Thinking to get an oil column heater to heat up a small study area. I think a 1000w unit is sufficient, but a larger unit is more flexible at a higher cost.
In terms of running cost, to heat the same area up to similar temperature, does large unit costs more or about the same?
It all depends on the power rating.
I think cheapest is Gas heater < oil column heater < fans heater is the most expensive to run.
Cost is just another way around.