Pedal-powered head/tail lights I'm planning to get a pair of pedal-powered head &amp; tail lights to get my husband as a gift. 

He commutes ~11mi roundtrip every day to/from work. In summer, he rides a Cannondale touring bike. In winter he is riding a very old Mongoose he has had since he was a teenager (that one will eventually be replaced). 

We live in Buffalo, NY so he rides through all weather you can imagine and of course snow is the worst. He currently uses a couple if cheap lights that run on rechargeable AA batteries and he has to charge them every few days. 

So I want to get him a pair of lights that are powered by the pedals. I have looked online and I'm so confused by what I find. I don't know what are positive features, what is important, what to avoid ... I know it's important that they work well in the snow and other inclement weather as those are the most important times to be as visible as possible as to see as clearly around you while riding. 

Can you advise me please? Or least tell me what I should be looking for and why? And [added by editor] is replacing his battery powered lights the best way of doing the job?

What specs are important. What's a good price range. Any information will be helpful.
You can get lights that are powered by a dynamo (generator) in the front hub. Combined with bright LED front and rear lights you get excellent visibility (both seeing and being seen) and very little maintenance. The downside is that the equipment is not inexpensive – figure you'll need to spend at least $250 US for a front wheel, headlight and taillight.
My personal opinion is that dynamo light are a huge improvement over battery lights – because you don't have to worry about batteries running down or loosing capacity in cold weather. Not having to worry about batteries means that you can run the lights all the time too. The downsides of dynamo lights are that you take a small hit in terms of drag (the power it takes to run the lights) and that they are harder to remove. The latter means that your bike is a bit more of a target for thieves.
Dynamo lights are common in Europe and good ones will likely exceed German specs – from the bit of research that I did before buying my lights the German specs don't require a very bright headlight. I ride a lot on unlit roads and really appreciate a much brighter light, the brightness also helps keep the road visible when there are oncoming cars.
I do a fair bit of night riding and good lights completely transform the experience. For reference here's what I'm using:

IDC Stout front wheel – a good enough, solidly built, wheel using a Sanyo NH-H27 dynamo hub ($95 on e-bay). It was a gamble, so (2,500 km) far I'm well pleased. It flickers a bit more than the SON hub on our tandem, but for the price I've got nothing to complain about.

Busch &amp; Müller Lumotec IQ Premium Cyo T Senso Plus - a bright, wide LED headlight with a stand light (a capacitor in the light that provides power to keep the light going for several minutes when you're stopped) and a daytime light pattern that makes you visible to cars in the daylight – this really helps when you're in and out of shadows ($104 from Peter White Cycles). Busch &amp; Müller makes some less expensive lights but the Cyo is exceptional for range and beam width. The beam width is really nice when you're cornering in the dark. Range keeps you safe at speed. For anyone who rides on dark roads the Cyo is about the best light for the money. You can spend a bit less for a version without the daytime running light feature.
If you are more concerned with being seen than with seeing some of the lower powered lights might be a good choice. The Busch &amp; Müller Eyc (US $72 with the daytime running light, $66 without) puts out a very bright, but narrow beam (range is comparable to the Cyo, but you don't get to see as much on the sides). They also make a light called the Avy (US $42 without the daytime running light feature, US $56 with), which I haven't ridden with, but which sounds like it might be a good city light.

Busch &amp; Müller Toplight Line Brake Plus – a big, bright, rack mounted tail light with a &quot;brake light&quot; feature. The dynamo puts out AC and the tail light monitors the frequency of the AC, which is proportional to the speed of the bike, when the frequency drops the light glows brighter ($49 from Peter White Cycles, there is also a version for $34 without the brake light feature). The nice thing about this light is that the illuminated area is wide (3 or 4 inches) and seems to help drivers judge distance to your bike.


Peter White is the US importer for Busch &amp; Müller lights and is very knowledgeable about them – and they seem to have about the best prices on them. He also has photos comparing the beam patterns on his website.
One way to reduce cost a bit is with a [sidewall dynamo][6] (aka bottle generator). These cost about the same amount as a low-end hub generator (US $50 plus a mount which runs $10 to $15) and save the cost of building a wheel. The downside of the sidewall dynamos is that they require friction on the tire sidewall and may slip in icy conditions. Ideally the tire will be built with a reinforced sidewall for longevity. Some of the better models have a choice of drive wheels so that you can use a more aggressive one in the winter.