How to split utility bills with roommates

Rent is one number, agreed once. Utility bills between roommates (or flatmates, if you are British) are messier: they come in at different times, from different companies, and one roommate’s name is on every account. Somebody moves in on the 11th. Somebody runs a heater all winter. This is how to split utility bills with roommates so the split is fair and quick to work out.

Start with an equal split

For most households, an equal split of electricity, gas, water and internet is the fair answer. People’s usage differs a little, but it evens out over a year, and an equal split takes no tracking at all.

Move away from equal only when there’s a reason everyone can see:

• someone wasn’t living there for part of the billing period;
• someone clearly uses much more, such as a space heater or a full-time home office;
• a service only some of you use.

If none of those applies, don’t measure. Arguing over a few dollars of electricity costs more goodwill than it’s worth.

Splitting by days present

When a roommate moves in or out mid-month, split the bill by person-days: add up the days each person lived there during the billing period, and give each person their days’ share of the total.

Worked example. Mia and Tom have shared a flat all along. Ravi moves in on the 11th of a 30-day month, so he’s there for 20 days (the 11th to the 30th).

Person-days: Mia 30 + Tom 30 + Ravi 20 = 80. Each bill splits 30/80, 30/80 and 20/80, which is 37.5%, 37.5% and 25%.

Every row adds back to its bill exactly, and the shares add to €204.00. Mia paid €120.00 and owes €76.50, so she’s owed €43.50. Tom paid €84.00 and owes €76.50, so he’s owed €7.50. Ravi paid nothing yet and owes €51.00.

When the numbers don’t divide evenly, work in cents and give the leftover cent to one named person, the same one each time. A one-cent difference is nothing; a sheet that doesn’t add up starts arguments.

Some households split internet equally even in a partial month, because the price doesn’t change with how many people are there. That’s a fine choice too. Just agree it before the bill arrives.

Heavy users: the space heater and the home office

Sometimes one person really does drive the bill. A space heater in one bedroom all winter, a gaming PC running all night, a home office with the heating on all day while everyone else is out.

Don’t try to measure it appliance by appliance. Agree a different share for the bills it affects, and agree it once:

• Shares. For the winter months, the person with the heater takes two shares of electricity and everyone else one. On a €120 bill with three people, that’s €60, €30 and €30.
• A fixed top-up. The heavy user pays a set extra amount per month and the rest splits equally. Simpler to explain, slightly less precise.

Either is fine. What causes trouble is leaving it unspoken and then raising it in February when the bill is double. In kisir, a split by shares is one of the options on any expense, so the arrangement doesn’t have to be redone each month.

Who holds the account

One roommate usually has the electricity, gas and internet in their name, and their card is charged every month. That’s convenient, but it means they’re lending the household money until everyone pays them back.

Three habits make it painless:

• Record each bill the day it’s paid, against the person whose card paid it, for everyone it covers.
• Settle monthly, on a fixed date, rather than chasing each bill separately.
• Put the accounts in the name of whoever is staying longest. Transferring an account when someone moves out is a hassle; avoiding it is better.

Meter readings at move-in and move-out

Take a photo of the electricity, gas and water meters on the day someone moves in or out, with the date visible. It costs ten seconds and settles any argument about who used what before or after.

With readings, you can split a bill exactly. Usage up to the move-in reading goes to the old household; usage after it is split with the newcomer included. Without readings, fall back on person-days, which is close enough for most bills.

The same goes for moving out. The last bill usually arrives weeks after the person has left, so record the final reading, keep their share open, and settle when the bill lands. For the rest of what happens when a roommate leaves, deposit included, see how to split rent and bills with roommates.

Estimated bills and corrections

Some suppliers send estimated bills and correct them later. Split each bill as it arrives, and split the correction when it comes, among whoever was living there for the period it covers. Don’t go back and reopen a month everyone has already settled. The correction evens it out.