In every Canadian and U.S. commercial and industrial zone, window security grills are the main security prevention products present. From my own experience, I estimate that I have participated in installing grills at over 2,000 clients .... almost all of them in commercial and industrial areas.
This experience has given me a unique perspective in evaluating the effectiveness of steel grills on windows. In a nutshell, the sad fact is that window security grills serve a minimal ..... and I mean a bare minimal ..... effectiveness against determined burglars.
The worse place to put a window security grill is on the outside. (see above photo). Whenever I met a client who had window security grills on the outside, and who wanted more on an addition to his place of business, I was always successful in changing his mind to not install grills like this by simply taking my hand-drill and removing the bolts that were holding his grills up. This usually took me less than a minute.
Bolt cutters, electric saws, or simply putting a chain around the grills and having it attached to the hitch of your truck will also be effective in ripping out this grills in less than a minute. Oh yeah .... because the alarm is inside not outside, it will not even be activated.
The best way to install window security grills is in the inside. This forces burglars to break the glass thereby activating the glass break detectors for the alarm to go off. The burglar(s) will still be able to get into your premises within one to two minutes, but depending on how good is your alarm and/or police response this saving of extra time could mean a significant saving in product or computers stolen. The burglars are on the clock. The longer that they are on outside the shorter in time they will be inside.
One added advantage of having window security grills on your windows, is that if your neighbor does not, it is more than likely that the criminals will attack him first.