To bake sweet potato:
Wrap in aluminum foil and bake in 350 F degree / 176 degree C oven until soft (about 1 hour). Make sure it is well wrapped so that the potato doesn't leak as it starts to soften.
When soft, remove from oven and let cool in fridge until you are ready to use it. It will keep in the fridge for several days.
For energy efficiency, prepare the sweet potato in advance while you are baking other dishes in your oven. Don't worry if the temperature is higher or lower than 350 degrees F / 176 degrees C - just bake the sweet potato until it is soft.