Сombi boiler efficiency guideline

Сombi boiler efficiency guideline

What boiler efficiency is

The basic formula of combi boiler efficiency deals with input/output ratio. In other words, to calculate it you need to compare the amount of heat it generates to the amount of energy it uses to accomplish this task. Thus, the higher the ration is, the more efficiently an appliance transfers energy to heat and the less energy it misspends.

Heating systems with condensing gas boilers are much more energy efficient than with non-condensing units. For example, the first ones have got the input\output ratio of 89% and higher. On the contrary, the figures of the second ones are much modest and vary from 75 to 80%. Moreover, the situation with old gas and oil appliances is even worse as they waste 35-45 % of burned fuel. That is to say, these old devices transfer only 65-55 % of used energy to heat.

It is worth to mention the most energy efficient heating systems are with electric units. Their input\output ratio reaches 100%. However, they are still too expensive to be as popular as gas heating appliances.


Factors speaking for the need to increase energy efficiency

The question of energy efficient heating system arises due to following factors:

  • Global concerns with safeguard the environment and climate changes,
  • Ever rising prices on fuel.

The first factor reflects care for the environment by carbon emission reduction. Above all, it reads that a gas boiler is environment-friendly if it has high efficiency. To clarify, it has lower carbon emission. In addition, it doesn’t misspend exhaustible natural resources

The second factor speaks of your budget. For example, with 70% system efficiency you waste 30% of your energy bills. It is about 4 times more in comparison to 92% ratio. In other words, if you are running such a low efficient heating appliance, you pay up to 25% more than you could with 92% ratio.


How to know how much fuel efficient your boiler is

One of the simplest ways is to check a label on the unit. Each heating device has got an efficiency rating. However, we should clarify one aspect about the ratings.

The case is all units after 2015 year have got ErP ratings from G to A+++. However, units manufactured before 2015 year have got SEDUK ratings with slightly different figures. ErP is European Union regulation that replaced SEDUK in 2015.

If you want to know how to match the ratings in letter with percentage input/output ratio, look at the following table:


Efficiency ratings in letter Efficiency in percentage
A+++ 98 – 100%
A++ 95 – 98%
A+ 92 – 95%
A 90 – 92%
B 86 – 90%
C 82 – 86%
D 78 – 82%
E 74 – 78%
F 70 – 74%
G <70 %


How to choose energy saving boiler

This task has become easier due to recent changes in legislation. Today, by the law, gas and oil heating appliances may be manufactured and sold in the UK only if its efficiency is 92% and more. Therefore, all modern units are condensing. So, speaking of gas and oil heating appliance, now you need to make choice only between 92 – 98% rated units.

Besides, this legislation also affects boiler installation when it concerns gas and oil units.

At Harrogate plumbers we have got vast experience in dealing with different heating systems in Leeds and all around. So, this enables us to make a list of popular, energy efficient, and reliable boilers for homes. For your convenience we marked input/output ratio in brackets:

  1. Viessmann Vitodens 200-W / 100-W (98%),
  2. Viessmann Vitodens 100-W (98%),
  3. Worcester Bosch Greenstar 36CDi Compact (94%),
  4. Vaillant EcoTEC Exclusive Green IQ 835 (94%),
  5. Vokera Evolve C 24kW (94%).

We recommend you to choose one of these units. However, we also recommend you to pay attention to their prices/efficiency ratio also, as the most efficient models usually are the most expensive.

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