Calculating the hourly energy consumption of a water pump is the basis for a reliable assessment of the operating costs of the installation. Regardless of whether you are designing a new home installation, you choose circulation pump for central heatingwhether you are verifying the efficiency of an existing hydrodynamic system - precise calculations will allow you to avoid overpaying for electricity and choose a device with optimal parameters. In this article, we will guide you through the entire process: from base formulas, through factors influencing annual energy consumption, to the specificity of individual types of pumps from the Dambat offer - IBO and brands IPRO.
Energy basics – what is the power consumed by the pump?
Each electric pump draws electricity from the grid, expressed in watts (W) or kilowatts (kW). The result of the calculation is kWh of energy consumption by the pump in a given time period. This absorbed power is not the same as hydraulic (useful) power - it describes the difference between them pump efficiency (η), defined as the ratio of hydraulic power to electrical power drawn from the network. For typical water pumps, the efficiency ranges from 30 to 80%, depending on the class of the device, its operating point and the degree of wear.
Energy consumption expressed in kWh of electricity we calculate with a simple formula (the result is kWh of energy consumption downloaded from the Internet):
where: E – energy consumed from the network, P – power consumed by the pump (from the nameplate), t – operating time in hours
Example: a circulation pump with a power of P = 0.09 kW (90 W), operating for 12 hours a day, will consume per day: E = 0.09 kW × 12 h = 1.08 kWh of electricity. On a monthly basis (30 days), this means approximately 32.4 kWh, and annually - nearly 395 kWh. This is a specific item in the electricity bill.
Rated power and actual power consumption
The manufacturer states this on the nameplate rated power (or input power) which corresponds to full load operation. In practice, installers should remember that actual power consumption depends on operating point pumps on the Q-H characteristic. When the pump operates at a lower flow or higher pressure than its rating, its power may be higher or lower than declared.
It plays an important role here inverter (inverter). Inverters from the Dambat offer allow for smooth regulation of the rotor speed, adjusting the power consumption to the momentary flow demand. In practice, this is achieved lower energy consumption even by 30-50% compared to systems operating at constant speed. This is especially important in installations where the flow is variable - e.g. in water supply networks of small buildings or hot water circulation systems.
Hourly and daily pattern - table of sample IBO pump powers/IPRO
Below we present approximate data for selected types of pumps from the Dambat portfolio. The operating time is an example and should be adjusted to the actual operating schedule.
| Pump type | Rated power [kW] | kWh/h | kWh / day (8 h) | Annual energy consumption (3650 h) |
|---|---|---|---|---|
| IBO energy-saving circulation pump (class A) | 0,05–0,15 | 0,05–0,15 | 0,40–1,20 | 183–548 kWh |
| IBO hot water circulation pump | 0,03–0,08 | 0,03–0,08 | 0,24–0,64 | 110–292 kWh |
| IBO surface pump (home) | 0,37–0,75 | 0,37–0,75 | 2,96–6,00 | 1350–2738 kWh |
| Submersible pump IPRO 4" | 0,37–2,20 | 0,37–2,20 | 2,96–17,60 | 1350–8030 kWh |
| submersible pump IBO (for dirty water) | 0,37–1,10 | 0,37–1,10 | 2,96–8,80 | 1350–4015 kWh |
| Submersible pump IPRO 6" | 2,20–11,0 | 2,20–11,0 | 17,60–88,0 | 8030–40 150 kWh |
The data in the table above are indicative. Detailed parameters of each device can be found in the catalog cards available on the website dambat.pl – catalogs for download.
Seasonal energy consumption – why does the work schedule matter?
Annual i seasonal electricity consumption by the pump rarely results solely from multiplying the power by 8760 hours. In fact, circulation pumps for central heating they operate mainly during the heating season (approx. 1,800–2,400 h/year in Poland), DHW circulation pumps can operate 24 hours a day with interruptions resulting from the controller, and deep-well pumps operate in impulses - only when opening the draw-off points or filling the hydrophore tank.
Therefore, seasonal energy consumption is calculated separately for each operating period. This is professionally done using the degree-hour method or based on a detailed energy analysis of the building. Seasonal pattern:
where f_load – actual load factor (typically 0.5–0.9 for central heating circulation pumps)
In the case of energy class A circulation pumps (EEI ≤ 0.23), the current consumption in the season is usually 50-70% lower than in classic pumps with an asynchronous motor. For installers and designers, this is a key argument when selecting devices - both in terms of meeting ErP standards and real benefits for the investor.
EEI, energy classes and Ep - what do the numbers say?
