RoomProrateShould a roommate who was away pay less of the utility bill?
Updated 2026-11-01
The situation comes from a question on r/Roommates (October 2026). The amounts are a fictional bill run through the RoomProrate calculator on 1 November 2026.
Six graduate students share a house. One of them, Sam, was away for ten days and asks to pay less of this month's electricity. The others point out that the fridge, the router and the rest of the house kept running. Both sides have a point, so it helps to see the actual numbers.
Two ways households answer it
- Count the trip as time living there. Sam still has a room and belongings in the house, and the fixed part of the bill does not stop. Everyone pays the same share.
- Leave the trip days out of usage. Sam's share of the usage follows the days Sam was actually there. The fixed part is still shared by everyone.
One reply in that thread suggested prorating only when someone actually moves in or out, and splitting evenly while a person still has a room in the house. That is one household rule, not a requirement. Whatever you choose, use the same rule for every person and every trip.
Worked example: six roommates, one 10-day trip
November electricity, 1 to 30 November (30 days): fixed service charge 15.00 and usage 180.00. Sam is away from 10 to 19 November, which is 10 days. The fixed charge is shared by all six in every column.
| Person | Trip counted | Trip left out, daily split | Trip left out, person-days |
|---|---|---|---|
| Each of the other five | 32.50 | 34.50 | 34.26 or 34.27 |
| Sam | 32.50 | 22.50 | 23.68 |
Counting the trip, everyone pays 2.50 fixed plus 30.00 usage. Leaving it out with the daily split, each day's usage of 6.00 is shared by five people instead of six on the ten trip days, so each of the other five pays 1.20 instead of 1.00 on those days: 2.00 more each, and 10.00 less for Sam. With person-days, the 180.00 is shared over 170 person-days instead of 180, and the leftover cents are handed out by the calculator's rounding rule. Each column adds up to 195.00.
How to enter a trip in the calculator
- Add the five who stayed with 1 November as the first day and no last day.
- Add Sam twice: "Sam before trip" from 1 to 9 November, and "Sam after trip" from 20 November with no last day.
- Add the bill: 1 to 30 November, usage 180.00, fixed 15.00. For the fixed charge, tick the five and only one of Sam's two rows.
- Calculate and add Sam's two totals: 11.50 and 11.00 make 22.50 with the daily split.
Before you decide
- Decide the rule before anyone sees the bill. A trip by one person this month can be someone else's trip next month.
- Keep the fixed part shared whichever way you go; it is the cost of keeping the account open. See fixed charges and empty days.
- Neither column measures who used more power. A space heater left on is a different conversation.
- This page does not cover what your lease or the supplier's contract requires.
If the whole house is empty for weeks, see who pays when everyone is away over the break.
Questions
Should I pay utilities if I wasn't there?
It depends on what your household agreed. Some households treat a trip as time living there, because the room, the fridge and the fixed charges keep costing money while you are away. Others leave trip days out of the usage part. In the example on this page, a 10-day trip changes the traveller's share from 32.50 to 22.50 with the daily split. Agree on the rule before the bill arrives.
How do I leave a trip out in RoomProrate?
Add the person twice: once with the days before the trip and once with the days after it. Tick only one of the two rows for the fixed charge, otherwise that person pays the fixed part twice. Then add the two totals together.
See all guides.