2.5" 5400rpm HDDs are the most power efficient in my experience. They use around 1W when in normal use.
SSDs generally use power according to their actual utilization. The faster they are the higher the power consumption seems to be. SATA SSDs are generally slower and fall into the 1-3W bracket, NVMe SSDs are more like 5-10W, especially the PCIe 4.0 ones.
Don't quote me on these figures, I have not extensively tested them and they are very rough ball-park ones.