Dynamo lighting is green energy. A generator in or on the wheel siphons off a little pedalling energy to power your bike lamps. It's the predominant system in countries where transport cycling is popular, such as Germany and the Netherlands, because it's so convenient. Your lights are bolted to your bike and are always ready to shine; there's no recharging routine to remember or disposable batteries to buy, and no faffing with fixture or removal each ride.

Dynamo lighting is green energy. A generator in or on the wheel siphons off a little pedalling energy to power your bike lamps. It's the predominant system in countries where transport cycling is popular, such as Germany and the Netherlands, because it's so convenient. Your lights are bolted to your bike and are always ready to shine; there's no recharging routine to remember or disposable batteries to buy, and no faffing with fixture or removal each ride.

The only real downside is a small amount of drag. And it is small. At typical commuting speeds, and depending on its efficiency, a dynamo might require 5-15 Watts of your energy. That will slow you down by less than 1mph, or less than 0.5mph for more efficient systems. That's assuming you don't just pedal a bit harder.

There are two popular types of dynamo: ones shaped like a bottle that press a little roller agains the sidewall of the tyre; and ones where the generator is built into the hub. There's also the Reelight system (see below), which works by magnetic induction.

Bottle or sidewall dyanmos are the cheapest. They used to be the most common, although they are being overtaken by hub dynamos these days. They work better if the tyre has a file-pattern dynamo track on the sidewall. Some slip badly in the rain, which means you lose power – and light! The better ones (Axa, Basta, Busch und Müller, Nordlicht) cope well enough with most conditions short of snow, sleet or mud. You can improve performance and reliability by taking care to orient the roller on the tyre just right, and by making sure the roller is pressing on the tyre properly, not just skimming it.

Hub dynamos are, as a rule, more efficient and reliable than bottle dynamos. The drag is lower and they don’t slip. They tend to cost more, however, and you can't just bolt them onto your bike: you need a new wheel, with the new hub at its centre. Your local bike shop can build this for you.

As well as the generator, you'll need lamps. Almost all dynamos are 6 Volt systems with a 3 Watt output, powering a 2.4 Watt front lamp and 0.6 Watt rear. If you run a battery-powered LED rear light, you can fit a 3 Watt bulb up front for extra brightness. Lacking raw power, a lot of work has gone into designing dynamo lamps to make best use of the power they have, and even a 2.4W front lamp will provide enough light for unlit lanes.

Many dynamo lamps incorporate a reflector and some have a stand-light, which comes on when you stop. This is a secondary LED in the lamp, or just the main LED if it’s an LED lamp. The dynamo charges a capacitor, which powers the LED. It’s seldom bright enough to see by but it’s enough to get you seen.

The suggestions here are not exhaustive. They are intended to give an idea of the range available.

Generators

Lamps