In the last decades, pollutant emissions from burning fossil fuels have become of great public concern due to their impact on health and the environment. For this reason, strict legislations have come into force worldwide, which obligate to reduce these emissions. For heating devices such as boilers, it has been realized that these emissions’ reduction could be effectively done with the concept of lean premixed combustion. However, lean premixed combustion technology is more vulnerable to the interactions with system acoustics, which brings a negative side effect: Thermoacoustic instabilities. Thermoacoustic instabilities occur from the feedback loop between the heat release and the acoustic waves in the complete system. They can lead to unwanted noise, flame extinction and, in extreme cases, structural damages. In domestic boilers, these instabilities show themselves as loud noise and flame extinction. In order to eliminate thermoacoustic instabilities in domestic boilers, the trial and error method is used commonly, which requires significant amount of effort and time. Therefore, the researches are focussing on predicting these instabilities at the early stages, where the flame characterization is an important part of the prediction of the thermoacoustic instabilities. In this study, the flame characterization of the burners used in domestic gas boilers is done experimentally. The Flame Transfer Function method is employed, which is a popular approach for the characterization of the flame response to acoustic perturbations. First, an experimental setup is built, where the velocity fluctuations of the fuel/air mixture and the heat release fluctuations from the flame could be measured. Then, the effects of different parameters, i.e. equivalence ratio, gas quality, perturbation amplitude and burner type on the flame response are investigated.