Completely your choice, but here’s a few things to consider. Ultimately it depends on how dirty your windows are. For regular cleans, say every couple of months, you can usually skip the inside every second time. However, if it has been several months or more since the last clean, we recommend that both the external and internal glass be cleaned. The outside usually has a lot of dust, insect marks and bird deposits, whereas inside will have grease, mould and grime… in fact we often find that the inside is equally as dirty as the outside!