Electric boiler vs. gas boiler: when is electric heating worth it?
Electric boiler vs. gas boiler: when does electric heating really pay off?
This question is among the most common ones we encounter when choosing a heating system. Customers ask it in various ways – some directly: "Is an electric boiler cheaper than a gas one?", others ask whether it is worth switching from gas to electricity, or they are looking for a solution for a new build without a gas connection. The answer is not simple or straightforward – it depends on the specific situation, the building condition, the availability of media, investment possibilities, and a long-term view on energy. In this article, we will cover it thoroughly and without embellishment.
Warning in advance: we will not sell you the dream of "the cheapest heating in the world". The goal is for you to be able to objectively assess at the end of the article whether an electric boiler makes sense for your house and your situation.
Basic differences between electric and gas boilers
Before we start comparing costs, it is important to understand how both systems work and in what ways they fundamentally differ.
How does an electric boiler work?
An electric boiler is essentially an electric water heater built into a compact device with control electronics, a circulation pump, an expansion tank, and safety components. Electricity passes through resistance rods (elements) or inductive elements, which directly heat the water in the primary circuit. The efficiency of converting electrical energy into thermal energy is practically 100 % for resistance boilers – all electricity is converted into heat. This is an important technical fact that you should remember.
Devices such as Attack Electric Excellent 15 kW or Attack Electric Easy 8 are typical representatives of this category – compact, easy to install, no fumes, no gas pipe, no chimney.
How does a condensing gas boiler work?
A gas condensing boiler burns natural gas (or propane/butane) in a burner, and the resulting hot exhaust gases transfer heat to the water in the primary circuit via a heat exchanger. Modern condensing boilers can also utilize the latent energy of water vapor from the exhaust gases, achieving efficiency of up to 107–109 % (calculated in relation to the calorific value of the fuel). They are efficient, but they require a gas supply, exhaust of fumes (chimney or coaxial pipe), and regular service maintenance.
Operating costs: the numbers that decide
This is the core of the whole debate. The comparison is not simple because energy prices change quite dramatically – what we experienced in 2021–2023 convinced many people of the instability of energy markets. Despite this, we will make a realistic calculation based on average values.
Electricity price vs. gas price
Approximate prices for a Slovak household consumer (without guarantees, always check the current price list from your supplier):
- Electricity (standard tariff): 0.18–0.24 €/kWh
- Electricity (low tariff, HDO, if approved): 0.12–0.16 €/kWh
- Natural gas: 0.06–0.09 €/kWh (in conversion to calorific value)
From these figures, it follows that you will generally pay 2 to 3 times more for the same amount of heat with electricity compared to gas – if you are heating "hard" with an electric boiler in a standard tariff and comparing it to a condensing gas boiler. This is basic math and there is no sense in hiding it.
Where does an electric boiler become economically interesting? Several factors come into play here:
- Low house consumption – a well-insulated house with low annual heat consumption (e.g., a passive house or a low-energy new build with a need of less than 30–40 kWh/m²/year) has such low total heating costs that the difference between an electric and gas boiler is negligible in absolute terms.
- Absence of a gas connection – when calculating the costs of setting up a gas connection (which can be 1,500–6,000 € or more, depending on the distance and location), an electric boiler is a more investment-friendly start.
- Photovoltaics – a household with a PV system can heat with electricity from its own source, which dramatically changes the economics. If the boiler has access to cheap or "free" surplus from roof panels, the operating economics completely change.
- Combination with HDO – with approval of the night tariff (HDO) and a sufficient heat storage, most of the heating can be done in the cheaper band.
Note: The graph is approximate and is based on a model single-family house of 120 m², consumption of an older building is approx. 100 kWh/m²/year, of a low-energy building approx. 50 kWh/m²/year. The PV scenario assumes 50 % coverage from self-production.
Investment costs and what is actually counted
When a customer comes in and asks which boiler is cheaper, they usually mean only the price of the appliance itself. But this is just a fraction of the total costs. Let's look at the complete picture:
Electric boiler – total investment costs
- The boiler itself: 600–2 500 € (depending on power and model)
- Electrical installation (new circuit breaker, cable, possibly three-phase connection): 300–800 €
- Installation and commissioning: 200–400 €
- Hot water storage tank (if added): 400–900 €
- Total: 1 100–4 600 € (without gas connection, without chimney)
Condensing gas boiler – total investment costs
- The boiler itself: 800–2 500 €
- Gas connection (if not existing): 0–6 000 € (large variability!)
- Chimney or coaxial flue: 200–1 500 €
- Installation, inspection, commissioning: 400–700 €
- Annual service inspection: 80–150 € per year
- Total (without connection): 1 400–4 700 €; with connection: up to 10 000 €+
From this comparison it is clear that an electric boiler can be significantly cheaper in terms of investment, especially in areas without a gas network or when relocating to places where the connection would be expensive.
When an electric boiler really pays off – concrete scenarios from practice
This is the section where practice speaks. The following situations are real – we encounter them repeatedly.
