# How to split utilities in a duplex with one meter

Canonical URL: https://www.evenoutapp.com/guides/split-utilities-in-a-duplex
Updated: 2026-10-06

Split a duplex's shared utility bill by household, using a rule both households accept. Equal halves suit similar households, occupants or square footage suit different ones, and a sub-meter reading is the most exact. On a $240 electric bill with 3 people in one unit and 1 in the other, occupants give $180 and $60, against $120 each at 50/50.

Key points:
- With one meter and two households, the unit of the split is the household. A 50/50 split charges a lone occupant $120 where each person next door pays $40.
- On a $240 bill, Unit A pays $120 at 50/50, $132 by square footage, $156 by sub-meter reading and $180 by occupants.
- Water follows people and heating and cooling follow floor area, so one workable mix is occupants for water and square footage for electric and gas.
- Rerun the shares whenever occupants change. A fourth person in the 3-person unit moves a $240 bill to $192 and $48.

## Why is the household the unit of the split?

In a duplex with one utility account, the bill arrives in one name and the other household repays its part. That makes the question one of households, not people. A 50/50 split sounds fair until the households differ in size.

Say a duplex has 3 people in Unit A and 1 person in Unit B, and the electric bill is $240. At 50/50 each unit pays $120. Unit A's three people pay $40 each and Unit B's one person pays $120. Split per person instead and each of the 4 people pays $60, so Unit A pays $180 and Unit B pays $60.

Whether one household may bill another this way depends on the lease and local law. This page covers arithmetic and gives no legal advice.

## What are the four ways to split it?

The rule changes Unit A's share of a $240 bill by as much as $60. Here are the four rules on the same bill. Unit A has 3 occupants and 1,100 square feet. Unit B has 1 occupant and 900 square feet. For the last row, say the main meter reads 1,500 kWh and a sub-meter on Unit B reads 525 kWh, so Unit A used the other 975 kWh.

| Rule | Shares | Unit A / Unit B |
|---|---|---|
| 50/50 | 1 and 1 | $120 / $120 |
| By occupants | 3 and 1 | $180 / $60 |
| By square footage | 1,100 and 900 | $132 / $108 |
| By sub-meter reading | 975 and 525 kWh | $156 / $84 |

Each row is the bill times a household's share of the total. For square footage, 1,100 / 2,000 = 55%, and 55% of $240 is $132. For the sub-meter row, 975 / 1,500 = 65%, and 65% of $240 is $156.

The last rule needs a second meter, which a duplex with one meter does not have. Electric utilities measure electricity in kilowatthours (kWh) and use meters to track how much each customer uses. If one unit gets a sub-meter, its reading gives you a number to split by, and the split follows real use. For water, see [what a water submeter is](https://www.evenoutapp.com/glossary/water-submeter).

## Which rule fits which bill?

Pick the rule for each bill by what drives its use. The U.S. Energy Information Administration reports that in 2020 the three largest uses of residential electricity were air conditioning at 19%, space heating at 12% and water heating at 12%. Heating and cooling tend to follow the space being heated and cooled, and hot water tends to follow how many people use it.

- **Water:** by occupants, since it follows people.
- **Electric and gas:** by square footage, since heating and cooling follow floor area. Occupants are a fair second choice if the units are close in size.
- **Internet and other flat bills:** 50/50, since the price does not change with use.

Say one month's water is $90, electric is $240 and internet is $60. That mix gives Unit A $67.50 for water by occupants, $132 for electric by square footage and $30 for internet, a total of $229.50. Unit B pays $22.50, $108 and $30, a total of $160.50. Together they pay the $390 in bills.

## How do you set up the split step by step?

1. **Write down each household's numbers.** List people, square feet and any sub-meter readings.
2. **Choose a rule for each bill.** Write the choice somewhere both households can see it.
3. **Turn each number into a percentage.** Divide a household's number by the total of both.
4. **Apply the percentage to the bill.** $240 x 55% = $132.
5. **Check it when something changes.** New occupants, a long absence or a new sub-meter all change the numbers.

[How to split utilities](https://www.evenoutapp.com/guides/how-to-split-utilities) walks one month of bills through four methods for roommates in one apartment. For water alone, see [how to split a water bill](https://www.evenoutapp.com/guides/split-water-bill). The electric and gas side is in [how to split electric and gas bills](https://www.evenoutapp.com/guides/split-electric-and-gas-bills).

## How do you track it in EvenOut?

Make a "Household" group with one person from each household, and set the household that holds the account as the payer. Add each month's bill, choose "Shares" in "How to split" and type 3 and 1 for occupants. The pill reads 4 shares with the value of one share, $60, and each person's amount shows under their name. For square footage, type 1100 and 900 instead.

Utility bills change every month, so add each one as it arrives. "Repeat" copies the same amount and split each time, which suits a flat bill such as internet. The other household taps "Settle up" and "Record payment" when they pay. EvenOut records who owes what and does not move money.

## What should you do next?

Run your last real bill through the four rules before you pick one. If the answers are close, take the simplest. If they are far apart, as they are for the 3-person unit above, choose the rule that matches what the bill measures. The [split utilities by usage calculator](https://www.evenoutapp.com/tools/utilities-split-by-usage-calculator) separates the fixed charges from the usage part of a bill, which helps when only some of the charges follow use.

## Frequently asked questions

### Should the split change when someone moves in or out?

Yes, from the first full bill after the change. Say the 3-person unit gains a fourth person while the other unit stays at 1. The occupant shares go from 3 and 1 to 4 and 1, so a $240 bill splits $192 and $48 instead of $180 and $60. Write the rule down once so nobody has to renegotiate each time.

### What if one household is away for part of the month?

Count occupant-days instead of occupants. Say the single occupant is away for 15 of 30 days. The 3-person unit has 3 x 30 = 90 occupant-days and the other unit has 15, a total of 105. On $240 that is $205.71 for the larger unit and $34.29 for the other, which adds back to $240.00.

### What if the two households cannot agree on a rule?

Average two rules. For the 3-person unit, 50/50 gives $120 and occupants give $180, so the midpoint is $150, and the other unit pays $90. In EvenOut, the Exact amounts split lets you type $150 and $90 and shows All assigned when they add up to $240. Review the midpoint after a few months of real bills.

## Sources

- [U.S. Energy Information Administration: Measuring electricity](https://www.eia.gov/energyexplained/electricity/measuring-electricity.php)
- [U.S. Energy Information Administration: Electricity use in homes](https://www.eia.gov/energyexplained/use-of-energy/electricity-use-in-homes.php)