All of the espresso machines we tested only included a single boiler for heating. This means that there's only one mechanism for heating both the water for brewing and the steamer wand. Because of this, it'll take the steamer wand a while to heat up after pulling the espresso shot, since the steamer wand operates at a much higher temperature than the brewing temperature of around 195°F. It is possible to buy a home machine with a double boiler (Breville makes one) but this raises the price significantly (we didn't test the Breville because it's over $1,000), and the minor wait time wasn't a major concern for us. We figured it wouldn't be for home brewers either.
An electric drip coffee maker can also be referred to as a dripolator. It normally works by admitting water from a cold water reservoir into a flexible hose in the base of the reservoir leading directly to a thin metal tube or heating chamber (usually, of aluminum), where a heating element surrounding the metal tube heats the water. The heated water moves through the machine using the thermosiphon principle. Thermally-induced pressure and the siphoning effect move the heated water through an insulated rubber or vinyl riser hose, into a spray head, and onto the ground coffee, which is contained in a brew basket mounted below the spray head. The coffee passes through a filter and drips down into the carafe. A one-way valve in the tubing prevents water from siphoning back into the reservoir. A thermostat attached to the heating element turns off the heating element as needed to prevent overheating the water in the metal tube (overheating would produce only steam in the supply hose), then turns back on when the water cools below a certain threshold. For a standard 10-12 cup drip coffeemaker, using a more powerful thermostatically-controlled heating element (in terms of wattage produced), can heat increased amounts of water more quickly using larger heating chambers, generally producing higher average water temperatures at the spray head over the entire brewing cycle. This process can be further improved by changing the aluminum construction of most heating chambers to a metal with superior heat transfer qualities, such as copper.