Electric boiler Daline PTE and electricity tariff for electric heating – how to save
Electric boiler Daline PTE and electric heating tariff – how to actually save money
Electric heating has a reputation among people as an expensive solution. This reputation is not entirely unfair – if someone ran direct electric heating without any optimization of tariff consumption, they really paid a lot. However, the situation has changed significantly in recent years. Modern electric boilers such as Buderus Dakon Daline PTE 4 kW or the more powerful versions with outputs of 6, 8, 14 and 18 kW can, in combination with the right tariff, heat accumulation and modern regulation, operate with surprisingly reasonable operating costs. The goal of this article is to go through the entire topic from the basics – that is, from how the distribution tariffs for electric heating are set, through practical boiler settings, to concrete examples of savings that we see in practice.
Distribution tariffs for electric heating in Slovakia – the basic understanding you need
Before you start any optimization, you need to understand the system of distribution tariffs. In Slovakia, tariffs for households with electric heating are managed by ÚRSO (Office for the Regulation of Network Industries) and are distributed through the respective distributor – ZSE, SSE or VSE depending on where you live. Tariffs for electric heating are labeled as DD5, DD6, DD7 (or historically TDD5, TDD6, TDD7) and are designed to allow electricity consumption in multiple bands with different prices – that is, in the so-called low tariff (NT) and high tariff (VT).
The basic principle is simple: the distributor will allow you to consume heating at a discounted electricity price during the night and possibly also during the day in specified hours, based on the approved technical equipment (i.e., an electric boiler recognized for the tariff group). In return, the distributor imposes requirements on the installed power and type of equipment. Boilers of the Daline PTE series are suitable for these tariffs – this is discussed in more detail in the article Connection and installation of the Daline PTE electric boiler – procedure and installation requirements.
Difference between NT and VT – in numbers
For an average household on tariff D1 (standard household without a night tariff), you pay around 0.20–0.27 €/kWh for electricity in 2024, including all fees. When switching to the heating tariff group DD5 or DD6, you get:
- Low tariff (NT): the price of electricity typically drops to 0.09–0.13 €/kWh
- High tariff (VT): the price is similar to or slightly higher than D1
- Monthly fee for reserved power increases with higher circuit breaker capacities
The key parameter is therefore how many hours per day your boiler runs in NT. The more thermal energy you can store in an accumulator (tank) during NT, the cheaper you will heat during VT – when the boiler does not run or runs only minimally.
Tariff DD5, DD6 and DD7 – what distinguishes them
DD5 is intended for combined electric heating – that is, when you have electric heating as a supplementary source alongside another one (e.g., heat pump + electric boiler as a backup). NT usually lasts 8 hours a day.
DD6 is the most common tariff for direct electric heating. NT lasts at least 8 hours, in practice distributors offer 12–16 hours of NT spread across multiple blocks (typically 0–6h, 10–14h, 22–24h).
DD7 refers to accumulation electric heating (e.g., storage heaters, or a boiler with a large accumulation tank). NT lasts up to 20 hours a day. The condition is sufficient accumulation capacity (installed tank volume for heat) and that the device is capable of covering the daily demand with accumulated energy.
For Daline PTE boilers, the most commonly used tariff is DD6, or DD7 in combination with a large accumulation tank (500–1 000 liters). Always check the exact conditions directly with the distributor – each has slightly different technical and administrative requirements.
Accumulation tank as the basis for savings – how it works in practice
The electric boiler itself – whether it is Buderus Dakon Daline PTE 8 kW or the more powerful 18 kW model – is only one part of the whole system. The real potential for savings is unlocked when you connect it to an accumulation tank (heat storage). This tank functions as a "thermal battery" – the boiler charges it during NT (when electricity is cheap), and this accumulated energy then covers the heat demand during VT (when electricity is expensive) without the boiler having to operate.