Scenario 1: Cottage or recreational building without gas
A mountain cottage, a weekend house in the countryside, a garden house – typical buildings without a gas connection and with low annual heat consumption. The building is heated a few times a month, not continuously. Here, an electric boiler makes 100% sense. Low investment costs, simple installation, no need for gas service. For example, Attack Electric Easy 8 is an ideal solution for smaller buildings – compact, affordable, and without unnecessary complexity.
Scenario 2: New low-energy construction without a gas network
Developers and self-investors are building new buildings in places where the gas network is not yet developed. The costs of gasification would be disproportionate. The house is designed with low heat demand (under 50 kWh/m²/year), with low-temperature floor heating. An electric boiler works efficiently here, operating costs are acceptable and the whole system is simple. When combined with photovoltaics, the situation improves even more significantly.
Scenario 3: Backup or supplementary heating
Many houses have primary heating on solid fuel, heat pump or another source – but want to have a backup in case of failure, gas supply interruption or simply for transition. An electric boiler connected as a secondary source is an elegant solution. It does not have to cover the entire thermal load, it is enough to handle the transitional period.
Scenario 4: Transitional phase during renovation
The customer is renovating a house and plans to install a heat pump after the insulation is completed. In the meantime, heating is needed – an electric boiler is an ideal temporary solution with minimal investment. Later it can remain as a backup or be removed.
Scenario 5: House with photovoltaics and battery storage
This is a growing segment. The customer has an 8–12 kWp PV system, a battery, and wants to maximize self-consumption. An electric boiler with regulation can absorb PV surplus energy and convert it into heat – either directly into heating water or into a hot water storage tank. Result? The operating cost of electricity for heating really moves around 0.02–0.05 €/kWh (self-production minus marginal costs). Here, the electric boiler economically outperforms everything else.
Ecological aspect: carbon footprint and the future of energy
An electric boiler itself has no emissions at the point of operation. This is important for people with allergies, for buildings in urban zones with emission restrictions, or simply for those who care about air quality around the house. On the other hand, electricity in Slovakia is not 100% renewable – it still contains a share from fossil fuels and nuclear. But if you combine an electric boiler with your own photovoltaics, your operational carbon footprint approaches zero.
The long-term trend is clear: energy is being electrified. Natural gas will gradually become more expensive due to emission permit prices, pressure for decarbonization and geopolitics. Electricity, on the other hand, is gaining an increasingly larger share from renewable sources and its relative price compared to gas could change significantly in the 10–20 year horizon. Investing in electric heating today can be a sensible long-term bet.
Comfort, safety and maintenance requirements
Here, the electric boiler is clearly the winner on all fronts. No chimney, no combustion, no risk of gas or CO leaks. Installation does not require a certified gas technician, inspections are simpler, and daily maintenance is practically non-existent. The boiler is turned on, the controller handles the temperature, and the customer doesn't worry.
Gas boilers require annual service inspections (a legal requirement), cleaning of the condensate system, and checking of hot components. These are not dramatic burdens, but they are real costs and concerns that simply disappear with an electric boiler.
Control and energy-saving options with electric boilers
Modern electric boilers are equipped with sophisticated control electronics. Models such as Attack Electric Excellent 8, 7.5 kW or Attack Electric Excellent 24, 22 kW offer smooth power regulation – this means the boiler does not constantly consume full power, but modulates according to current demand. In combination with a room thermostat, an equithermal control system, or a smart home system, the operating consumption achieves significantly lower values than with a simple "on/off" system.
An important option is the HDO tariff (mass remote control), which is offered by distributors for heating appliances. During night hours (typically 8 hours per day with a dual tariff meter), the price of electricity is significantly lower. If the boiler has sufficient thermal storage in the tank, it can perform most of the heating precisely in this low-cost period.
More on this topic can be found in the article Control and settings of the Attack Electric boiler: how to save on electricity? in the Knowledge Center.
Preparation of hot domestic water (HDW)
An electric boiler itself heats water in a closed primary heating circuit. To prepare hot potable water, an external tank is required. For this purpose, for example, the HDW module (preparation of HDW in an external tank) can be used, which allows connecting a hot water tank directly into the boiler system. The boiler can then alternately heat the heating water and the HDW tank, with control taking place automatically according to set priorities.
A detailed description of the function, tank sizing, and connection diagrams can be found in the article HDW module for an electric boiler: how does the preparation of hot water in an external tank work?
Comparison of electric and gas boilers: summary table
| Criterion | Electric boiler | Gas boiler |
|---|---|---|
| Investment costs | Lower (no connection, chimney) | Higher (connection, chimney, inspections) |
| Operating costs | Higher (without PV), low (with PV) | Lower (standard operation) |
| Service and maintenance | Minimal, no mandatory inspection | Annual inspection, cleaning |
| Safety | Very high (no emissions) | High (with proper installation) |
| Ecology (operation) | Zero local emissions | Low emissions (CO₂, NOx) |
| Compactness | Very compact, light | Compact, requires flue |
| Combination with PV | Ideal, direct integration | No direct connection |
| Availability of medium | Electricity almost everywhere | Gas only where there is a grid |
| Lifespan | 15–25 years (fewer moving parts) | 12–20 years |
Electric boiler as part of a larger home energy system
More and more customers are not thinking of a boiler as an isolated appliance, but as part of a comprehensive energy concept. In this context, an electric boiler proves to be an exceptionally flexible component – it can absorb excess electricity from PV, work in synergy with a heat pump (as a backup or supplementary source), integrate into smart home systems, and respond to price signals from the grid.
