The variable portion of the semi variable cost of electricity for a manufacturing plant is a conversion cost?

yes A cost that attaches to the physical units is termed a product cost. Product costs would include direct materials, direct manufacturing labor, and manufacturing overhead. Conversion cost is the cost involved in converting the direct materials into a finished product. It is composed of direct manufacturing labor and manufacturing overhead. Any cost that does not attach to the physical units would be termed a period cost and would be expensed as incurred. Therefore, a cost is either a period or a product cost. Electricity cost, whether variable or fixed, would be included in manufacturing overhead and classified as conversion costs, and therefore cannot be classified as a period cost.