In practice, it looks like this: in a house with a heat consumption of 15,000 kWh per year (a typical family house of 120–150 m²), the boiler operates most of the night hours during the cold heating season. If your tank is large enough (e.g., 500 liters), the boiler will charge it to a temperature of 70–75 °C within 8 hours of NT. This energy covers most of the daily consumption. Result: 70–85 % of electricity consumption is drawn during NT. With a price difference between NT and PT of 0.10 €/kWh and an annual consumption of 15,000 kWh, this represents a savings of 1,050–1,275 € per year compared to drawing the entire consumption during PT. This is not theory – these are the numbers we see in practice with customers who have properly set up the system.
How many liters of tank do you need?
There is a simple approximate calculation: for each kW of installed boiler power, calculate 30–50 liters of tank volume. For the Daline PTE 14 kW, this means a tank of 420–700 liters. In practice, 500-liter tanks are most commonly installed for 10–14 kW and 750–1,000-liter tanks for 18 kW. It also depends on the heat loss of the house and the length of your distributor's NT period. This topic is discussed in more detail in the article Connecting the Daline PTE boiler to an accumulator tank or floor heating.
Installed boiler power and its impact on the tariff
The distributor considers not only the type of boiler but also its installed power when approving the tariff group. Certain minimum power requirements must be met to qualify for a favorable heating tariff. A general rule states that the power of the electric heating must be sufficient to cover the total heat demand of the house (projected thermal power).
For specific examples: a house with a heat loss of 6 kW requires a boiler with a minimum power of 6 kW. In Slovakia, for older houses (before 1990) without insulation, a heat loss of 80–100 W/m² is assumed, for insulated houses 40–60 W/m², and for low-energy buildings 20–30 W/m². For a 150 m² house with a loss of 50 W/m², the required power is 7.5 kW – the Daline PTE 8 kW is therefore suitable. How to precisely choose the boiler power is described in detail in the article What power of Daline PTE electric boiler do I need for my house?.
Setting up the Daline PTE boiler for maximum savings – step by step
The Daline PTE boiler is equipped with a built-in timer and a thermostat input, which are two basic tools for tariff-optimized heating. Proper setup makes a big difference in practice.
1. Setting the time program according to NT blocks
The first step is to find out from your distributor the exact NT times. They are not universal – ZSE, SSE, and VSE may have slightly different blocks. Once you know them, set the boiler's time program (or an external thermostat/controller) so that the boiler actively operates precisely during NT. During PT, the boiler either does not heat at all (if the accumulator tank covers the need), or heats only to a maintenance temperature (e.g., 18 °C instead of 22 °C).
2. Equirthermal regulation – automatic adjustment of power to outdoor temperature
The Daline PTE boilers can be equipped with an equithermal regulation with an external temperature sensor. The principle is simple: the colder it is outside, the higher the water temperature the boiler prepares. This eliminates overheating during transitional periods (spring, autumn), when the boiler without equithermal would unnecessarily heat to 70 °C, even though it would be enough to have 45 °C when it is 5 °C outside. The result is direct energy savings. More about equithermal setup and other regulation functions can be found in the article Control and regulation of the Buderus Dakon Daline PTE boiler – setup and programming.
3. Thermostat hysteresis setting
Setting the thermostat hysteresis (by how many degrees the temperature can drop below the setpoint before the boiler turns on again) directly affects the switching frequency and thus the boiler wear and efficiency. Too small hysteresis (0.5 °C) = frequent short cycles, unnecessary wear. Too large hysteresis (3 °C and more) = slight discomfort due to temperature fluctuations. The optimal is hysteresis of 1–1.5 °C.
4. Night (reduction) mode
Reducing the temperature in rooms during the night or during absence is another tool for savings. Lowering the temperature from 21 °C to 17–18 °C for 8 night hours reduces daily heat consumption by 10–15 %. Note: the reduction must be synchronized with the NT block. If NT is at night (e.g., 22:00–6:00), the boiler will work during this time anyway – instead of heating the room, it will charge the tank. The night reduction mode in the room does not limit the tank charging at night, provided the system is properly connected and regulated.
Practical examples of savings from real customer cases
Theory is one thing, practice is another. Here are a few anonymized examples that illustrate real numbers.
