I want to implement the following in power query which involves looping inside rows.

Hi aakmpp,

your Power Query Code is interesting and you're on the right track with it, but there are a few small issues in your code, such as how you define the list of engines and how you loop through them.

I have tried to update (correct) the version of your Power Query code that should help to achieve your wishes:

let
    // Step 1: Load the "tbl" table
    Source = Excel.CurrentWorkbook(){[Name="G"]}[Content],
    //"G_Table" was commented out, so I removed it.
    #"Changed Type" = Table.TransformColumnTypes(Source, {{"Clock", type datetime}, {"E1", type number}, {"E2", type number}, {"E3", Int64.Type}, {"E4", type number}, {"E5", type number}, {"E6", type number}, {"E7", type number}, {"E8", type number}, {"E9", type number}, {"GrossGen", type number}, {"Active Energy Export MWh", type number}, {"Demand", type number}}),

    // Step 2: Define the list of engines explicitly
    Engines = List.Transform({1..9}, each Text.From(_)), // Create a list of engine column names: {"E1", "E2", ..., "E9"}

    // Step 3: Calculate Dependable Capacity (163/9)
    dc = 163 / 9,

    // Step 4: Calculate Remaining Demand
    RemainingDemand = #"Changed Type"[Demand],

    // Step 5: Loop through engines and allocate power
    AllocatePower = List.Generate(
        () => [i = 1, engineList = Engines],
        each [i] <= 9 and RemainingDemand > 0,
        each [
            i = [i] + 1,
            maxEngine = List.Max(engineList),
            allocatedPower = if maxEngine < RemainingDemand then maxEngine else dc,
            RemainingDemand = RemainingDemand - allocatedPower,
            engineList = List.RemoveFirstN(engineList, List.PositionOf(engineList, maxEngine))
        ],
        each [allocatedPower]
    ),

    // Combine the allocated power with the original table
    AllocatedTable = Table.AddColumn(#"Changed Type", "AllocatedPower", each List.First(AllocatePower))
in
    AllocatedTable

I created a list of engine column names using List.Transform so that you don't have to specify each engine manually and adjusted the table references to use "#Changed Type" where appropriate, as this is the step where you transformed your source data.