I responded yesterday when I did not have much time to respond, elaborating more here.

I built up my own touring bikes from parts. Thus, for me a dynohub did not cost much, the only cost was the hub, minus the cost of the non-dynohub that I otherwise would have bought. I usually build my own wheels. But for most people, buying a dynohub would cost much more, the dynohub, the rim, the spokes and nipples, and maybe a wheel build fee.

Dynohub puts out alternating current with very variable voltage depending on speed. You need a way to convert AC power to 5 volt DC power if you are using USB devices or powerbanks that are charged by USB. I initially used a Sinewave Revolution, a good charger with outstanding waterproofness. But in summer 2022 I bought a Cycle2Charge USB charger that puts out roughly 50 percent more electric power than the Sinewave.

I think that Happy Feet that used to post on this forum and Gauvins that still occasionally does instead use solar power, I think that they have both operated self sustaind with just solar. I think Gauvins used to use a dynohub, but switched to solar.

But a big part of this is being very frugal with your electricity, only use what you need, when you need it. Phones in daytime will need a lot of backlight to be readable, and a lot of backlight is a lot of power. GPS units on the other hand do not need any backlight at all in daytime. With my Garmin 64 I often need a bit of backlight in early morning or evening when it is still quite light out but the sun is low, but during daytime I keep the backlight off. I run my GPS so that the screen is always on (so I do not have to keep taking my hand off the bars to push a button to wake up the screen), but with the backlight off, it consumes almost no additional power to keep the screen on.

I assume that I am averaging about 2 watts of power generation when riding on fairly flat ground, more hilly terrain average maybe 1 watt, and in very hilly terrain I get much less. When I first installed the Cycle2Charge, I did some tests, these are the results:
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• 6.5 mph to get any power at all, below 6.5 it did not turn on.
• 9 mph was about 0.6 amps, or 2.9 watts.
• 11 mph was about 0.8 amps, or 3.9 watts.
• 15 mph was about 1.0 amps, or 4.8 watts.
• 22 mph (shallow downhill, briefly) about 1.25 amps, or 6.1 watts.

When you look at those numbers, you can assume you will get much more than my estimates, but on a tour my speed is not that high (I am 71). But if I was in Florida and never had to pedal more slowly up a hill, I would probably produce much more. I was self sufficient on my 2017 Florida bike tour with the Sinewave Revolution for two weeks.

Thus, on a good day, I might produce 12 to 15 watt hours of power. But I probably consumed one third of that by running my GPS. And I am using a 44 watt hour powerbank, so at best I am only producing maybe one quarter of the power that my powerbank is capable of holding.

You can buy some really good powerbanks that hold 72 watt hours (I have two of that size, but do not bring them on bike tours) for very little money.

I really think that if your tour is a week long, or if you plan to sleep indoors at least once a week, you are better off just buying some good powerbanks, not trying to generate your own power. Before I started using a dynohub, I always looked for seating in restaurants near outlets to charge batteries. With the high output USB-C chargers, you could get a lot of power into a powerbank, simply by getting lucky by getting a good place to sit in a restaurant to charge up a powerbank.

I would suggest not buying any powerbanks that are 100 or more watt hour capacity, flying restrictions could prevent you from taking that size powerbank on a plane.

But, if you are a power hog, bring your laptop computer with you, want your phone on all day every day, use a rechargeable tall light with humungous Lumens, you might want to just credit card tour so you can charge up everything every night.

A friend of mine bought a really bright taillight for touring, at full brightness on flash, it lasted less than five hours when brand new before the battery was dead. Oops.

I have a meter that can tell me how much power I am getting out of my dynohub, as long as the sun does not shine on the LED display which is not very bright. In the photo, 0.44 amps, I suspect at about 4.9 volts, thus a hair over 2 watts.