The company provides both natural gas and electrical services to millions of customers. If you're one of those customers you can estimate your PG&E; costs each month by finding out the cost for each utility and multiplying that number by the total amount you've been using.

Examine your PG&E bill to find the total amount of electricity you use -- measured in kilowatt hours, or kWh -- and the total amount of natural gas you use -- measured in therms. Your bill has your usage statistics listed in one-month increments.

Find out what "tier" you are in for electricity. PG&E charges different rates for kilowatt hours of electricity based on your usage. For example, if your bill indicates that you use 101 percent to 130 percent of your "baseline" allowance, you are charged 14 cents per kilowatt hour and are in "Tier 2". If you do not exceed your baseline, you are charged 12 cents per kilowatt hour and are in the "Baseline" tier.

Multiply the total number of kilowatt hours of electricity listed on your bill by the charge for your tier. For example, if you are in "Tier 2" you are charged 14 cents per kilowatt hour. The number you get is the cost of your electrical charges for one month. For example, if your bill says you used 1,000 kilowatt hours of electricity, 1000 x 0.14 = $140.

Multiply the total number of therms of natural gas listed on your bill by $1. PG&E charges an average of $1 per therm of natural gas. The number you get is the cost of your natural gas charges for one month. For example, if your bill says you used 250 therms of natural gas, 250 x 1 = $250.