Example 1: Family house 140 m², older, partially insulated, Western Slovakia (ZSE)
The house had a heat loss of about 9 kW. The customer switched from a gas boiler to an electric Daline PTE 14 kW with a 500-liter accumulator tank. Tariff DD6 from ZSE (12 hours of NT). Annual electricity consumption for heating: 16,800 kWh. Share of NT: 78 %. Average electricity price per kWh (blended): 0.128 €. Annual heating costs: about 2,150 €. Before switching to gas (at the gas price in that year), the customer paid about 2,600 €. Savings of about 450 € per year, plus the cost of servicing the gas boiler (100–150 €/year) was also eliminated.
Example 2: New construction 120 m², low-energy, Central Slovakia (SSE)
House with heat loss 4.8 kW. Boiler Daline PTE 6 kW with 300-liter buffer tank + floor heating. Tariff DD7 (20 hours NT). Annual consumption for heating: 7,200 kWh. Share of NT: 93 %. Average price: 0.099 €/kWh. Annual costs: approx. 713 €. This is a result that will surprise many – heating a modern 120 m² house for less than 60 € per month on average throughout the year.
Example 3: Older villa 220 m², combined system – boiler + backup
The customer wanted to keep the gas boiler as the main source and the electric boiler Daline PTE 18 kW as a backup and additional source for transitional periods (spring/autumn), when the gas boiler is oversized and inefficient. Solution: at outside temperature above +5 °C, only the electric boiler heats from DD5 (8 hours NT), buffer tank 750 liters. At lower temperatures, the gas boiler is turned on. Savings compared to gas heating throughout the year: approx. 600–800 € annually.
Steps to change tariff – step by step
One of the most common questions from customers is: how to practically switch to a heating tariff group? It is not complicated, but you need to follow the correct procedure.
Step 1: Energy audit / calculation of house heat loss. The distributor will require proof that your electric boiler is sufficiently powerful to meet the demand. This can be a project documentation, energy certificate or a report from an authorized designer.
Step 2: Selection and installation of the boiler and buffer tank. The boiler must have the appropriate certification. Daline PTE boilers are certified for these purposes. The electrical installation must be carried out by an authorized electrician and the whole system must be inspected.
Step 3: Request for tariff change from the distributor. You submit the request with an attachment – installation inspection report, boiler specification sheet and possibly a heat loss calculation. The distributor evaluates the request, usually within 30 days.
Step 4: Installation of HDO (remote mass control). The distributor installs or activates the HDO receiver, which controls the switching of NT. The boiler (or external contactor) must be connected in such a way that it responds to the HDO signal.
Step 5: Setup and test operation. After activating the tariff, you set up the boiler, timer and regulation. We recommend monitoring consumption and tank temperature for the first 2–3 weeks and possibly adjusting the settings. The installation process and technical requirements for installation are described in more detail in the article Connection and installation of the Daline PTE electric boiler – procedure and installation requirements.
HDO – what it is and why it is important for the boiler
HDO (Hromadné Diaľkové Ovládanie) is a system through which the distributor sends a signal via the power grid to activate or deactivate NT. This signal controls a contact (relay) that switches or stops the heating device. It is a one-way control from the distributor's side – the customer cannot bypass or change it.
For the Daline PTE boiler, this means that if you are on a tariff with HDO, the boiler must be connected in such a way that it responds to the HDO signal – either by direct connection to the HDO contact or via an external controller that receives the HDO signal. If the boiler runs outside the HDO signal in HT, the distributor cannot technically stop it (the boiler runs on normal power), but you pay the HT price for electricity. Therefore, correct installation and programming of the timer is crucial – the boiler should not heat intensively in HT, only if it is necessary (strong frost, when the buffer is not sufficient).
Other factors that affect the operating cost of electric heating
Insulation of the house
This is the most effective investment – and it applies to every heat source, not just electric. A house with a heat loss of 50 W/m² consumes half the energy in the season under the same conditions as a house with a loss of 100 W/m². For an electric boiler, this directly means half the costs. Investment in insulation (façade, roof, windows) pays off much faster with electric heating than with gas, because electricity is a more expensive energy carrier in HT and energy savings directly translate into a lower bill.
