Inverter sizing for coffee machines, microwaves and induction

The short answers: a pod coffee machine (900 to 1200W) wants a 1700W or larger pure sine inverter; an espresso machine (1200 to 1500W) wants 2200W to cover the surge from its pump and heater; a microwave with a nominal 900W power rating can draw 1600 to 2100W during surging from the socket and wants 2200W at minimum; a microwave with a nominal 1300W power rating can draw 2300 to 3000W during surging from the socket and wants 3400W at minimum; a jug wants 2100W+, so again a 3400W model will be the minimum; and a single 2000W induction ring wants about 4000W. Every one of these is a pure sine wave job.

Coffee first, because it's the question we're asked most. Pod and capsule machines heat a small thermoblock, a big but brief draw, and both pod and espresso machines surge above their label rating on start-up from the onboard pump. A 1700W pure sine inverter handles most pod machines; espresso machines with a boiler pull 1200 to 1500W and hold it longer, and their pump and heater cycling is exactly the load that will trip a marginal inverter, so 2200W is the right number.

Microwaves lie on the label. The wattage on the front can be the cooking power out, not the electrical power in: a "900W" microwave can surge to 1600 to 2100W at the socket. Read the label on the back, then size for at least two and a half times that figure, and pure sine without exception; modified sine under-powers a microwave and stresses the magnetron. A jug or kettle is the other one: it's one big linear resistive hit, ~2100W and up.

Induction is the largest common load, the sheer power rating size plus massive amounts of surging. A single portable ring can pull its full 1800 to 2000W with fast switching that's a hard load on an inverter, so around 4000W of inverter is the realistic minimum.

The pattern behind all these numbers: heat is expensive from a battery. Anything whose job is getting something hot, coffee, microwave, induction, jug, toaster, hair dryer, draws a kilowatt or more, and as well as the inverter the battery bank and the cabling are under significant demand. Our rule at the counter: heating appliances are fine as minutes-long events on a well-sized system, and wrong as an everyday habit on 12V. If the plan involves daily induction cooking off-grid, that's a whole-system design, preferably 48V, a serious bank and serious solar, not just an inverter, and we're happy to do it. Contact us with the appliance list and we'll design it.

The sizing guide has the method behind these numbers, and the campervan page covers the whole van system.