The provision of reserve generation is an essential part of maintaining a reliable electricity system and has become an increasingly difficult task with the growing contribution from variable energy sources. Ensuring the cost of balancing supply and demand is minimized is an important aspect which requires an understanding of how generator costs vary depending on their operation. This paper considers the cost of part loading different generator types, providing a cost breakdown and description of the LCOE method of analyzing generator costs. This delivers cost-loading level curves for the generator types with the largest contribution to the UK generation portfolio. The holding payment for provision of frequency response is separated by generator type and compared with the calculated part loading costs.