Speech sounds serve the function of distinguishing meaning. However, in German, schwa sometimes has no such semantic function and is optional in certain cases, like first-person singular inflectional suffixes. Nonetheless, this optionality has not yet led to a total removal, or obligation to articulate, schwa in these suffixes. The present study investigates the effects of phonetic context and stress on schwa optionality. The data set consists of two registers, formal and informal, of German spoken in Germany and Namibian German. The following speech sound and the stress of the following syllable, which are thought to affect the likelihood of word-final schwa production, were analysed for 44 speakers using Praat. Significant effects were found for stress, with less schwa productions before unstressed syllables. Significantly less schwa instances were observed before vowels. Overall, register had a significant effect, with more schwa productions in the formal condition. The impact of stress and the effect of register were more marked in the subset of Namibian German. These findings highlight the importance of investigating the interaction of phonetic features and register and emphasise the value of exploring different varieties in the study of speech production phenomena.