There are warm up cycles that engines have to go through. The longer the amount of time you spend warming up the more fuel you consume.

On cold days and long idles (supposing you're in Baguio) you would need less thermal rejection to keep your engine running swimmingly.

Also those fans can draw anything form 10A to 30A. Calculate the amount of power you use and that will translate to fuel consumption.

Add the fact that the wear and tear of high draw electric motors will have on your battery.

Costs will, however miniscule they can be -incrementally accrue.