Hi @dougrichardson. I expect the difference in size is just due to the compression applied by zarr. Are the uncompressed sizes the same if you read your zarr collections back in using xarray (e.g. see the size listed in the Array column and Bytes row of the DataArray html repr)?
It’s possibly also worth checking that all the zarr chunks were successfully written. With consolidate=True it’s possible to create a zarr collection that appears fine when you first open it lazily (from the consolidated metadata), but actually has data missing (e.g. if the writing of the chunks failed at some point, or if some chunks were deleted after the collection was created). For peace of mind, you could make sure that there are no NaNs in your zarr collections.