Power Sizing Guides

The sizing calculator gives you an answer in a few seconds. These guides explain the reasoning behind it, because a number you understand is a number you can argue with, and sometimes you should.

They exist for three reasons. First, the arithmetic has genuine traps in it, and almost every oversized generator and every undersized battery comes from the same handful of mistakes: adding every start-up surge together instead of one, treating a nameplate rating as a continuous draw, and forgetting that a fridge compressor is off for two thirds of every hour. Those mistakes are easy to explain and hard to spot on your own.

Second, the equipment itself behaves in ways the labels do not describe. An espresso machine's plate says 1,800 watts, and it draws that for perhaps a fifth of a service. A blender says 1,500 and demands 4,500 for the instant it starts, which is why it trips inverters that carry far heavier loads all day. A fryer never surges at all, because it has no motor, but it will sit at full draw for as long as you keep dropping frozen food into it. None of that fits in a single column of a wattage chart.

Third, the right answer is often not a bigger machine. It is a soft starter on an air conditioner, or staggering the grinder and the steam cycle, or moving the cooking to propane and leaving the electrics to refrigeration and lights. Those options save real money, and they only become obvious once you can see which item in your list is actually setting the size.

Every figure quoted below is computed at build time from the same equipment data the calculator uses, so the guides and the tool cannot drift apart.

Where to start

If you are new to this, read starting watts versus running watts first. It is the concept everything else depends on, and it takes about five minutes.

After that, follow your situation. Backing up a house: how many watts a refrigerator uses, then what size generator to run a house. Running a truck or a cart: what an espresso machine really draws, then food truck generator sizing. Camping or touring: what size generator for RV air conditioning, then sizing power for your rig.

Still deciding what to buy at all? Generator or battery power station compares the two on cost per watt, cost per stored kilowatt-hour, refuel time and where you are allowed to run them. And when you just need a number for one appliance, the appliance wattage chart lists every item in the catalogue with its running, starting and average draw.