I doubt I will get one but I have recently thought about it being a part of a stable of bikes.

If I did get one it I would only want to use the battery on only 5-10 percent of the time so I would want it to be rather on the light side as E-Bikes go. What are some of the lightest E-Bikes around? If I want it to be light would I be better of building one from an existing regular bike frame?

If you want a light bike you're going to need to wait a year or two, or look at Chas58's threads and DIY.

Faraday Pourter (sp?) perhaps.

I'm very happy with my Stromer ST-1. It's not light, but with assist it feels light ;> It's still a workout, but it cuts my commute time by enough to allow for 4+ days of commuting.

Checkout local dealers, take long test rides.

Here's an ebike kit I purchased a month ago. This combo weighs 9.8 pounds. If I subtract the weight of wheel, rim, spokes, it will add 7.8-8.0 pounds to the rear of your bike, and you have to use a freewheel. I included the handle bar levers, but I forgot to put in the LCD display, so it evens out.

A battery will weigh anywhere between 4-9 pounds. Maybe more if you get a bigger one.

So it depends on your donor bike. My lightest one is 46 pounds with battery. As this is a geared motor with very little drag, it rolls/pedals reasonably well by my standards. Someone with a 20 pound bike would disagree.

DW, only eight or so pounds plus battery is pretty impressive. Luna mighty mini and my 21 pound Zaskar and the result should be <35 pounds. Maybe next project after the one in progress.

My old 24v 250w bike is 26kgs but it has an old-tech battery and some heavy components. I recon i could get it to 20kgs.

I am looking at a couple of E fat bikes.
I as well would use the battery only when tired or when needed.
I want to live in the country away from the city lights.
An E fat bike would extend my range as far as errands are concerned.

When I get my shareroller sometime this spring or summer (hopefully) it will add a whopping 4.5 lbs inclusive of batteries to my sub 20 lb Bike Friday. Super easy on and off (10 seconds or less). Ideal in my mind for someone who only wants to use it on an infrequent basis, and prefers to ride "manually" 95% of the time. shareroller.com

When you get this and have had a chance to use it a bit, I for one would be quite interested in hearing about your experience.

Will definitely review it once used a bit.

Have you looked at the LIFT-MTB bolt-on kits? They use a MY1018 type brushed motor that can be mounted and unmounted easily to your existing light weight MTB if it has the chain guard 3-bolt mounts on the frame BB. Check their website out.

I just finished building a similar trail bike build using a 2013 Niner Jet 9 and an MY1018 motor. It is setup for hill climb assist ONLY. The rest of the time I ride it like a normal MTB;I pedal it. Here it is completed, but I haven't purchased the battery yet. I ride it like it is as a pedal bike now.

Thats a cool idea, using it for hills only. I just installed a kit on one of my bikes. I wouldn't ride it all the time, and don't always like the idea of a motor, but I think for commuting it will be great. It's jarring to go from power to manual because it feels so sluggish, it's the weight of the battery I think. I'm curious to get your feedback once you get on the trails with your build.

I have a Copenhagen wheel which I use 1-2 days a week for commuting. I swap it on and off one of my bikes. Total weight with the wheel is around 35 lbs which is reasonably light for an e-bike. I've run the battery down before and pedaled with no assist and it's not a big deal but I wouldn't want to do it all the time. The extra weight makes the bike sluggish. When I have it on I use it in the highest assist mode as I'm interested in shortening my commute. I don't really pedal any different than without the wheel but my commute times are shorter.

Fazua-based bikes are clocking in at 30lbs or less so that's promising. But the battery is not too big, but if you're saying you want to do a lot of the work, it's not a big deal.

Go with Fantic guys!!

The bike on the photo looks amazing!

Build it yourself is probably the lightest way to go – especially if you can tune it for what you need. Do you want a higher top speed, or the ability to climb hills, or both? If you can choose just one, you’ll be lighter than an OEM bike that has to do both.
My bike has (if I remember) about a 4.5lb battery and a 4.5lb motor. Both are very small and light for what they are. On a 19lb bike I’m around 29lbs all in – and it feels like a normal bike (even with the motor off). That and a bike that will do 25+ mph for 25 miles
Friction drive sounds like a good option (motor driving the tire directly). There are very few of these, so there must be some drawbacks. From what I have seen, the power ratings are misleading, and they are pretty noisy, and of course wear the tire rapidly. We are pretty interested to see how linberl’s set up works when he gets it going.

A build it yourself approach is great and is probably the way to go in order to achieve an end result that is a bike built from various components everyone of which is excellent in its own way, depending on available budget of course. However, for me as a newbie biker it looks like too advanced a project at this time.. I would love to build a bike from various great parts and make it "my own" in the future though..

My EasyMotion bike is 50 pounds. When I shopped a few years ago, that was the lightest front-suspension, cool-looking one I could find. Weight is the only limitation for me, and weight-savings is the only reason I would replace a bike I'm very happy with otherwise.