The European ErP (Energy-related Products) directive forced manufacturers to mark the energy efficiency of circulation pumps using an indicator EEI (Energy Efficiency Index). The lower the EEI, the more energy efficient the pump is. Since 2015, only pumps with EEI ≤ 0.23 can be offered on the market. In practice, modern circulation pumps with EC (electronically commutated) motors achieve an EEI of less than 0.15.
It is equally important in the context of the building's energy performance EP index (indicator of demand for non-renewable primary energy), expressed in kWh/(m²·year). It describes how much energy from non-renewable sources is needed to cover the building's annual needs for heating, ventilation, cooling and hot water preparation. The lower this value, the better - the building meets the requirements of the WT 2021 technical conditions, which set a limit of ≤ 70 kWh/(m²·year) for new single-family houses.
An energy-efficient circulation pump has a direct impact on the calculated EP index. The use of an energy-saving IBO class A pump can reduce this value by several points - which in practice may determine whether the building obtains energy class A or B. This also applies to building's heat demand expressed in kWh/(m²·year), which is the basis for determining the Ep index.
The building's energy demand - how does the pump fit into the balance sheet?
Building demand for electricity is the sum of the demand of all devices: lighting, household appliances, HVAC systems and pumps. In a typical single-family building thermal energy demand is covered by a boiler, heat pump or electric heating, while circulation and circulation pumps constitute auxilium - auxiliary devices, the consumption of which is sometimes omitted in simplified analyses.
Meanwhile, in buildings with extensive installations (e.g. underfloor heating + domestic hot water + radiator heating), the total building demand for electricity to power pumps may exceed 600–900 kWh/year. This is comparable to the annual consumption of a washing machine or dishwasher. Precise calculations are therefore necessary both in the installation design process and when verifying operating costs.
It is also worth remembering about building energy efficiency as a whole. Thermal insulation of the building directly affects the length of the heating season and, consequently, the operating time of circulation pumps. Good insulation shortens the operating time of the pump, lowering seasonal energy consumption and real electricity bill. On the other hand, better insulated buildings allow for use of a low-temperature installation (e.g. underfloor heating with parameters 35/28°C), which significantly reduces thermal energy demand generated by a heat source.
Heat pump COP and annual electricity consumption
In heat pump installations, the electricity consumption of the water pump (circulation or submersible) must be analyzed in the context of COP (Coefficient Of Performance) – energy efficiency coefficient of the heat pump. COP (Coefficient Of Performance) determines how many units of thermal energy the device provides for each unit of electricity consumed. Typical COP values are 3.0–5.0 for ground source heat pumps and 2.5–4.5 for air source heat pumps.
However, the COP provided by the manufacturer applies to the heat pump unit itself. The annual energy consumption of the entire system also includes: circulation pump in the primary circuit (glycol/brine), pump in the secondary circuit (central heating), DHW circulation pump, controllers and valves. The total total auxiliary electricity consumption can be 400-900 kWh, which can reduce the actual system SCOP (Seasonal COP) by 0.2-0.5 points from the catalog value.
That is why the selection of energy-saving auxiliary pumps - such as the series of energy-saving IBO circulation pumps - has a real impact on the overall energy balance of the heating system. In installations with using a low-temperature installation (underfloor, fan-coile) it is possible to set the pumps to lower pressure and flow parameters, which further reduces power consumption and reduces the operating costs of the installation.
Average annual consumption and energy efficiency – how to measure and improve it?
Average annual consumption energy by the pumping installation is calculated as the sum of seasonal energy consumption, increased by the consumption in standby mode (for controllers and electric valves). Measurements can be carried out using energy meters installed directly in the switchboard or using built-in meters available in modern controllers and inverters.
Energy efficiency of the building in the context of pump systems, it is improved primarily by:
- Selection of the pump to the actual operating point – avoiding oversizing, which leads to valve throttling and energy loss.
- Application of the inverter – smooth regulation of rotational speed eliminates unnecessary power consumption with variable flow demand. Dambat inverters are compatible with IBO i submersible and surface pumps IPRO.
- Regular maintenance – scale deposits and corrosion increase flow resistance, which results in higher energy consumption with the same hydraulic performance.
- Thermal insulation of pipelines – reducing heat loss from joints and straight sections building's heat demand and shortens the operating time of circulation pumps.
- Drivers with a daily schedule – limiting the pump operation to the actual hours of demand reduces seasonal electricity consumption without compromising comfort.
It is available on the Dambat website energy savings calculator, which allows you to quickly compare the power consumption of the old and new circulation pump. This is a good tool for presenting the profitability of replacing a device to the end customer.
Energy audit and pump selection – what should the installer know?
Energy audit building is a formal analysis of energy consumption, ending with thermal modernization recommendations. One of the elements of the audit is the assessment of pumping systems - both from a technical and energy perspective. The installer or designer cooperating with the auditor should provide data on:
- types and powers of installed pumps,
- device operation schedule (h/year),
- actual operating point in the installation (Q and H),
- energy class of circulation pumps (EEI),
- control means used (inverter, controller, valves).
