A lot of electricity is used on other forms of security as well, such as SSL or password encryption. Although SSL uses up less resources, it is used by far more servers, which I suspect would exceed the amount of processing power of the Bitcoin network.
Individually SSL takes less CPU time, but in aggregate there is an awful lot of SSL traffic in comparison to Bitcoin. I suspect that overall the cumulative amount of CPU time spent on more conventional cryptographic security far exceeds the CPU time spent on Bitcoin's blockchain.
