I am trying to create a model of refrigeration having the energy consumption and the temperature over time. So far, I've tried regression but fitting this data into linear model seems impossible. Another thing that I've tried is cross correlation but it's insignificant (around 0.11 at lag 0). I also clustered the data and for another fridge I was able to state that if the fridge is in 'idle mode' (e.g. not consuming electricity) the temperature goes above certain value. However, for this fridge, this doesn't work as the data seems pretty random. Here is a scatter plot of the data, the bigger the circle, the higher the frequency.
Any ideas what type of analysis can I use to derive insights from this? I would like to know if there is any correlation between the kW data and the temperature data. A new plot for the full duration that I have: