I use a duvet to minimize how much I need to wash the comforter. However most polyester and some down (I have one made by Pacific Coast - were sold at Costco and on QVC as Northern Nights) comforters can be washed in a washing machine. I wash and dry mine in my large capacity washer and dryer. I also add the washer balls to keep it from shifting.
Mine is also used only in winter and stored in the summer.
Does yours have a label with care instructions, since some do need to be dry cleaned.