Hi Annie,
We find that the Alde system is by far the best we have had in a van,had it in our last 2 vans and when we renew we will certainly be looking for a van with Alde,in answer to your question ,when it is extremely cold and you first arrive on site yes gas and electric together for a short time til the temp gets up then turn off the gas and run on electric, we caravan all year round and as we allways have the heating on low at home during the colder months we never use gas at all,as the van is usually still relatively warm when we arrive on site.
Baza