Is the standing charge included when querying cost?

Hello,

I'm using the API to retrieve the cost of consumed electricity for a given time period covering one or more days, with a 30 minute aggregation level. I can't work out whether the values returned include the standing charge, or just the cost of the electricity - it seems to vary, and I can't see a pattern for when it does. Is it supposed to include the standing charge, and if so is it in only one of the 30 minute periods (presumably 00:00 to 00:30 am)?

Thanks