When the total network hashing power get higher you get less BTC for your shares.
So if the BTC stays at the same price but the network speed gets 10 times as fast, and normally you need 10% of your BTC to pay the bills for the electricity, you now need all of your BTC to pay for electricity.
FPGA's are about 10 times as cheap in electricity consuming so they will rise from 1% of your BTC to 10% of your BTC.