Your numbers are way off.
Energy consumption is massively impacted by the size of the semiconductor die, e.g. 110 nm vs. 50 nm vs. 20 nm. Currently, most ASIC rigs are using 110+ nm chips, but the currently available semiconductor techology available to OEMs is in the 2x-nm class. The 1x-nm class isn't far behind now.
Have a read around here:
http://www.samsung.com/global/business/semiconductor/minisite/Greenmemory/That will give you an idea about how die size affect energy consumption.
With ever smaller classes of chips, energy consumption will decrease. So, any prediction of future energy consumption must take into account the energy efficiency of semiconductor technologies available in the future.
For example, would you calculate it in cords of wood or tonnes of coal for a steam engine to produce your electricity? Of course not, because that technology is pretty much obsolete now (outside of a few specialty cases).
The power efficiency of the mining equipment is not as relevant as you think. Mining is a nearly perfectly competitive market. Miners will increase the amount of mining (and therefore the amount of energy consumed) until their profits are reduced to some tolerable level (below that they stop mining).
The relevant numbers are:
1. The number of bitcoins mined (from the reward and the transaction fee) and their value.
2. The cost of the equipment.
3. The cost of the power.
4. The operating margin of the miners.
The cost of mining will rise to the value of the mined bitcoins minus the margin. The cost of mining is the cost of the equipment plus the cost of the energy. So, the amount of energy spent on mining is the value of the mined bitcoins minus the margin and minus the cost of the equipment.
Also, as the cost of the equipment drops (assuming that it does), energy cost will become the dominant limit, regardless of the power efficiency of the equipment.