Type of heating system
Floor heating works with low water temperature (30–45 °C) and is ideal for an electric boiler with a buffer tank. A radiator system requires a higher temperature (55–70 °C), which means a higher temperature potential in the tank, greater tank heat losses and slightly lower overall efficiency. This does not mean that radiators and an electric boiler do not work well – they do, but you should make sure that the tank has sufficient capacity and insulation.
Correct boiler sizing
An oversized boiler is a waste – an unnecessarily high power input means a higher monthly fee for the reserved power. An undersized boiler cannot cover the heating demand and you will have to intensively heat even during the off-peak period (VT). Correct sizing is fundamental – that is why we recommend always starting with a heat loss calculation, not with an estimate. More about choosing the right power can be found in the article How to choose an electric boiler Buderus Dakon Daline PTE – what to pay attention to.
Proper insulation of pipes and the storage tank
A heat storage tank located in an unheated boiler room or garage loses 10–20 % of the stored energy through the tank walls. Quality insulation of the tank and pipes (at least 50 mm of mineral wool or equivalent) is a low-cost investment with a quick return on investment.
Electric boiler vs. heat pump – where is the line of profitability
This question is often asked. The answer depends on several factors. A heat pump has a much higher COP (coefficient of performance) – typically 3–5 kWh of heat for 1 kWh of electricity. An electric boiler has COP=1 (100 % efficiency, but without multiplication). At first glance, the heat pump clearly wins. In practice, it is more complicated:
- Investment costs: An air-to-water heat pump costs 6,000–15,000 €, a ground-to-water heat pump 12,000–22,000 €. An electric Daline PTE boiler of 8 kW costs up to 600 €, 18 kW up to 1,200 €.
- Lifespan and maintenance: A heat pump has moving parts (compressor), maintenance requirements, and a higher risk of failure. An electric boiler is practically maintenance-free.
- Backup: In the case of a heat pump failure (compressor breakdown), you are left without heat. An electric boiler can be an inexpensive backup for a heat pump.
- Suitability of the environment: An air-to-water heat pump loses efficiency in heavy frost (below -15 °C), precisely when you need heat the most. An electric boiler operates equally reliably in all weather conditions.
Conclusion: for the construction of a low-energy house with a long-term perspective, a heat pump is more investmentally advantageous. For renovation, backup or supplementary source, small houses and cottages, or as a temporary solution – the electric Daline PTE boiler with the DD6/DD7 tariff is practical and economically sound.
Common mistakes customers make – and how to avoid them
Over the years of working with electric boilers, we have seen several recurring mistakes that drastically increase operating costs:
- Too small a storage tank: A 200-liter tank with a 14 kW boiler is not enough to accumulate enough heat for the whole day. Result: the boiler runs even during the off-peak period (VT), the system's payback decreases.
- No regulation according to the NT: The boiler runs 24/7 regardless of the tariff – the customer has the DD6 tariff group, but the boiler does not distinguish between NT and VT. The entire consumption is billed at an average rate instead of being optimized for NT.
- Setting the storage tank temperature too high: A tank temperature of 85–90 °C increases heat losses from the tank and pipes. The optimal temperature is 70–75 °C, even less for floor heating.
- Ignoring seasonality: During the transitional period (October, April), it is not necessary to charge the tank to maximum every night. A boiler with good regulation should be able to adapt – and if it cannot, the settings should be manually adjusted according to current temperatures.
- Wrong circuit breaker/reserved power: An 18 kW boiler requires three-phase power and the corresponding circuit breaker (3×32 A). If the house has a 3×25 A circuit breaker, the boiler cannot operate at full power. This must be resolved before installation.
Return on investment in the Daline PTE boiler
The purchase price of the Daline PTE electric boiler is very low compared to other heat sources. A boiler with a power of 6–8 kW costs 400–600 €, with a power of 14–18 kW 800–1,200 €. Installation including electrical connection and inspection: 300–800 € depending on the complexity. An accumulation tank of 500 liters with accessories: 600–1,200 €. Total investment for an average family house: 1,500–3,500 €.
