Vertical-external-cavity surface-emitting lasers (VECSELs) have received much attention in the scientific community by accessing a broad spectral range, and enabling efficient intra-cavity frequency mixing [1-3]. They combine the high output power of semiconductor diode lasers with the superior beam quality inherent to surface emitters. The majority of the applications relies on the high output power of the device . Generally, the performance of the VECSEL is limited by overheating. Efficient cooling concepts are therefore inevitable providing distribution and removal of the excess heat. A careful choice of the pump profile is also considered crucial for the optimal output characteristics. Here, we study the impact of the size and spatial fluence distribution of the pump spot on the output power. For this purpose the input-output characteristics of the device is monitored while simultaneously tracking the temperature in the active region.