A year earlier, area consumers paid 24.7 percent more per therm for natural gas compared to the nation. In the Los Angeles area over the past five years, the per therm cost for natural gas in August has varied between 11.7 and 36.8 percent above the U.S. average.or electricity, average prices per kilowatt-hour (kWh) and per 500 kWh are published. For utility (piped) gas, average prices per therm, per 40 therms, and per 100 therms are published.