Seat arona and auxiliary heating

Hello, Although the winter is almost over now but with such things you can deal with all year round. Although I have nothing against scratching or freezing the first 2km. (But I already have But I wanted to treat my arona to a stand heating alone to avoid cold starts. At the same time, the company Defa came across that already for quite a long time motor preheater builds. Of course a normal version of eberspächer or webasto are location-independent systems. But unfortunately also with with offers of 1800€ + In addition, the plants consume fuel which would be a bit annoying with me with Cng but understandable because otherwise it remains cold. But the plant only works if no reserve is on. And with only 9 liters is almost half already reserve on the tank clock. The Defa system would cost completely 340€ at with. I have a 230v socket both outside as well as in the garage and on the work also. The oil we heated by means of contact plate. According to reports r I guess that’s for 40-60 degrees of oil. So the rest of it isn’t far, and it just comes out warm air. What do you think? Does anyone have any experience with Tgi and heating?