Based on this data, audit analysis allows for precise calculations annual energy consumption by the pump installation and indicate specific savings resulting from replacing the devices with newer models. It is worth taking advantage of the opportunities they offer Dambat controllers and automation systems – record working time and alarms, which makes it easier to collect data for analysis.
Filters, valves and pressure gauges – the impact of accessories on the energy balance
The pump itself is only one element of the installation. Filters, valves and pressure gauges influence flow resistance and, therefore, indirectly affect the energy consumed by the pump. Dirty filter causes an additional pressure drop that the pump must overcome - this higher energy consumption with the same water flow. Regular replacement of filter cartridges is therefore not only a matter of water quality, but also the energy efficiency of the system. Energy efficiency of the building it starts with taking care of every element of the installation - not only the insulation or windows, but also the plumbing equipment.
Pressure gauges pumps installed on the suction and discharge sides allow for ongoing monitoring of the operating point and early detection of filter clogging or impeller wear. Dambat pressure gauges are available in various pressure ranges and accuracy classes - choose the appropriate one for the operating pressure of the installation. In turn non-return and anti-contamination valves they protect the pump against backflow of the medium, which prevents hydraulic shocks and increases the durability of mechanical seals.
Selection of a pump for the installation – practical tips for the installer
Correct pump selection requires knowledge of several key installation parameters:
- Required flow (Q) [m³/h or l/s] – resulting from the heat demand, the number of water intake points or the well capacity.
- Required lifting height (H) [m liquid column] – the sum of linear and local losses in the pipeline plus the geometric difference in levels.
- Medium temperature – circulation pumps for central heating they must be adapted to the temperature of the heating medium (up to 110°C for most IBO models).
- Tightness class and medium resistance – for clean water, contaminated water, sewage.
- Energy class required – especially important for low-energy and passive buildings, where EP index may not exceed statutory limits.
Dambat's offer includes complete IBO pumps, IBO ITALY i IPRO – from circulation pumps with a power of 30 W, through multi-stage deep well pumps up to 11 kW, to industrial units exceeding 15 kW. You can make your own selection using converters available at dambat.pl, or contact the manufacturer's technical department.
Submersible pumps IPRO – electricity consumption in well intakes
Submersible pumps IPRO 4", 6" and 8" series are devices intended for permanent operation in conditions of pumping water from drilled wells. Their annual energy consumption depends on the well flow, the depth of the water table, the length of the pipe column and the working flow. For a small household (Q = 1–2 m³/h, H = 40–60 m) a typical 4" pump IPRO with a power of 0.55-0.75 kW will work in impulses - a total of approx. 500-1000 h/year, which translates into annual energy consumption of the order of 275–750 kWh.
In sets with an inverter (e.g. Dambat sets with inverter) the pump runs smoothly, maintaining constant pressure without water hammer. This means not only lower power consumption, but also longer durability of the column of pipes, fittings and valves. Installers in the well industry know well the problem of the so-called "water hammer" - the inverter effectively eliminates it, especially at greater installation depths.
Circulation and circulation pumps - energy classes and EEI
IBO energy-saving circulation pumps The ECM (Electronic Commutation Motor) series are devices that meet and exceed the requirements of the ErP 622/2012 regulation. They are characterized by an EEI below 0.20, and the best models achieve an EEI < 0.15. For the installer this means that average annual consumption energy through the circulation pump can be limited to 50-150 kWh/year - many times less than in the case of older models with asynchronous motors.
They constitute a separate group DHW circulation pumps. Their task is to maintain continuous circulation of hot water in the circulation pipes, which eliminates the need to wait for hot water at the taps. Although the power of these devices is low (15-50 W), they usually operate around the clock or according to a schedule - their annual electricity consumption may amount to 130-440 kWh/year. The use of a controller with a timer and a temperature sensor allows you to reduce the working time and achieve realistic results lower energy consumption by 30–40%.
A detailed offer of IBO circulation and circulation pumps can be found on the website dambat.pl – circulation pumps and accessories.
Summary – how to calculate the hourly power consumption of the pump in practice?
The hourly electricity consumption of a water pump is the product of the rated power (or actual power absorbed) and the operating time. However, the complete analysis also includes: the operating point on the Q-H characteristic, hydraulic and mechanical efficiency, the influence of medium temperature, the condition of filters and valves, and in the case of installations with an inverter - the load profile over time. On this basis it can be determined annual energy consumption, include them in the calculation of the building's energy index and assess the profitability of replacing the device.
