Hi palmo62,
Thank you for posting in Apple Support Communities. From our understanding, since switching to your new iPhone, the photos are taking up more storage then they did on the older device, is that correct? If so, are your settings the same? Do you optimize your photos on the new device with iCloud Photos? You can confirm by going to Settings > Photos. You'll want to confirm that the option that says " Optimize iPhone Storage" is selected.
Check out some more information on iPhone storage and ways to optimize it here: How to check the storage on your iPhone, iPad, and iPod touch.
Hope that helps!