I would not say this. Large companies that have many computers, lights, air-conditioning... are using Hive Electrical Technology which that reduces and will even shut-down coolling/heating/lighting systems in un or low utilized system areas and will automatically spin it back up when there is demand.
Many of the Green hosts also use Wind Energy; I know of five hosts in the greater Toronto Area have put in Wind Turbines and generate 300% of their needed power, the rest gets put back into the grid as electrical credits for them and green energy entering the grid. A number of hosts also have solar arrays that supplement their energy.
A common theme with Green hosts in our area, is they have aggressive recycling practices, they configure servers for lower electrical consumption, and they allow more than usual tele-commuting that lowers the carbon footprint.
You have to do you homework and understand what you do/don't consider to be Green, but there are companies that are doing this, not just because they want to be Green, but because Electricity is getting much more expensive and the corporate capital costs and green initiatives by our governments are encouraging host to move to cheaper Green electricity.
I do have a Green hosting company that I use and I don't really pay that much more, but even if it was more, I would be willing to pay it, help lower grid-dependency, and provide a marketing spin for my customers.