Of course we use HEATERS, what I mean is our 1,600kWh consumption this winter cost highier than a 1,600kWh during summer?
To schwildcat1977 : Yes the consumption is the same with that certain month last summer, since heatwave hits California so were always turning on the aircon. I lost the detailed charges of that month, only the total consumption so I can’t compare.

I work for an electric company. In all states electric companies are allowed to recover the cost of the fuel used to provide the power. If the power plants in your service area are natural gas feed, you’ll see a higher jump in the winter than in the summer. Its the result of supply and demand. If the plants use coal, you should see a pretty stable cost over the year. A number of states this year experienced a hugh jump in electrical cost because rate controls expired, you might be in one of those states.

If your electric company had several power plants down for maintence this winter, they may be buying power from other companies and that is always more expensive than producing it "yourself".

If you use the same number of kw in both months, the cost difference is in the cost of the fuel and the service fees to deliver the power to your house, and any rate increases in the last 6-8 months.