Double boiler espresso machines are similar to heat exchange espresso machines. Both have the ability to pull your espresso shot and froth milk at the same time. The main difference is the boiler setup. Dual boiler espresso machines have 2 separate boilers, one for coffee and one for steam. This setup allows you to control the temperature of each boiler independently.
We at 1st-line Equipment, personally handpick the double boiler models we carry. We evaluate each model on a number of factors.