I boil in the kettle, and then pour it into a jug with a lid. It is then stored in the cupboard at room temp so I can then add the formula to make up the bottles without needing to heat it up.
With Dd I always boiled the water, allowed to cool in the kettle for 45 mins, then made the bottles up with formula and stored in the fridge. Only problem then is that you need to find somewhere to heat it if out and about.