Bitcoin : Energy Wasteful
343 megawatts would be enough to power 285,833 US homes per secondWhich becomes:
20,580 Megawatts per minute 1,234.800 Gigawatts per hour 29,635.200 Gigawatts per Day10,816.848000 Terawatts per Year
https://www.thebalance.com/how-much-power-does-the-bitcoin-network-use-391280
At the time of writing, the computers on the bitcoin network were doing 342,934,450 Gigahashes per second.
There are lots of different bitcoin mining computers out there, but in recent months, companies have focused on ASIC miners, which use less energy to conduct their calculations. Mining companies that run lots of ASIC miners as businesses have told me that they use one watt of power for every Gigahash per second of computing that they do when mining for bitcoins.
At this rate, the bitcoin network runs at 342934450 watts, which equates to around 343 megawatts. Calculations based on EIA data reveal that the average US household consumes about 1.2 kilowatts of power, meaning that 343 megawatts would be enough to power 285,833 US homes at the time of writing (May 2015).
Proof of Stake is Harder to Calculate , Because it is extremely more energy efficient
Because it can be run as a Minimized app on a PC, while the PC is performing other Functions
Example:
A Web or File Server is running 24x7 anyway, running a minimized app in addition would not show any noticeable increase in electricity required
So for a Large Portion of Users there will be a
ZERO increase in Energy Usage.
But for your example , Let's say the PC is dedicated to Proof of Stake only.
Average PC runs at 100 watts.
PoS network with active nodes
1 node in 24 hours uses 2.4KWh
In 1 year 1 node uses 876 KWh
Minimum nodes for a PoS network to run
3 nodes would use 2,628 KWh per year
Larger # of Nodes
12 nodes would use 10,512 KWh per year
100 nodes would use 87,600 KWh per year
1000 nodes would use 876,000 KWh per year
10000 nodes would use 8,760
MWh per year
* If the PCs were being used for other tasks or only used a few hours a day, then the energy draw would be significantly less. 
But in a Quick Yearly Compare
10,000 PoS nodes use less than
9 MWh per year Verses BTC using Over
10,000 TeraWatts Or put another way ,
the BTC network uses more electricity in 1 Minute 20,580 Megawatts per minute
than a Proof of Stake Network would use All Year 8,760 Megawatts per Year
FYI:
BTC Energy drain calculations above only uses the ASICS, but they also have ~6000 PCs that run as Full Nodes to store & transmit the blockchain, and their electricity usage would be comparable to a PoS node. We also don't know if the cooling systems were included in the BTC calculations or not.
When , not if a Proof of Stake takes BTC place as head of the Coin world, the energy savings will be tremendous, because as BTC keeps drawing more and more power they are raising the electricity prices across the world to compensate for the increased infrastructure to support their wastefulness.
Even if you are not a miner, they are driving your electricity prices up.