In practice, it might look like this: the heat pump efficiently covers the base of the heating season, while the electric boiler takes over on days of extreme cold, when the heat pump would operate with a low COP. The result is a combination of low operating costs and reliability.
For the correct selection of model and capacity, we recommend the article What electric boiler capacity do I need for my house? and Attack Electric Excellent vs. Easy: what are the differences and which one to choose? – both can be found in the Knowledge Centre.
What to pay attention to when switching from gas to electricity
If you are considering replacing a gas boiler with an electric one, there are a few things you should check before purchasing:
- Capacity of the electrical connection – for a boiler with a power of 12–24 kW, you need a three-phase connection of 3×25 A or 3×32 A. This must be verified with the electricity distributor, and you may need to request an increase in reserved capacity.
- Condition of the heating system – older radiators designed for a temperature drop of 75/65 °C (high-temp system) may have slightly lower performance when switching to an electric boiler. An electric boiler is capable of delivering high temperatures as well; it is not a technical obstacle, but it is good to be aware of.
- Water volume in the system – smaller system volumes (radiators without thermal storage) require precise regulation to avoid unnecessary boiler cycling. Some models of Attack Electric Excellent address this situation with continuous power regulation.
- Tariff and metering – request the distributor to assess eligibility for the heating tariff HDO, which can significantly reduce operating costs.
Detailed technical requirements and the installation procedure can be found in the article Installation of the Attack Electric boiler: procedure, requirements, and connection.
Frequently asked questions (FAQ)
Is an electric boiler suitable for an older, poorly insulated house?
In principle, yes – it works technically in any house with a heating system. However, the operating costs may be an issue. An older house with an annual heat consumption of 100–150 kWh/m²/year will have significantly higher electricity bills with an electric boiler compared to a gas boiler. In such a case, we recommend first considering insulation and then choosing the heating medium. An electric boiler is only cost-effective in such a situation as a temporary solution or backup.
Do I need a three-phase connection for an electric boiler?
For capacities up to 3.5 kW, a single-phase connection is sufficient. For typical family homes with a demand of 6–24 kW, a three-phase connection (400 V, 3×16 A to 3×32 A depending on the power) is necessary. Always verify the actual reserved capacity in your connection before installation – changes can take several weeks and may be charged.
Can I combine an electric boiler with underfloor heating?
Yes, an electric boiler is actually more advantageous for underfloor heating than a conventional high-temperature boiler – underfloor heating operates with a heat transfer water temperature of 30–45 °C, which is an ideal operating point for an electric boiler. Regulation is simple and consumption is lower. If you are replacing an old radiator system with underfloor heating, switching to an electric boiler makes good sense.
How much does the annual operation of an electric boiler cost in a typical house?
For a well-insulated family house with a floor area of 120 m² and a heat demand of 50 kWh/m²/year (total 6,000 kWh/year) at a price of 0.20 €/kWh, the annual heating cost is approximately 1,200 €. With the HDO tariff and 60% heating during the night tariff (0.13 €/kWh), it drops to about 820 €. With 50% coverage from PV, it further decreases to about 500–600 €. For an older, poorly insulated building, the figures are significantly higher.
What is the lifespan of an electric boiler compared to a gas boiler?
An electric boiler generally has a longer lifespan because it does not contain burners, heat exchangers exposed to flue gases, or condensation systems. The main wear parts are the heating elements, the circulation pump, and the control electronics. With regular maintenance (flushing, checking the anode if there is a tank, checking the pressure), the lifespan ranges from 15 to 25 years. More on maintenance can be found in the article Maintenance and service of the Attack Electric boiler: what and when to check?
Is it possible to operate an electric boiler without internet or a smart home system?
Certainly. An electric boiler operates fully autonomously without any internet connection. Basic regulation using a built-in thermostat or an external room thermostat is standard and does not require any smart technology. The option of remote control and integration is an additional functionality, not a condition for operation.
Conclusion: when to choose an electric boiler?
An electric boiler is not a solution for everyone, and it would be misleading to claim otherwise. It is, however, an excellent solution for specific situations – and in those situations, it truly excels. If your house does not have a gas connection, if it is well-insulated, if you plan to install photovoltaics, if you are looking for a backup to an existing system, if you are dealing with a cabin or recreational property, or if you simply want the simplest, safest, and most straightforward heating system – an electric boiler is the right choice.
The key is not to focus only on the price of the boiler, but on the overall energy concept of the house. In this regard, electric heating – especially in combination with good insulation and renewable energy sources – has a bright future ahead. You can find the range of devices in the category Attack Electric, where the full range of models is available from the compact Attack Electric Easy 8 for smaller buildings up to the powerful Attack Electric Excellent 24, 22 kW for larger family homes.
Do you have a question about this topic?
Not sure what to choose or dealing with a specific situation in your household? Write to us – we are happy to help.