Welltherm consumption and costs: calculations for your space

Electrical power indicates energy drawn per unit of time when the panel heats at that output. Convert watts to kilowatts by dividing by one thousand. A 710 W panel therefore has power of 0.710 kW. If it heats continuously for one hour, it uses 0.710 kWh. For several panels, add their outputs insofar as you assess the same period and active operating duration.

The example formula is: energy in kWh = power in kW × actual hours switched on. Calculate that energy’s costs using kWh × tariff per kWh. Take a hypothetical €0.30 per kWh tariff. The 710 W panel then costs 0.710 × €0.30 = €0.213 for one uninterrupted heating hour. That is just over 21 cents. This amount applies to that calculation hour under those assumptions, not automatically every hour you occupy the room.

The distinction between occupancy and operating time matters. You may spend eight hours in a study while the thermostat activates the panel for part of that time. Alternatively, you may warm a cold room over a shorter period with the installation active for much of it. Therefore do not list the entire usage period as active heating time without substantiation. A thermostat programme indicates when heat may be available; it does not inherently report how many minutes the receiver actually switched.

Suppose a plan includes two 710 W panels. Combined power is 1.420 kW. At three actual operating hours, example consumption is 4.260 kWh. With the hypothetical €0.30 per kWh tariff, energy costs are €1.278 that day. If panels operate at different times or for different durations, calculate each separately. Then add their energy or costs.

Preferably calculate different scenarios. A few-active-hours scenario shows brief-use implications. A second with longer heating reveals consequences of greater heat demand. This gives a range for your plan’s assumptions. That range is not yet a winter prediction. Assessing reality requires monitoring usage, building and weather conditions and testing assumptions against measurements.

If you work five days weekly under precisely these assumptions, calculated weekly use is 5 × 4.260 = 21.300 kWh. At the hypothetical €0.30 per kWh tariff, that is €6.39. The example includes no heating outside those working days and no other appliances. If absent for two days or active time changes with weather, re-enter assumptions. Do not multiply such an example week by every week in a year without further assessment. Seasons, holidays and changing usage can substantially alter reality.

A room loses heat to its surroundings. The loss depends partly on the building envelope, glazing, ventilation, adjoining rooms and outdoor temperature difference. Panel output must fit the application’s heat demand. Square metres alone provide insufficient information. A room beneath an uninsulated roof may respond differently from a similarly sized room in a better-insulated part of a home.

Required connected output and final energy consumption are different questions. First determine whether the installation delivers enough warmth for the desired situation. Then determine how often that capacity is needed. An adequately powered installation need not operate continuously at full capacity. An undersized one may stay on for long periods without delivering desired comfort. Lower wattage alone therefore does not prove lower costs for equivalent heating performance.

Starting temperature and adjoining-room usage also matter. A room warming after prolonged absence starts differently from one already at a background temperature. Open connections to other building areas can change demand. Describe these conditions when comparing consumption with another period. Otherwise a kWh difference may incorrectly be attributed solely to a changed thermostat setting.

A warm panel radiates heat to people and surfaces within range. Heat transfer to air and warming the surroundings also play roles. Air temperature does not necessarily rise immediately after activation. Therefore note perceived comfort at the occupied position and how the room develops when comparing. Lowest consumption is not a useful result if the space is unsuitable for its intended use.

Positioning affects experience. A panel behind a cupboard or where the desired seat lies outside its range may feel different from a suitable arrangement. Therefore look beyond set temperature when investigating a usage problem. Also discuss mounting position, obstacles and capacity relative to heat demand. Specific model instructions determine usable mounting options.

Start with a clear measurement boundary. Do you want consumption for one panel, all panels in a zone or the complete building? A total electricity meter also includes lighting, cooking and other appliances. This does not make its data worthless, but panel use cannot be derived without further information. Use measurement suitable for the relevant connection and load. For a fixed installation, have an expert assess options.

Keep a simple log with date, room used, active period, temperature settings and measured energy. Also note unusual circumstances such as a cold start, extra ventilation, open doors or changed work schedule. Add a brief comfort note. After changing a setting, you can then identify other simultaneous changes. This helps interpret a difference without immediately presenting it as a general system saving.

