Watts are not the ranking
Monthly kilowatt-hours are watts multiplied by hours divided by a thousand, times about 30.4 days. That second factor is the one people leave out when they guess. A 3,000 W dryer running 45 minutes a day comes to roughly 68 kWh a month. A 45 W average refrigerator running continuously comes to roughly 33 kWh. A 1,500 W space heater running four hours a day comes to 182 kWh and beats both of them without being the largest appliance in the house.
Which is the point of listing everything side by side. The intuition that big appliances dominate the bill holds only when the big appliance also runs for a long time. Heating and cooling qualify, which is why they usually top the list. A microwave never does, no matter how many watts are on the label.
Getting the watts right for anything that cycles
Refrigerators, freezers, air conditioners and heat pumps do not draw their nameplate power continuously. The compressor runs, satisfies the thermostat, stops, and starts again. Entering the nameplate against 24 hours can overstate a refrigerator by a factor of four or more, and it is the single most common way a breakdown like this goes wrong.
Two ways to get the real number. The appliance's efficiency label states estimated annual energy use in kilowatt-hours; divide that by 8,760 hours and multiply by 1,000 to get average watts, then enter 24 hours. Or put a plug-in energy meter on it for a few days and read the kWh directly. The meter is better, because it captures your door-opening habits, your kitchen temperature and the condition of the door seal, none of which the label knows about.
The "everything else" line does real work
Lighting, chargers, the router and modem, the standby draw of everything with a clock or a remote, small kitchen appliances, the bathroom fan — individually too small to list and collectively substantial. Rather than guessing at it, derive it: take the kilowatt-hours from your bill, subtract what the listed appliances add up to, and enter the remainder. If that remainder comes out negative, one of your wattage figures is too high, and the cycling appliances are where to look first. If it comes out implausibly large, something is running that is not on your list.
That subtraction is the closest thing to a self-check this calculator has. A breakdown whose total does not match a real bill is a story about a house that does not exist.
What the savings column does and does not say
The last column of the ranking shows the bill with that appliance removed entirely. On a flat rate this is simply its kilowatt-hours times the rate, so the column is proportional to usage and tells you nothing extra. It earns its place on a tiered rate, where kilowatt-hours removed from the top of the month come off at the higher rate and the same cut is worth more.
What it never includes is the fixed charge. A customer or service charge is there whether the house uses one kilowatt-hour or two thousand, so it cannot be saved by using less, and any savings figure that quietly assumes it can is overstating the case. This is also why the percentage cut in usage and the percentage cut in the bill are different numbers, sometimes very different ones on a low-usage account.
Using the breakdown to decide something
The ranking is worth having because it points at where an hour of your attention is worth spending. If one line is 40 percent of the total, everything below it is a rounding error and chasing standby draw is a hobby rather than a saving. If the top three are close together, there is no single fix and the answer is probably about the envelope of the building rather than any appliance in it. Run the cut simulation on the top line at a reduction you would genuinely live with, not the one that makes the number look good, and see whether the annual figure is worth the change in how you live. Frequently it is not, and knowing that is also a result.
Questions people ask
Which appliance uses the most electricity in a typical home?
Whatever heats or cools, in almost every house that has electric heating or air conditioning: space heating, air conditioning and the water heater between them commonly account for the majority of residential electricity, with everything else dividing the remainder. Where heating and hot water run on gas, the ranking opens up and the top spot goes to air conditioning in summer and often to a dryer, a refrigerator or a well pump the rest of the year. The reason to run your own numbers rather than trust the general pattern is that the pattern is an average across climates, fuels and house sizes, and your house is one specific case.
Why does my refrigerator show so little compared to what the label says?
Because the label wattage is what the compressor draws while it is running, and it is not running most of the time. A modern refrigerator cycles perhaps a quarter to a third of the hours in a day, so its average draw over 24 hours is far below the nameplate. This calculator wants that average. Take the estimated annual kilowatt-hours from the yellow efficiency label, divide by 8,760 and multiply by 1,000 for average watts, and enter 24 hours. Nameplate against 24 hours is the error that makes refrigerators look like the biggest thing in the house when they rarely are.
Is standby power worth worrying about?
It is worth measuring once and then mostly forgetting. Devices left plugged in do draw power continuously, and across a whole house the total is real, but it is spread across dozens of items each contributing a fraction of a watt to a few watts. The ones worth switching off at a power strip are the ones drawing several watts around the clock — older set-top boxes, game consoles left in an instant-on mode, desktop peripherals. A phone charger with nothing attached is not worth the walk across the room. Put the whole-house standby figure in the "everything else" line and judge it against the total rather than in isolation.
Can I use this instead of a home energy audit?
No, and the difference is worth being clear about. This calculator divides electricity you already used among devices you already named, which tells you where the kilowatt-hours went. An audit tells you why the house needs them: where the envelope leaks, whether the insulation is where it should be, how the ducts perform, whether the heating equipment is sized and operating correctly. The two answer different questions and the audit answers the more expensive one. Use this to know whether the problem is a device or the building, then get the audit if the answer is the building.