Some would advocate a hard, literal line: if your entire operation is not solar-powered, then you're not "100% solar". Truly a noble and desirable goal, but with the current state of technology, a daunting and, frankly, intimidating one. We, on the other hand, believe that the best way to move toward that goal is to do what can be done, to focus on areas which, by themselves, can be made "100% solar".

In that spirit, we will consider to be "100% solar" any hosting provider which can credibly claim that the entire energy requirements of their hosting facilities are met completely by solar-generated electricity. And by "hosting facilities", we mean the network infrastructure (computers, routers, etc.) and not the lighting or HVAC. (Yes, those can be large consumers of energy, and we will positively note any sites which take meaningful measures to reduce or, ideally, solarize them. Remember, though, our focus is on the things we can do now.)

Additionally, that solar power has to be real. It may be generated onsite or purchased over the grid. It is not sufficient to buy so-called "carbon" or other credits that do not represent an actual replacement of fossil-fueled electricity with solar-generated power. It's perfectly acceptable to store excess solar electricity in the grid, but if a provider's system is grid-tied, then the total net usage for their hosting operations must be zero or negative. If the power is purchased from a distant provider and delivered across the grid, the remote supplier must put as much energy into the grid, on an average basis, as the provider uses, and that energy must not be double-sold. Schemes in which power is drawn from a local utility and somehow is magically made whole by some sort of "credit" or "tag" on a different grid are carbon offsets, and worthwhile, but are not direct solar power.

This said, we're going to have to rely on how forthcoming various providers are about their claims, what can reasonably be inferred from what they do reveal, and ultimately, their honesty. A decision to include a particular provider is based solely upon an assessment of how likely it is they they meet, or are trying to meet, the criteria laid out here, but is always subject to the limits of knowledge and human judgment, and does not represent an endorsement of that particular provider.