Generally speaking, a nitro helicopter is heavier than one built from the ground up for electric flight. The main reason being that nitro engines vibrate considerably more than an electric engine. Because of this, a nitro helicopter has to be built more robustly compared to an electric model to make sure the vibrations don't physically stress the helicopter in a negative way.

Case in point, my .50 size T-rex 600 is lighter than my e-converted Century Hawk Pro which is a .30.
Now, depending on what you're doing, I would not rule out conversion all together depending on what components you decide to go with.

The main benefit (and main headache) of doing nitro to electric conversions is that with electric, you have a huge choice in motors, and you can tailor your power to anywhere from mild scale like flight, to ballistic power that would put any nitro engine out there to shame.
The trick is trying to figure out what motor, gear and voltage combination will work for your conversion. Generally, a nitro engine revs higher than an electric motor simply by design (that's not to say you can't get an electric motor to rev as high as a nitro engine, but most motors in the size range you need for a helicopter conversion have lower rpm since they generate more torque this way). Because of that, gearing changes are usually necessary, but it's entirely dependent on the model in question.

Theres nothing that says you have to go out and spend $200 on a speed controller and $200 on a motor unless you're obsessed with having best of the best and top brand names. There is a lot of good chinese imports that are significantly cheaper than a lot of the more popular and very expensive brand names. Obviously, as with anything, you get what you pay for most of the time, and though imports may not be totally lacking in quality (indeed, some of it is quite good for its price), but if something goes wrong, you usually have no manufacturer to stand behind the product for warranty issues. So you do take some risks.

When I converted my Hawk Pro, I only spent $120 on the power system ($60 motor, $60 ESC). With the setup I used I was even able to use the default clutch bell as the main gear, I simply adapted it to fit on the motors shaft. RPM is not as high on the head as I would like, and a bigger main gear would solve that, but I can't find any that will fit with the hawk pro, which means I either need a hotter motor or more voltage. Obviously, there are more suitable motors for not much more than what I paid, I simply chose what was available to me at the time at the lowest possible price (this was a bit of an experiment on my part to prove it was possible). Works like a charm, see the video link at the end of my post.

The main cost for any electric setup is, of course, the batteries. You need roughly 6 cells to put a .30 size nitro conversion into the air (due to weight). I think the big mistake a lot of guys do is they go out and buy a single 6 cell pack. Here's the problem, if you crash, or if you damage the pack in any way, you're out a single $200 battery. I would personally suggest to buy 2 high capacity (e.g 4000+ mAh) 3 cell packs and connect them in series instead of one 6 cell pack. The benefit of this is that if you happen to damage one pack, you're only out 3 cells instead of a full 6 cell pack, your overall costs will be lower should you need to replace a battery.

The obvious disadvantage is that you need to charge 2 separate packs for a single flight. A bit more of a hassle, but if you've been in electric flight for awhile you'll realize it's unavoidable. By using smaller packs you also have the benefit of being able to use those same batteries in smaller models or planes that don't need 6 cells. The other thing is with electric, your average flight time will only be about 6 to 8 minutes on 4400 packs, shorter than you'd get on a nitro machine.

Not including other standard electronics (servos, gyro, etc.) it only cost me about $300 to convert my hawk pro to electric power. This isn't a powerhouse setup, but I didn't want that for the hawk anyways (it's certainly no 3D machine, that's what I got the t-rex 600 for ). But it does fly quite well on such a modest setup and would be great for a scale ship.


In the end, it comes down to what you want. I only converted a Hawk Pro as something to do, I knew it wouldn't be a powerhouse simply because of it's weight. If you want a good flying, good performing electric model, you're better off buying one designed specifically for electric flight. Easier to work with, less hassle to adapt motors, better power to weight ratios, etc.
If you just want to convert a nitro ship to electric for the hell of it (I love to tinker personally ), it can be done, and for not as much as most would have you believe, it just depends on how much performance you want and how much you're willing to shell out for it .

Below is a video of the very first flight after my conversion on my hawk pro. Keep in mind nothing at all had been trimmed at this point on the model (that's why the tail is all over the place). I was flying in -15 weather at the time (which is why I did not bother fixing the tail till it's nicer out, gyros don't like cold weather, no sense in trimming it in the cold and then having to re-trim it once warm weather got here). Anyways, enough excuses, here's the link:
http://www.truenorthernhobbies.com/m...lightfeb16.avi


To answer your final question, do I think it's cost effective to convert nitro to electric? No, not really. If you want stick banging 3D performance, electric, while considerably more powerful than a nitro helicopter, will cost you considerably more upfront. And at the rates that we deplete our lithium batteries, you're lucky if you see over 100 cycles, so I don't even think that the electric over the long run is cheaper than nitro argument really applies either.