Preferably change one relevant setting at a time in a trial. First match the time programme to actual occupancy, for example, then observe the result. Simultaneously changing programme, temperature and room usage makes the cause less clear. Comparing two days with very different weather also requires care. Several comparable periods provide more information than one isolated day. Use results to refine your plan, not promise a fixed percentage for other homes.

Check the documentation for the meaning of a thermostat or app figure. An amount may be calculated from entered output, configured hourly price or registered operating time. This differs from an independent measurement of consumed kWh. Some settings must also match the combined output of paired panels. Incorrect input then gives an inaccurate indication even when controls otherwise work normally.

Use an indication in a cost overview when its assumptions are known. Mark such figures as calculated in your own overview. Record measured energy separately. You can then compare a device display with actual measurement later and investigate differences. A menu name or euro symbol alone does not prove the device knows your current electricity contract or all installation costs.

A fair comparison uses the same heated space, comparable conditions and similar comfort. Include the existing heating that remains operating. With electric supplementary heating, the panel may consume additional energy while another installation remains active. The question is then total consumption and comfort of that combination. Do not count all existing heating costs as avoided without measurement.

Direct electric heating converts electricity into warmth. For this resistance system, heat production is approximately one kWh of heat per kWh of electricity. A heat pump also uses environmental heat. Its delivered-heat-to-electricity ratio can therefore be greater. Actual performance depends on installation and conditions. Do not compare these systems by electricity price alone or only electrical appliance output.

A hypothetical calculation explains the difference. For a 3 kWh heat demand, a direct electric system uses approximately 3 kWh of electricity in the simplified example. A heat pump with an assumed performance ratio of 3 would use about 1 kWh of electricity. That ratio is a calculation assumption here, not a guarantee for an appliance or home. Purchase, installation, separate-zone use and required comfort also remain part of the overall assessment.

Ask which components a proposal includes. Consider panels, brackets or frames, selected controls, receivers and connection-point preparation. Discuss any electrical work separately. A quotation missing necessary components may look lower on paper but is not an equivalent comparison. Also assess service and future extension options. Prices for your products and version follow the specific proposal.

Define the total-cost period beforehand. An annual comparison and one over several years answer different questions. Longer periods require assumptions about tariffs, usage and possible adjustments. Keep those assumptions visible. Avoid an exact payback amount when supporting details are missing. Purchase costs plus different usage scenarios often provide a more useful overview.

Make each room’s heating programme recognisable. For a study, use actual working times; for a guest room, actual occupancy. Discuss an appropriate background temperature while empty. Include the building, moisture exposure and other heating. A setting working for one well-insulated room is not automatically suitable for every other space.

With separate zone controls, identify which panels belong to each zone. One room’s schedule must not inadvertently affect another. Keep an overview of paired appliances and settings. This clarifies changes and helps service enquiries. Controls support considered operation; selected appliances and heat demand determine the actual options in your installation.

Consider your own solar electricity within the energy overview, but availability does not automatically coincide with heat demand. When panels consume power, your production may be lower or absent. Any cost assessment must therefore match your measurements and contract. Solar panels do not automatically make electric heating free or change a room’s required output.

Send dimensions, ceiling height and insulation and glazing information. State existing heating and whether you seek primary or supplementary warmth. A floor plan and photos help discuss mounting positions and separate zones. Note usage times and desired controls. If consumption data is available, state whether it is panel measurements, calculated indications or whole-building data.

For an existing installation, add article numbers and current settings. Explain especially what you want to improve: insufficient comfort, unclear consumption, another working week or an extra room. We can then address the enquiry at the right level. Sometimes investigation starts with a usage programme; elsewhere capacity or positioning needs attention first. One higher or lower thermostat figure is not the same solution for every situation.

We help relate product selection, output and controls to your own usage. View our infrared panel range and discuss a quotation for your space to determine the suitable version. Keep cost-calculation assumptions with the proposal. After commissioning, you can measure specifically, assess settings and test the plan against reality.