjustable in stages – the boiler doesn't always have to run at full power, which is a key feature for efficient control during transitional periods.

Why is this particular model suitable for conversions? Its dimensions fit into the space where the gas boiler used to hang – quite literally. The hydraulic connections are standard (usually G ¾" or G 1"), the electrical connection is prepared in a box near the boiler, and the entire installation takes just one working day with a skilled heating technician and electrician.

The boiler has built-in frost protection, adjustable outlet temperature, and the option to connect a room thermostat. These features were standard with old gas boilers, but with an electric alternative, they need to be deliberately checked when choosing a model – and the ELÍZ EQH 802 covers all of them.

Step-by-Step Conversion Process

The conversion process isn't complicated, but it requires coordination between several tradespeople and institutions. The most common mistake? Customers buy the boiler and only afterward find out that the electrical connection is insufficient. The correct order is the opposite: first find out the state of the connection, then select the boiler output, then order the equipment.

The gas disconnection step requires a certified gas technician. They will shut off the gas pipeline, draw up a protocol, and notify the distributor. If the chimney was built of brick, you can leave it in place – it won't be in the way, and you may be able to use it in the future, for example when installing a fireplace insert.

Domestic Hot Water Solutions After Removing the Gas Boiler

In most households, the gas boiler was a combi boiler (with a tank or instantaneous type) – it heated both the heating water and domestic hot water at the same time. The ELÍZ electric boiler is primarily a heating boiler. Domestic hot water therefore needs to be handled differently.

There are three options:

Electric storage water heater: The simplest and cheapest solution. An 80–150 liter tank on 230 V, wall-mounted, operated during the off-peak tariff. Equipment cost €150–350, installation an additional €100–200.
Air-to-water heat pump for domestic hot water only (so-called aerothermal water heater): More efficient, but more expensive to purchase (€600–1,500). A COP of around 3.0 means that for every 1 kWh of electrical energy, you get 3 kWh of heat. Suitable for households with higher domestic hot water consumption or those looking for long-term savings.
Solar domestic hot water heater: A combination with a solar collector and a storage tank. Excellent for houses with a south-facing roof, but requires an investment of €2,000–5,000 including installation, and is weather-dependent.

For most households converting from gas to an electric boiler, a water heater is the quickest and most economical solution. If you're interested in long-term efficiency and are willing to invest, consider an aerothermal water heater.

Operating Costs: Gas vs. Electricity – A Real-World Calculation

Cost comparison depends primarily on the tariff under which you're billed for electricity. If you pay the standard high tariff without ripple control, an electric boiler will cost you more per year than gas. This is a key point to understand before making a decision.

The situation changes with ripple control – mass remote control and the low-tariff LT. The distributor allows the large-consumption appliance (the boiler) to operate partly during night hours at a significantly lower electricity price. Combined with a sufficiently large heat storage tank (or buffer tank), you can deliver most of the energy to the system precisely during the cheap hours.

The best-case scenario occurs when combining photovoltaics with an electric boiler. Surplus self-generated energy that you can't feed back into the grid gets "pumped" into the heating system. For more on this topic, see the article ELÍZ Electric Boiler and Photovoltaics: Is the Combination Worth It?.

Summary from practice: a customer with the D45N rate (ripple control), 150 m², moderately insulated house – when switching from gas to an ELÍZ electric boiler, recorded an annual savings of €300–600, including the savings on gas equipment servicing and inspections (which used to cost €150–250 per year).

Compatibility with Old Heating Systems: What to Check

Converting to an electric boiler opens up an opportunity for a general inspection of the heating system. Over years of operation, sediment, sludge, and corrosion products accumulate in the system – especially in older steel pipes. These contaminants shorten the lifespan of the electric boiler's heating elements, as sediment sticks to them and reduces heat transfer.

