When I started up Muir Engineering the only tool I knew about for development of electrical engineering plans was AutoCAD. Well, and Microsoft Visio, which is fairly handy for schematics and block diagrams and such, but not very good for drawing up a building electrical plan.
I didn't realize until much later than this approach is pretty weak. The problem is that AutoCAD doesn't know a thing about electrical engineering! It has no clue that the block I just put down represents an receptacle. It doesn't know anything about panelboards, circuits. So, while the process of creating building electrical plans with AutoCAD is faster and more flexible than doing it on paper, it really isn't any different, in the same way that writing a letter using Microsoft Word, and writing one by hand use basically the same process. Sure, one can go back and correct mistakes, it is a lot easier to re-use content, and the spell check is pretty handy (especially for us engineering types, we are infamous for our lousy spelling), but it is still writing.
Then in early 2014 I learned about the MEP version of AutoCAD. MEP stands for "Mechanical, Electrical, and Plumbing". (I don't care much about the M and the P, but the E is pretty important around here!).
The software has a library of devices (and I've created a ton of new ones), and each device can have a set of properties. So, all of a sudden instead of a block representing a receptacle, I can drop down a device that is a receptacle, and that device can be configured for a certain VA load, and it can be connected to a circuit. Other entities the software knows about include panels, mechanical equipment, light fixtures and such.
The other really important piece of the puzzle is automatic scheduling. I used to build up schedules by hand, but with MEP the schedules are automated. This has saved me a lot of time and improved the accuracy of the drawings.
The problem I have now with AutoCAD MEP is that it is a bit of an orphan. I don't think AutoCAD has many developers assigned to new features. The AutoCAD MEP forum is a bit of a wasteland, and many of my postings go unanswered. It has some crazy and inconsistent behaviors, and it is a bit crash prone. I think AutoDesk has abandoned this product but won't admit that.
Just an aside, there is a product called AutoCAD Electrical. That sounds like something an electrical engineer would be interested in, right? Well, it turns out that that software is for detailed control system schematics, and isn't at all relevant to the kind of work I take on.
In 2015 I'll consider moving up to Revit but that looks like a major commitment, both in terms of time and money.