Blockchains are not for simple raw efficiency. The creator of Ethereum, Vitalik Buterin, explained how Ethereum is one million times less efficient than Amazon EC2 for computing, network and storage at this time.
Ethereum World Computer Compared to Amazon EC2 Cloud prices
Looking at Amazon EC2 (cloud) pricing. For medium scale computing the cost is 4 cents per hour.
Compare this to the cost of the Ethereum world computer.
Every Ethereum block comes every 14 seconds. Each block is processed in 200 milliseconds on a laptop.
The cost of filling an Ethereum block is about $13.40 for 200 milliseconds.
This is 1.4 million times more expensive than Amazon EC2.
Ethereum Network Size times safety factor makes network a million times more expensive
The Ethereum network size 15,000 nodes. There is a safety factor so the block interval is 14 seconds between blocks divided by the block verification time of 200 milliseconds. 14 seconds divided by 200 milliseconds is about 70 times. A node in the Ethereum network spends about 1/70th of its time actually doing computation. A fairly large safety factor is needed for reasons like keeping uncle rates down and having a buffer in case some attacker figures out some weighted denial service attack or other risks. The net overhead if you multiply the network size so everything gets processed 15,000 times multiplied by the safety factor one point zero five million.
Storage costs about $80 for 250 gigabytes harddrive. The Etherium world computer can fill one byte of contracts data which costs about 200 gas. Assuming ether is at $420 that gives you $84 million dollars for 250 gigabytes. 1.05 million factor overhead for storage as well.
Storage, network and computation all currently are about 1 million times more costly.
The Ethereum world computer is 1 million times less efficient than regular computers. Raw execution efficiency is not what blockchains give you.