The Baxi boiler efficiency calculator

Discover fantastic fuel savings with the Baxi boiler efficiency calculator

The Baxi boiler efficiency calculator is here, helping you to discover how much could potentially be saved on fuel bills by fitting a new, A rated, boiler in comparison to an existing boiler.

Quick and easy to use, if you want to know how to reduce fuel consumption, gas bills and carbon emissions, our boiler efficiency calculator can show the actual savings made possible by installing an energy efficient boiler

Key features of Baxi A rated boilers:

  • Extremely efficient and reliable
  • Nationwide support from heateam - our award winning, dedicated, support service
  • Variety of boiler types and numerous outputs available for different size properties and requirements, all with the same great quality.
  • Compatible with a wide range of accessories

The Baxi boiler efficiency calculator will ask for general information about the property in question and the current heating system. It takes just a few minutes to answer the questions that will help us to predict fuel usage and calculate savings.

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Terms & conditions

Boiler Efficiency Calculator - Online

It's important to note, in calculating your energy use that the Baxi efficiency calculator has made a number of assumptions based on your home and current heating type, such as the number of people living in your home and the efficiency of your current heating system. For details of the assumptions made please email

Baxi cannot be held liable for any decisions or actions you may take on the basis of information contained in the calculator. The outcome is not an official Energy Performance Certificate or a Green Deal Assessment and is intended to be used only as a guideline to the fuel savings you could potentially achieve.

Boiler Efficiency Calculator - Printed version

The Baxi boiler efficiency calculator is designed to provide you with an indication of the potential savings on your gas bill that can be achieved by replacing your old boiler with a new high-efficiency boiler.
It does not take into account other savings that can be achieved through improvements in controls or building fabric improvements, nor does it take into consideration an individual's change in usage or any fluctuation in gas price. The savings stated are based on your current gas bill, your dwelling's heat and hot water demand and the efficiency of your current boiler.

The fuel bill used in this calculation is based on the gas used for heating and hot water. It is assumed that 83%* of your total energy bill is used for heating and hot water.
Gas price used is 0.036 £/kWh* of gas. The efficiency percentage is calculated using the midpoint for each of the SEDBUK 2005 bands as shown below.

Band  Efficiency band   Mid point
 Band A  90% and above  91.1%
 Band B  86% - 90%  88%
 Band C  82% - 86%  84%
 Band D  78% - 82%  80%
 Band E  74% -78%  76%
 Band F  70% - 74%  72%
 Band G  Below 70%  65%

The saving is based on replacing the current boiler with a Band A rated boiler at 91.1% efficiency from SEDBUK 2005 data.

Example calculation:
Homeowner fuel bill for gas used on heating/hot water is £1,100 with a gas price of 0.036 £/kWh* of gas
1.  To find out how much gas is used for heating/hot water in the dwelling, divide the heating/hot water gas bill (£1100) by the unit cost per£/kWh of gas (0.036):
2.  A Band G boiler (65% efficient) is converting only 65% of the gas used for heat/hot water into usable energy. (65% of 30,556 kWh = 19,861kWh) This now shows the heat/hot 
     water demand requiring 19,861kWh of usable energy
3.  By dividing the amount of usable energy required as calculated in step 2 (19,861) by the efficiency rating of your new Band A  boiler (91.1%), you get the new total amount of gas
     used for heat/hot water in the dwelling when using a Band A boiler. (19,861/0.911 = 21801kWh)
4.  To work out the cost of the new usable energy amount as calculated in step 3, multiply the new figure by the unit cost per £/kWh of gas. (21801 x 0.036 = 784.83)
5.  To calculate your saving, subtract the new total from your current gas bill (£1100 - £784.85 = £315.15)
For full details of the calculation please call us on 0800 138 3142.

*Source: DECC

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