Combine two feeds to one

Hello, This may be obvious, but is there a way to add the data from a postprocess feed to an existing feed?
I have a calculated field that show my house consumption of the solar generated, but I only set this up a few days ago. I then used a postprocess to create the same data from the old feeds. I now have 2 feeds but need to combine them to one… Thanks

Hello @Tank you should be able to use the postprocessing to create the historic data and then attach the inputs with the relevant input processing to continue from there, does that make sense?

Trystan, thanks for the reply.
I have the set of historical data and the new data, but they are in different feeds. I would like to combine the feeds into just one, using the new data feed as the home for both sets of data.
Trying to combine the two sets using postprocess will not let me use an existing feed as the output.