Simple Guide Calculating Heating KW or BTU Per Room and reduce Co2.

Simple Guide for Calculating Heating KW Per Room.
IntelliHeat step-by-step method, how to buy the right size & power Electric Radiators for each room.

Choosing your new or replacement heating system is stressful enough, without worrying about how to choose the correct size of Electric Radiator for every room. Perhaps you have chosen a 1,5 KW radiator and you are now wondering if it is enough to heat your size of each room? If is the correct dimensions, or perhaps you have rooms of an average 12 square meter size and need to know the correct output you need to heat each room.

Online Heating KW Calculator

A quick internet search will show you many online calculators to use, but guess what? They are ALL DIFFERENT. They all ask different questions, request different measurements and ask you to confirm different basic parameters. So which one will give you the right answer? Will they all give the same answer? How can you decide which one to trust with the comfort of your whole family for the next ten years?

Electric Radiators Direct Heat Transfer

Electric Heating Calculator Algorithm

Every online radiator size calculator is just an algorithm that will give you an average-ball-park calculation if you live in an average house. But does an average house have cavity wall insulation? Double glazing? Floor insulation? Loft insulation? semi detached property? And are you SURE that you live in an average house? Is there a specification for what they deem to be average?

Suppose you live in an apartment with a flat below or above. Will the answer be the same? Can the algorithm know how many forms of heat loss are in each of your rooms? If your room sizes are the same, will the KW output needs of each radiator be the same – without knowing how many doors and windows are in each separate room?

Room Size minus causes of heat loss

There are many causes of heat loss that MUST be considered for EVERY ROOM, and an online calculator MUST ask about all of them, to be able to give you an accurate KW electric radiator size.

Here is a list of the causes of heat loss which should be considered:

  • Size of area to be heated (in meters) including the Length, Width, and Height: Single, Double or Triple Glazing and whether it is wood, metal or PUVC.
  • Insulation method of cavity walls, Loft and Floor.
  • Number of internal and external doors, the number of windows with opening lights.
  • Construction of the walls
  • Age of the property, when it was built
  • Hight of the ceilings.
  • Total window area in square meters.
  • Numbers of outside walls.
  • Property level (floor).
  • Is it a single-story building? Postal code location.
  • What type – and how much – roof insulation is present.
  • The construction of the floor and the underfloor construction.
  • The average external temperature and the thermal zone of your town or city (which is very different for Scotland, coastal towns, inner cities, and rural villages).
  • Which rooms have a north-facing, exterior wall?
  • Your personal bespoke heating requirement.
  • Planning for a zonal heating system must start early because the system depends on the efficiency of the building shell and the floor plan.

Heating load calculations for a well insulated property built after 1976 are based on a requirement for 35/45 watts per M2 . These heat loads take into account the specific U values provided for each exercise and has been produced as a conservative estimate due to variable geographical emplacement of the properties.

Any online calculator that DOESN’T include all these parameters, is only giving you an approximate guide, and NOT an accurate and reliable answer.  Or would you prefer advice, from an experienced electric heating expert?

Overheating your home is illegal 

The problem with an ‘approximate’ heat calculation done online, is the risk of overpowering the heating needed for each room. Just one extra radiator per room can add hundreds to the cost, which is bad for you – but good for the shop online who will then sell MORE radiators. 

The precise calculation of heat required for your home is regulated by the SAP 2012 legislation (The Standard Assessment Procedure for the Energy Rating of Dwellings SAP), making it illegal to install MORE heating KWs than you need. Saving your money, saving wasted energy and saving the planet.  It is like buying a Tiger Tank to mow the lawn! Average modern homes will need around 10KW of heating, so why would you want to install a 35KW boiler? Always speak to an experienced heating company before you buy more than you need online. Otherwise, when you sell your property, you won’t get a good Energy Performance Certificate.

This legislation means that lower carbon factors in SAP will change the heating design.  SAP is used to assess energy use and carbon emissions for Building Regulation Approved Document L in domestic buildings, while SBEM is the equivalent tool for non-domestic buildings. Reduced data SAP (RdSAP) is used to produce Energy Performance Certificates. Full details are on this link:

IntelliHeat Provides FREE Expert Consultation

Using the IntelliHeat heating calculations is only half of what we do every day for our customers. The calculations will give you a high-level guide size, which can then be turned into ACCURATE ADVICE from a quick and easy phone call to our resident heating calculation expert. A real person who is available during working hours to speak to you about your heating needs, guidance within the different radiators ranges, your specific property issues and the individual requirements of your family members. 

Be wary of the cheap as chips heaters sold online, with no UK address or recognised company or phone number in this country. Sorting out a problem with a Chinese importer will be very difficult next month, or next winter.

When you phone us at IntelliHeat; there’s no need for you to calculate ‘degree days’ or Kilowatt Hours, as we do it all for you, and we can then refer you to one of our local IntelliHeat qualified, trained and autorised Installers, who can install your chosen radiators with no fuss or bother. 

intelli-heat- electric-heating-Zoning
intelli-heat- electric-heating-Zoning

Conclusion summary

  1. Never rely on an online approximate calculation for the comfort of your family. You are more likely to be charged for more radiators than you actually need.
  2. Speak to the manufacturer or an experienced heating consultant to calculate your precise requirement of BTU (British Thermal Units) or KWH (Kilo Watt Hours) to comply with Building Regulations, save energy and reduce your heating bills.
  3. Always use a company, (preferably a manufacturer) you can SPEAK TO on the phone because anyone can sell anything online, and if it doesn’t arrive, doesn’t work, or develops a fault in 2 months’ time, you will always be able to solve any problem.

    To enable us to assist you with your query as efficiently as possible, please call us on 0203 916 0000. We will not send out a sales representative or bother you with unwanted phone calls.

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