Electricity Bill Split Calculator

Three ways roommates split a power bill

There is no single right answer, but there are three methods, and each one is fair in a different way.

• Even split. Divide the bill by the number of people. Simple, fast, and fair when the rooms and habits are similar. It stops being fair the moment one roommate runs a window air conditioner all summer and another is never home.
• Weighted split. Give each room a weight based on what it draws. A room with a window AC or a space heater counts as 1.5 shares, a normal room as 1. People accept this because the reason is visible.
• Metered split. Measure the heavy loads with a smart plug or a submeter, subtract those kilowatt-hours from the total, and split what is left evenly. This is the most accurate method and the one that ends arguments fastest.

Pick the lightest method the household will follow. A perfect metered split that nobody bothers to maintain is worse than an even split everyone trusts.

Whatever method you choose, start from a real number. The EIA Electric Power Monthly reported a national average residential rate of about 18.31 cents per kilowatt-hour in July 2026, and rates differ by more than double between states.

Worked example: a $180 bill, four roommates, one AC

Defaults: a $180 monthly bill, 4 roommates, 1 room with a window AC counted at 1.5 times a normal room, and nothing taken out first.

• Amount left to split: $180.00
• Total shares: 3 normal rooms at 1 share plus 1 room at 1.5 shares = 4.5 shares
• Cost of one share: $180.00 divided by 4.5 = $40.00
• Each standard roommate pays: $40.00
• The AC roommate pays: $60.00
• Even split for comparison: $45.00 each

Check the arithmetic: 3 x $40.00 plus $60.00 is $180.00, so the bill is covered. The AC roommate pays $15 more than an even split would charge, and each of the other three pays $5 less. That is the whole point of weighting, and it is small enough that nobody feels punished.

Worked example: a $95 bill with a charge pulled out first

Sometimes part of the bill belongs to one person. A late fee, a deposit installment, or a piece of equipment only one roommate uses should come out before the split.

• Total bill: $95.00
• Fixed charge pulled out first: $15.00, owed by one roommate
• Amount left to split: $80.00
• Three roommates, one with a space heater at 1.5 shares: 2 plus 1.5 = 3.5 shares
• Cost of one share: $80.00 divided by 3.5 = $22.86
• Each standard roommate pays: $22.86
• The space heater roommate pays $34.29 plus the $15.00 fixed charge, or $49.29
• Check: $22.86 + $22.86 + $34.29 + $15.00 = $95.01 using the rounded figures, and $95.00 exactly before rounding, which is what the calculator reports

An even split of $95.00 across three people would be $31.67 each, which overcharges the two light users and undercharges the one running a heater every night.

What the heavy appliances add to a bill

Weighting a room at 1.5 shares is a shortcut. Here is what the actual appliances cost at the national average of 18.31 cents per kilowatt-hour:

Read that table against the weighting. A single window AC adds about $44 a month, which on a $180 bill shared by four people is 24% of the total. Weighting that room at 1.5 shares only shifts $15. If the AC runs all summer, a 2 share weight, or an actual measurement, is closer to fair. The Department of Energy savings hub has guidance on cutting these loads before you argue about who pays for them.

Reading the meter instead of guessing

Guessing at weights works until someone disputes them. A $20 smart plug solves it. Plug the window AC, the space heater, or the gaming rig into it for a month and read the kilowatt-hours off the app. Multiply by your rate and you have the exact number to subtract from the shared total before the even split.

For a whole room, a plug-in submeter costs $30 to $60 and measures everything on that circuit. Landlords in some states allow a tenant to request a submeter. If the building has one meter and four units, measuring the one or two heavy loads is usually enough, because everything else, lights, laptops, a television, is small and roughly equal.

Writing a split rule that survives a roommate change

The method matters less than writing it down. A one-page agreement that says how the bill is split, who pays the utility, and what happens when someone leaves prevents the arguments that end friendships.

• Name the method: even, weighted, or metered, and the weight each room carries.
• Name the due date, a few days before the utility due date, so the payer is never fronting the money.
• Say what happens to a deposit or a late fee, and who owes it.
• Say what happens when a room sits empty for a month, and whether the remaining roommates absorb that share.
• Say how much notice a roommate gives before moving out.

A new roommate signs the same page. When the rule is on paper, the split stops being a negotiation every month.

The disputes that come up most

Four arguments cover almost every shared power bill.

• A guest who is there every night. The common answer is that a guest staying more than a set number of nights a week counts as a roommate share, and it should be written down in advance.
• A room that sits empty. Most agreements split the bill among current roommates, which means the others cover the empty share. Decide this before it happens.
• The thermostat. Heating and cooling are usually the largest lines on the bill. Set a range everyone agrees to, and let the person who wants it colder pay for the extra.
• Common areas. Lights, the refrigerator, and the router belong to everyone, so they stay in the even portion of the split.

When a dispute does happen, the measured number settles it. Pull the smart plug reading, show the kilowatt-hours, and the conversation moves from opinions to arithmetic.