Calculating Mean Time Between Failure

let
  Source = Table.FromRows(
    Json.Document(
      Binary.Decompress(
        Binary.FromText(
          "fc+7CoQwEAXQXwmpFe9MHI3TbSM2wvZiYb+l/r/IhCDq2h/uY5r8sPzWsqfGFx5UQSoGBxc0dAq4z+j8XPxTxFrzwb7jgyKYYhWxrDNqEyJDtYLuKLqk2lwIWKHt6pftgEEuDkr85mJyKjHfnHc=",
          BinaryEncoding.Base64
        ),
        Compression.Deflate
      )
    ),
    let
      _t = ((type nullable text) meta [Serialized.Text = true])
    in
      type table [Equipment = _t, BreakDownDate = _t]
  ),
  #"Changed Type" = Table.TransformColumnTypes(
    Source,
    {{"Equipment", type text}, {"BreakDownDate", type datetime}}
  ),
  #"Grouped Rows" = Table.Group(
    #"Changed Type",
    {"Equipment"},
    {
      {
        "Rows",
        each Table.AddIndexColumn(_, "Index", 0, 1, Int64.Type),
        type table [
          Equipment = nullable text,
          BreakDownDate = nullable datetime,
          Index = Int64.Type
        ]
      }
    }
  ),
  #"Added Custom1" = Table.AddColumn(
    #"Grouped Rows",
    "NewRows",
    (k) =>
      Table.AddColumn(
        k[Rows],
        "MTBF",
        each if [Index] = 0 then null else [BreakDownDate] - k[Rows]{[Index] - 1}[BreakDownDate],
        type duration
      )
  ),
  #"Expanded NewRows" = Table.ExpandTableColumn(
    #"Added Custom1",
    "NewRows",
    {"BreakDownDate", "MTBF"},
    {"BreakDownDate", "MTBF"}
  ),
  #"Removed Other Columns" = Table.SelectColumns(
    #"Expanded NewRows",
    {"Equipment", "BreakDownDate", "MTBF"}
  ),
  #"Changed Type1" = Table.TransformColumnTypes(
    #"Removed Other Columns",
    {{"BreakDownDate", type datetime}, {"MTBF", type duration}}
  )
in
  #"Changed Type1"

How to use this code: Create a new Blank Query. Click on "Advanced Editor". Replace the code in the window with the code provided here. Click "Done". Once you examined the code, replace the Source step with your own source.