In addition to all-electric melting, glass production can be enhanced by electric "boosting." This technique uses electricity in conjunction with gas, increasing the melting rate above that possible with fuel combustion alone. The amount of energy used per ton of glass melted is thereby reduced, even when all the fuel used to generate and deliver electricity is considered. Some factories have increased their output 60 percent by electric boosting alone. Although overall fuel use may be less with electric boosting, the energy cost per ton is dependent upon the cost of power used.
About 22 kW (or 22 kWh per hour) produces an additional ton of glass per day by electric boosting. Therefore 220 kW would increase the output of a fuel-fired furnace by 10 tons of glass per day. Large boosters with power requirements of up to 4,000 kW have been used to almost double the output of some fuel-fired glass melting furnaces.
The average electric rating of all-electric direct resistance glass melters is about 700 kW. Small furnaces producing one ton per day require 75 kW for melting and 30 kW for holding. A large furnace (120 tons per day) can require 6,000 kW electric rating.
