One watt is a unit of power. It does not directly relate to the amount of electrical energy, or degrees, consumed in a year. To determine the annual energy consumption in degrees, you would need to know the power consumption in watts and the number of hours used per year, and then multiply those two values together to find the total energy consumption in watt-hours. After that, you could convert watt-hours to degree-hours, assuming a temperature change per unit of energy and an efficient electrical-to-thermal conversion.
On erage, 1 degree Celsius of temperature change requires about 4.19 kJ (kilojoules) of energy. Considering a 100% efficient DC-to-heat conversion, 1 watt-hour (Wh) of energy corresponds to approximately 3.412 degrees Celsius-hours (°C.h), or 6.11 degrees Fahrenheit-hours (°F.h).
Thus, the formula to calculate the annual energy consumption in degrees would look like this:
Degrees consumed in a year = Power consumption (W) * Hours used per year * Temperature change factor (K / Wh)
Be sure to consider the insulation efficiency and temperature rise for precise results.