They sell pediatric or "nursery" water here in the States that's already sterilized, so I'd fill up my bottles with the correct amount of water and bring them into the nursery with me (I sleep in the nursery with the baby's crib) along with the carton of powder formula. That was the easiest way for me to mix a bottle in the dark and serve it immediately at room temperature. Unfortunately, our pediatrician switched her formula to Similac Alimentum (hypoallergenic) and although there is a powder version, my daughter will only drink the ready to feed liquid. Since it has to be refrigerated, I have to warm it up for her. She was taking it cold, straight out of the fridge, but went on a food strike and now will only eat if it's warm, almost hot. The good part about the RTF is that there is no Cronobacter worry; the liquid is sterilized.