PHAM NEWS | OCTOBER 2026 ElectricHeating 33


Accurate calculation is the foundation of every successful project


Accurate heating requirement calculations remain central to good electric heating specifi cation, helping installers recommend the right products, avoid sizing mistakes and ultimately ensure user comfort and effi ciency. Yulia Gillingham, head of marketing at Dimplex, explains more.


I


n practice, a heating requirement isn’t just a number to calculate; it’s a way to understand how the room performs.


By looking at how quickly the space loses heat, how much energy it takes to bring it back to the desired temperature, and what it takes to maintain comfort, installers can build a clearer picture of what the specifi cation needs to achieve. Those answers may depend on familiar factors, but each needs careful consideration, because if something is missed or one assumption carries too much weight, the fi nal sizing can quickly lose touch with what the room needs. Room volume is the obvious


starting point, because length, width and height all aff ect the amount of air the system has to warm. Two rooms with the same fl oor area can still need diff erent heating levels if one has a higher ceiling, as the calculation must account for the whole space rather than just the fl oor footprint. Insulation is often where the


biggest diff erence lies between otherwise similar properties, with loft, wall and fl oor insulation all infl uencing how well a room holds heat once warmed up. A well-insulated room will usually need less input than an identical room with poor insulation, so any fabric upgrade, whether a loft top-up, cavity wall fi ll or replacement glazing, should prompt a fresh calculation. Windows and doors are


consistently weak points in a room’s thermal envelope. Glazed area, glazing type and condition all infl uence heat loss, with large or ageing single-glazed windows a particular liability and external doors adding further loss. External wall exposure


matters too, as a room bordered by other heated spaces generally needs less heating input than a similarly sized


 The Dimplex Heating Calculator enables accurate calculations for different types of applications and can recommend solutions on a room-by - room basis


room with external walls exposed to wind and weather. A corner room with two external walls, for example, will typically lose more heat than an equivalent internal room. Desired room temperature


Yulia Gillingham Head of marketing at Dimplex


and usage patterns also matter, because a home offi ce used constantly during the day will place diff erent demands on a heating system than a bedroom used mainly overnight. As a guide, most living areas sit between 18–21°C, while UK government advice recommends heating homes to at least 18°C in winter, particularly for older occupants or those with health conditions.


Whichever electric heating type is chosen, both oversizing and undersizing have


consequences


The right fi gures A manual assessment is still possible by establishing room volume, applying an appropriate wattage-per-cubic-metre fi gure for the insulation standard and factoring in the desired temperature rise. While useful for understanding what drives the number, it remains an approximation, particularly where irregular room shapes, mixed construction types or older building fabric make the answer harder to judge with confi dence.


That is where a good calculator earns its keep and


Dimplex, with more than 75 years in electric heating, off ers a free online Heating Calculator that asks for details such as room type, dimensions, wall length, window and door area, glazing type and the construction of the fl oor, roof and walls. From there, it estimates the required heat output and suggests suitable products, helping users move from basic assessment to heater selection. Designed for single- room projects, it is used by homeowners, landlords and installers, with hundreds of users each month. For trade professionals


working at scale, we’ve taken the idea further through exclusive sizing and specifi cation resources for our PRO Installer Club Partner members. The free trade loyalty programme gives registered installers perks and support, but its real value is practical tools that save time at the design stage. The Advanced Heating


Calculator is built for professionals, helping them size integrated heating systems room by room, produce recommendations that support comfort and effi ciency as well as handle complex assessments, including projects eligible for ECO funding. Users can also create single-


or multi-property projects with customer-ready proposals and personalised branding. Meanwhile, installers and specifi ers working on even more complex projects can access direct support from our Applications Design team, who will be able to assist with system design, product selection and technical guidance.


The right specifi cation Once the required heat output is determined, the conversation can move from calculation to product choice, with the right answer shaped by the property, the energy tariff and how the room is used. The right product


specifi cation diff ers from project to project – and even room to room. For example, homes with access to off -peak electricity tariff s are often well suited to high-heat-retention (HHR) storage heaters, such as the Quantum range, which store lower-cost energy for release throughout the day. In other scenarios, direct- acting options such as electric radiators and panel heaters may be a better fi t, off ering responsive, on-demand heat with programmable controls suited to changing occupancy patterns. Whichever electric


heating type is chosen, both oversizing and undersizing have consequences. An oversized unit can mean unnecessary upfront cost and aff ect operating effi ciency. In contrast, an undersized unit can leave the room struggling to reach temperature and increase running costs as it works harder for longer. Getting the heating requirement right fi rst helps avoid both problems. On a busy project, it can be


tempting to treat the heating calculation as a quick admin step, but it is where comfort, effi ciency and customer confi dence are either protected or put at risk. However you decide to make those calculations, the principle is the same - every good electric heating installation starts with getting the heat requirement right. ◼ phamnews.co.uk/1026/67


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