Before installing an electric boiler, it is recommended to:

Flush the system: Mechanical or chemical cleaning of the pipes and radiators. Cost €100–300 depending on the size of the system. Always worth it if the system is more than 10 years old.
Install a magnetic filter (sludge trap): This device captures ferromagnetic particles from the water before it enters the boiler. For electric heaters, this is an investment that pays for itself many times over by extending the lifespan of the heating elements.
Check the expansion tank: A membrane-type expansion tank loses membrane pressure over the years. Inflate it to a value corresponding to the static pressure of the system (usually 0.5–1.0 bar at ground level).
Check the circulation pump: Old, low-efficiency pumps needlessly consume electrical energy. Modern EC pumps (e.g., Grundfos Alpha or Wilo Yonos) consume 5–10 W compared to 40–80 W for an old pump and pay for themselves within 3 years.
Check the system for leaks: The pressure in a cold system should be stable at 1.2–1.5 bar. If it's dropping, the system is leaking and air is getting in – which is a problem for electric heaters.

Control and Regulation: What an Electric Boiler Offers Compared to Gas

Modern gas condensing boilers have sophisticated control systems with weather-compensated control, OpenTherm communication, and smartphone apps. ELÍZ electric boilers offer a direct-control solution – outlet temperature, thermostats, and time programs.

In practice, this means: you set the desired outlet temperature (e.g., 55 °C for classic radiators or 35–40 °C for underfloor heating), connect a room thermostat, and the boiler cycles on and off as needed. For houses with well-designed controls, this is a completely sufficient solution.

If you have underfloor heating with low outlet temperatures (30–40 °C), an electric boiler is even more advantageous than a condensing gas boiler, because a condensing boiler achieves maximum efficiency at low outlet temperatures, whereas an electric boiler is just as efficient at 35 °C as at 70 °C – the efficiency of converting electricity to heat is 99% regardless of temperature.

Details on setting up the controls can be found in the article Setting Up and Programming the Controls of an ELÍZ Electric Boiler.

Administrative Requirements for Conversion

Many customers underestimate the administrative side of the conversion. Summary of requirements:

Termination of gas supply: Contacting the gas distributor (e.g., SPP Distribúcia), filling out an application to terminate the supply point, physical disconnection by a gas technician. Deadlines are usually 14–30 days.
Change of electricity tariff: Submitting a request to the electricity supplier for a product/tariff change – e.g., switching to D45N or D56N, which allow operation of an electric heating appliance at a lower rate.
Registering the ripple-control appliance: If you want to use ripple control, you must register the new appliance in writing with the distributor (not the supplier). The distributor will register the appliance and set up the ripple-control relay switching.
Electrical inspection report: The installation of the boiler's power circuit must be documented with an inspection report from a qualified inspection technician.
Building permit: If the building is subject to construction documentation and the energy source is changing (e.g., for the energy performance certificate documentation), an update is required. In practice, for family houses, this is handled through a notification of building modification, not a full building permit.

Most Common Mistakes When Converting from Gas to an Electric Boiler

Experience shows several mistakes that customers make repeatedly:

Buying a boiler without checking the connection: A customer orders a 12 kW boiler, only to find out the house has a single-phase 25 A connection and expansion would cost another €1,500. Always consult an electrician first, then place the order.
Ignoring domestic hot water: A customer disconnects the gas boiler and forgets that it also heated hot water. Result: a cold shower. Domestic hot water needs to be addressed in parallel with the heating conversion.
Not cleaning the system before installation: Sludge and sediment from 20 years of operation will destroy the electric boiler's heating element within 2–3 seasons.
Unnecessary oversizing: "Just in case," customers buy a boiler with 50% more output than they need – but they pay unnecessarily for the electrical connection needed for 16 kW.
Operating without the night tariff: The boiler runs all day on the high tariff. Without ripple control and the night tariff, electric heating quickly becomes very expensive.
Not replacing the circulation pump: An old pump consuming 60 W runs 3,000+ hours a year – that's 180 kWh, which at €0.20/kWh comes to an extra €36 per year just for the pump. An EC pump consumes 10 times less.

Electric Boilers and Safety: What Improves with Conversion

Gas heating carries risks that disappear with electricity: natural gas leaks, risk of carbon monoxide (CO) poisoning, and improper exhaust venting. These risks are low with proper installation and maintenance, but not zero. Every year, dozens of CO poisoning cases from malfunctioning gas appliances are recorded in Slovakia.

An electric boiler eliminates these risks. No combustion – no CO, no exhaust gases, no need for a chimney. The safety features of an electric boiler (safety thermostat, safety valve, overheating protection) are simple and reliable. For more on how to take care of an electric boiler, see the article Maintenance and Servicing of an ELÍZ Electric Boiler: How to Extend Its Lifespan.