Careful analysis helps improve building energy efficiency as a whole. The Dambat company not only supplies high-quality pumps of the IBO and brand brands IPRO, but also calculation tools, technical catalogs and technical department support. Take advantage of the resources available at dambat.plto select the optimal pump both in terms of hydraulics and energy - and enjoy an installation that works effectively for years.
FAQ – Frequently asked questions of installers and specialists
How to calculate the kWh of energy consumption of a submersible pump per hour?
The formula is simple: E [kWh] = P [kW] × t [h]. Example: submersible pump IPRO 4" with a power of P = 0.75 kW, working for 1 hour, will consume 0.75 kWh of electricity consumption. Assuming impulse operation (approx. 2 h/day), the daily kWh of energy consumption will be 1.5. Always use the power given on the nameplate or in the technical data sheet - not hydraulic power or shaft power, because these values are lower than the actual consumption from the network.
What is the Ep index and how does the pump affect its value?
The Ep index (primary energy indicator) is an indicator of the demand for non-renewable primary energy, expressed in kWh/(m²·year). The WT 2021 regulations set a limit of Ep ≤ 70 kWh/(m²·year) for new single-family houses. Energy-consuming pumps - especially circulation pumps with low efficiency - increase EP index. Replacing it with an energy-saving IBO pump of EEI < 0.20 class can reduce this indicator by 2–5 kWh/(m²·year), which is crucial for obtaining the building's energy class A or B.
What is the seasonal electricity consumption of the DHW circulation pump?
A 25 W hot water circulation pump operating 16 h/day for 365 days will consume 0.025 kW × 16 h × 365 = 146 kWh/year, i.e. 146 kWh of electricity. The use of a controller with a schedule (e.g. only in the morning and evening, a total of 6 h/day) will reduce consumption to approximately 55 kWh/year - savings of up to 60%. IBO circulation pumps with a built-in timer and temperature sensor do this automatically, without additional equipment.
Does the inverter really reduce the energy consumption of the pump?
Yes – and significantly. The power consumed by the pump is proportional to third power rotational speed (law of similarity). This means that reducing the rotational speed by 20% reduces power consumption by approximately 49%. In practice, in installations with variable flow demand, the inverter allows to achieve lower energy consumption by 30–55% compared to a pump operating at constant speed with valve throttling. Dambat inverters are available as modules dedicated to IBO i submersible pumps IPRO.
How does the building's thermal insulation affect the operation of circulation pumps?
Thermal insulation of the building directly shortens the heating season - in a well-insulated passive building it is approximately 1,200-1,600 h/year, and in old, uninsulated buildings even 3,500 h/year. With the same circulation pump with a power of 100 W, the difference in annual energy consumption is: 100 W × (3500–1400) h = 210 kWh/year. In addition, better insulation allows use of a low-temperature installation and selecting a pump with lower pressure parameters - which further reduces power consumption.
What does COP of a heat pump mean and how to take it into account in the calculations?
COP (Coefficient Of Performance) is the ratio of thermal energy produced to electricity consumed. COP = 4.0 means that for every 1 kWh of consumed electricity, the heat pump provides 4 kWh of heat. In calculations annual energy consumption system with a heat pump, we take into account SCOP (seasonal COP), which is an average value for the entire heating season. The balance should include auxiliary energy: circulation pumps, controllers, valves - which actually reduces the efficiency of the system by 5-15%.
How does an energy audit help when selecting pumps?
Energy audit provides data about the real the building's heat demand and electricity consumption by auxiliary systems. On this basis, the installer can precisely select the circulation pump for the required hydraulic parameters (Q and H), calculate the expected energy consumption in a year and indicate savings resulting from replacing devices. An oversized or undersized pump always means higher energy consumption and faster mechanical wear.
What pump parameters should be included in the building's energy performance?
The building's energy performance (EE) includes the electrical power of circulation and circulation pumps and the estimated time of their operation in the season. For class A circulation pumps with EEI < 0.20, the power in nominal conditions from the catalog card and the seasonal operation time in accordance with the installation design are assumed. EP index calculated on this basis must meet the requirements of WT 2021. Dambat drivers they record operating time and alarms, which facilitates retrospective verification of calculation assumptions.
Does lower energy consumption translate into a shorter return on investment in a new pump?
Yes. A simple example: an old circulation pump with a power of 80 W vs. new energy-saving IBO with a power of 25 W. Power consumption difference: 55 W. At 3000 h/year of the heating season lower energy consumption is 55 W × 3000 h = 165 kWh/year. At an energy price of PLN 0.80/kWh, the savings amount to PLN 132/year. The cost of a new energy-saving IBO pump is approximately PLN 400-700 - the return on investment will be achieved after 3-5 years. Average annual consumption energy by the new class A pump is up to four times lower than in the case of older models.
