Database

[{"_id":"5ede202d4195684e34492a6a","consumption":12,"charts":[{"date":{"year":2020,"month":6},"consumption":2},{"date":{"year":2020,"month":6},"consumption":1},{"date":{"year":2020,"month":6},"consumption":1},{"date":{"year":2021,"month":12},"consumption":1}]}]

Query

db.collection.aggregate([{$unwind:"$charts"},{$group:{_id:{_id:"$_id",month:"$charts.date.month",year:"$charts.date.year"},consumption:{$first:"$consumption"},total:{$sum:"$charts.consumption"},date:{$first:"$charts.date"}}},{$group:{_id:"$_id._id",consumption:{$first:"$consumption"},charts:{$push:{date:"$date",consumption:"$total"}}}}])

Result