 8.7 percent on average. In a statement by Duke Energy South Carolina, they say it marks the first base rate increase requested by the company since 2018. Locally, the rate hike will affect about 39,000 customers each in York and Lancaster County. For Chester, it'll be nearly 15,000 to be impacted. On average, the increase could be about $151 for residential customers annually. The new rates change on August 1st.