The decision comes down to the following:

Remember… If you only pack camera batteries, then once you are out, you are out!

Let’s look at your options for cameras first, and then we will consider your other gear…

Most people who take their cameras on their adventures find that they get anywhere from 1-3 days per battery. Anyone sensible will be taking a spare, so with two or even three batteries, you will be able to power through 3-9 days (if nothing goes wrong!). So, for weekend trips, take a couple of batteries with you, and you will be fine.
dSLR camera are a lot more power hungry than the smaller point & shoots, and most serious photographers I talk to seem to want to budget 1 day per battery.A quick look at the current price of dSLR batteries will quickly make you look for alternatives for longer time frames. At anywhere from $80-$120 per battery, the 2 or 3 batteries you probably already have in your camera bag will suffice if you are looking at a trip of 7 days or less. But, you will need to control your shutterbug urges and stick to a power budget!
Because when your batteries are drained… you are done with the camera.

2. Solar Storage Battery = 3-4 dSLR batteries

Going for longer than 1 week?
Consider the advantages of using a solar storage battery to pack the extra power you will need. Cheaper than a complete solar kit, and cheaper than buying more camera batteries.
A solar storage battery is the equivalent of 3-4 camera batteries, but when you consider that the price tag is not much more than a single new Canon LP-E6 battery, the economics are obvious. Combined with your 2-3 back-up batteries, you now have the ability to go up to 2 weeks, or even 3 weeks for the smaller point-and-shoot cameras.
The advantages of using a solar storage battery…
1. Economy – saving money over buying more camera batteries.
2. Expandability – being able to add a solar panel later if you ever want to.
3. Versatility – works with any camera brand/model. There’s nothing worse than having a bag full of model x batteries @ $70each, only to decide to buy a new camera a year later.

What does a solar storage battery look like?
Here’s a current top seller… Voltaic V72
It’s about the size of an eReader (Kobo)
How would you get the power from the storage battery into your camera?
Use the solar storage battery to drive a universal battery charger via USB or 12V DC car charger for your particular camera model. The AC charger that came with your camera is not designed for this job.
examples: Ansmann Vario or Powerline Vario (USB) or DC LP-E6 charger.

3. Complete Solar Power Kit

This is for serious trekkers… this is the power system that generates power continuously. You will never run out of power as long as the sun comes up each day. The power varies with the strength of sunlight (latitude and weather), but we take all that into account when we recommend equipment for you.
So, if your trip is longer than 1-2 weeks, and/or you would rather not take chances with getting your power budget correct, using a complete solar kit is your best option.solar panel -> storage battery -> battery charger -> camera battery