That is a good question, and one that is difficult to answer without knowing what kind of heater you use. For example, a slow-burning stove would generate more heat than a conventional fireplace. The quality of the wood you use may also be a factor.
Regardless, the average net heat rate for a small cord of dry hard firewood (4 ft. x 8 ft. x 16 in.) is estimated at about 2,700 kWh. As burning equipment usually performs at between 40% and 70% efficiency, the 1,500 kW you mention are definitely plausible. The equivalent in electricity consumption is $0.0860/kWh, or $129, plus tax.
However, these are just rough calculations; a heating equipment specialist would be better equipped to advise you on this matter.