Look for cheap or free heat, such as wasted heat. Some composters have convenient air intakes that can be connected to a warm air source, such as:

• An insulating fire proof box with an incandescent light bulb in it
• A heat exchanger connected to the exhaust system of a generator or the flue from a gas hot water heater
• The lint-filtered exhaust from your clothes dryer
• Hot discharge air from your air conditioner or dehumidifier
• Solar heat from a solar collector, window, or a greenhouse
• In the summer, hot air pumped from your attic via a fan-powered duct
• A connection from an existing space heating system
• Bread box solar heater

More sophisticated systems like heat pumps, while elegant from an engineering point of view, are often cost prohibitive for use with a composter alone.