Ecomodded, where were the bottles stored while the fridge was being tested without them? Did you start the test with bottles immediately after the test without? Or did you allow 1-2 days for the bottles to reach fridge temperature before resuming testing? Also, was the kitchen's temperature the same during all tests? No open windows or sunlight?
Displacing volume in the fridge reduces the amount of cold air that escapes when the door is open, so the more often the door is opened during both tests, the larger the difference in energy consumption. If you hardly open the fridge door (which I was able to do when living alone
), then the bottles only increase the compressor on and off cycles. This is also good for the fridge, but more in the long term.