That seems way high for an apartment, but it is a 6 week period and you keep temp a bit high. I have gas heat, water heater and stove in a SF home and used about 120 therms on the last bill. Heat usually 65 - 67, well insulated house. If you are ground level apt, your bill will also be higher since no heat rising from unit below. In summer, a/c would be less though.