[damien_ls]

Generally speaking, a VPS can potentially provide a "greener" hosting environment than a dedicated server - the whole virtualisation trend is build from a foundation of getting better resource utilisation from the high powered servers now available as "commodity hardware".

To put this in context, our VPS nodes use around 2-3x the power consumption of one of our dedicated server customers, yet there can be 10+ VPS's on one of these nodes running some quite intensive sites.

It's also worth mentioning that power supplies run more efficiently under load, and therefore buying an overpowered dedicated server for your own use and having that PSU idling a lot is definitely not the greenest solution! A VPS on the other hand is generally quite scalable (i.e. meaning that you don't have to buy something much larger than your current needs, as you can easily scale to a larger version at a moment's notice when required), and your provider will of course manage their nodes (physical servers running VPS's) such that they're not under-utilised.

Of course the balancing act is ensuring that they're not over-utilised, which is why you should only buy VPS services from a provider with plenty of experience who knows what they're doing etc. - it's easy to degrade service by overloading nodes, but there are enough high quality providers around who know how to manage their servers properly to avoid that happening!

Disclaimer: We sell VPS and dedicated servers. Whilst I'm clearly an advocate for VPS's, I do of course recognise that they don't fit every scenario: just curious if the OP has fully explored this option to establish its viability for their project?