Analyses of wind turbine performance from high-alpine installations are not scarce. We presentcharacteristics of the power-curve from large and a small wind turbine installations. On-sitedata from one small wind turbine on a mountain shoulder close to the Lukmanierpass and fivelarge wind turbines on the Gotthardpass is combined with LiDAR data, to analyse the influence ofturbulence intensity, temperature and snowcover on wind turbine performance. These conditionsare known to strongly vary in alpine environments and to be different from typical installationsat low elevations. Based on observations, we aim to explain the seasonal characteristics and toverify the viability of mountainous regions for wind energy production. We confirm apositive influence of highly turbulent winds at low wind speeds and show that the effect becomesnegative at high wind speeds. At low wind speed, a very high turbulence intensity (>0.4) allowseven to counterbalance the effects of low air density. In this regard, small wind turbines profitmost, as winds tend to be more turbulent close to the ground due to terrain effects. On thecontrary, at high wind speed, it needs a very low turbulence intensity (<0.1) to keep the highestpossible power-output. For this, large wind turbines are better suited, as winds higher up are lessturbulent. Both low temperature and the presence of snow are found to have a positive influenceon wind turbine performance, especially for small ones. A combination of increased air densityand atmospheric stability at low temperature explains this result. Snow is typically present at lowsurface temperatures and may smooth the terrain. The small wind turbine is foundto particularly benefit from these conditions, as they impact the wind flow over a larger part ofthe rotor area, whereas the effects are less marked for large wind turbines.