Or if you have a smart meter you can monitor total house usage with old appliance and new ... and also look at daily totals for things like freezers.
Looking at our daily 30 min graphs from octopus you can see things like dishwasher and washer dryer clearly on the graph (as well as oven at dinner time) where you dont see the fridge freezer as much.
Without a smart meter the above plug is a good guide, but smart metering is all about finding these things.