For comparison: a new condensing gas boiler including installation costs 2,500–5,000 €, a heat pump 8,000–20,000 €. If an electric boiler with accumulation saves 1,000 €/year compared to direct electric heating without NT, or 400–600 €/year compared to gas, the return on investment is 2–5 years. That is an excellent result.
Most frequently asked questions (FAQ)
Do I need approval from the distributor to install the Daline PTE electric boiler?
You do not need approval from the distributor for the installation of the electric boiler itself – a revision report from a certified electrician is sufficient. Approval from the distributor is required to change the tariff group (switching to DD5/DD6/DD7). Without this change, you can operate the boiler, but you will pay the standard D1 tariff without the NT benefits. Therefore, assigning the correct tariff group is economically crucial and should be part of the planning from the beginning.
How many hours a day does the boiler run during NT in a typical 120 m² house?
In cold winter (outside temperature -5 to -15 °C), the boiler may run for the entire NT block (8–12 hours) at full power to accumulate enough heat in the tank. In the transitional period (outside temperature 0 to +8 °C), the boiler runs for 3–6 hours during NT, the tank fills up sooner and the boiler is turned off. The regulator with the tank thermostat controls this automatically. It is important that the boiler does not run longer than 1–2 hours a day during the off-peak period (only to catch up, when the tank cools down).
Can I operate the Daline PTE boiler on a single-phase network?
Boilers up to 3.5 kW are commonly single-phase (230 V). Daline PTE boilers with a power of 6 kW and above are three-phase (400 V, 3×16 A for 6 kW, 3×25 A for 14 kW, 3×32 A for 18 kW). If your house has a single-phase connection, it must be expanded before installing a three-phase boiler. This is ensured by your electrician in cooperation with the distributor.
What happens if the tank cools down during the day in the off-peak period and it is -10 °C outside?
The boiler will automatically turn on during the off-peak period to maintain the minimum temperature in the rooms. This is a necessary backup and it is normal for the boiler to operate outside of NT during strong frost. The goal of optimization is not zero consumption during the off-peak period, but its minimization. If this happens too often, the tank is likely too small or the boiler is undersized – the system configuration should be reconsidered.
Can the Daline PTE boiler be controlled by a smartphone or via the internet?
The Daline PTE boiler does not have a built-in WiFi module or internet interface by default. However, it is possible to connect it via an external smart thermostat or controller (e.g., Siemens RDE, Honeywell T6R, etc.) with WiFi and an app. This allows remote monitoring and changing of settings. Details are in the article Regulation and control of the Buderus Dakon Daline PTE boiler – setup and programming.
Is electric heating ecological?
It depends on the source of electricity. If your electricity comes from renewable sources (or you buy green electricity), CO₂ emissions are zero – which is a better result than natural gas or propane. In Slovakia, there is still a significant share of coal in the electricity grid, so the overall carbon footprint depends on the energy mix. The advantage is that electric devices can automatically benefit from the increasing share of renewable sources – without changing the equipment. A gas boiler will burn gas even in 20 years, while an electric boiler will operate on an increasingly cleaner electricity grid.
Conclusion – electric boiler Daline PTE and tariff: when does it really make sense
Electric heating using Daline PTE boilers makes economic sense when three basic conditions are met: correctly sized boiler power, assigned heating tariff group (DD5/DD6/DD7), and an accumulation tank with sufficient capacity. When these three elements work together, electric heating can compete with gas and in some cases even surpass it – without a compressor, refrigerant, chimney, and annual service checks.
Choosing the right model is important – for a small apartment or a low-energy house, the Daline PTE 6 kW is sufficient, while for a larger family house with higher heat loss, you should consider the 14 kW model or 18 kW. Always start with a heat loss calculation – not a guess from the neighbor. And if you are unsure about certain details, take a look at other articles in this Knowledge Center, where individual topics – from choosing the power, through installation and regulation, to service – are discussed in detail.
Do you have a question about this topic?
Having trouble deciding or dealing with a specific situation in your household? Write to us – we are happy to help.