FAQ – Frequently Asked Questions About Converting from Gas to an ELÍZ Electric Boiler

Do I need to replace the radiators and pipework, or is it enough to just replace the boiler?

In the vast majority of cases, it is sufficient to replace just the boiler itself. The existing radiators, pipework, circulation pump, and other heating system components remain unchanged. The electric boiler connects to the same hydraulic fittings (possibly with reducers). However, we recommend cleaning the system and checking the expansion tank, pump, and safety valve – not because of boiler requirements, but because of the overall condition of the system after years of operation.

How long does the entire conversion take, from decision to start-up?

Realistically, plan for 2–6 weeks. One week for consultations and ordering the equipment, a week to prepare the electrical connection (electrician), another for disconnecting the gas (the distributor has a 14–30 day deadline), and the boiler installation itself takes 1–2 days. If everything is organizationally in place, the technical conversion can go faster – but the administrative process with the gas company takes time.

Is the conversion economically worthwhile if I have an old but functional gas boiler?

It depends on several factors: gas vs. electricity prices under your tariff, the condition of the gas boiler (how much longer it will last without investment), the cost of the electrical connection, and the availability of the ripple-control night tariff. As a rough guide: if your annual inspections, servicing, and gas cost more than €1,500, and you have access to the ripple-control tariff, the payback period for investing in an ELÍZ electric boiler (including the connection) is 3–6 years. If you're planning to add photovoltaics, the payback period shortens to 2–4 years.

Can I connect the ELÍZ electric boiler to an existing domestic hot water tank that was part of the gas system?

It depends on the type of tank. If the tank was heated via a heat exchanger coil (indirect domestic hot water preparation from the boiler circuit), you can connect it to the electric boiler and it will heat the water the same way. However, the ELÍZ boiler is not designed for simultaneous intensive domestic hot water heating and space heating – so it's better to have a separate electric water heater for hot water. If the tank was a direct-heating type (with its own electric element), it works completely independently regardless of the boiler change.

What impact does the conversion have on property value and the energy performance certificate?

The building's energy performance certificate changes when the energy source changes. An electric boiler typically shifts the building into a worse energy class (in terms of primary energy, where electricity has a higher conversion factor than gas). However, if you add photovoltaics at the same time, the situation can be reversed. In terms of the property's resale value, the market currently values mainly low dependence on a single fuel, simplicity of operation, and low service costs. Updating the energy performance certificate is mandatory when changing the heat source before selling a property.

Can the ELÍZ electric boiler handle extreme frosts below −15 °C?

Yes, if properly sized. The ELÍZ electric boiler operates at 100% output regardless of outdoor temperature – unlike a heat pump, whose output drops during frost. The key is to have sufficient installed output for the design outdoor temperature of your location (in Slovakia, −12 to −18 °C depending on the region). If you didn't choose too low an output during the thermal calculation, and the house has at least average insulation, an electric boiler will handle even severe winters without problems. For more on calculations, see the article What Output ELÍZ Electric Boiler Do I Need for My House.

Conclusion: Converting from Gas to an ELÍZ Electric Boiler Is Feasible, But Requires Preparation

Converting from gas heating to an ELÍZ electric boiler is a technically simple operation – provided you've thought through the electrical connection, boiler output, and hot water solution in advance. The heating system remains unchanged, installation takes one day, and operation is subsequently genuinely maintenance-free compared to gas.

Economically, the conversion is worthwhile especially in combination with a ripple-control tariff and photovoltaics. Simply switching to electricity under a standard tariff without optimizing consumption can end up being more expensive – which is why setting up the right product with your electricity supplier is a step that absolutely should not be underestimated.

A specific unit, such as the ELÍZ EQH 802, offers an output of 8 kW, simple controls, and compact dimensions suitable for most family homes in the 80–130 m² range (depending on insulation). For a more detailed model selection based on parameters, check out the entire category of ELÍZ electric boilers, where you'll find the complete range including higher outputs.

If you have questions about installation, check out the article Installing an ELÍZ Electric Boiler: Procedure and Installation Requirements, and for potential future operating issues, the article Common Faults in ELÍZ Electric Boilers and Their Solutions. All of these materials can be found in the same Knowledge Center.

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