How to split electric and gas bills fairly

How do you split an electric bill when one person uses much more?

Charge the heavy device to the person who owns it, then split the rest equally. This carve-out only makes sense for something that clearly uses more than anything else in the home, such as a space heater, a window air conditioner or a gaming computer that runs all day.

Say three roommates share a $210 electric bill for 700 kWh, and one of them runs a space heater all month.

1. Find the average rate. Divide the bill by the kWh printed on it: $210 ÷ 700 kWh = $0.30 a kWh.
2. Measure the device. The heater used 120 kWh over the billing period (the next section shows how).
3. Price it. 120 kWh × $0.30 = $36.00, which belongs to the heater’s owner.
4. Split the rest. $210 − $36 = $174, and $174 ÷ 3 = $58.00 each.

Roommate	Heater	Shared part	Pays
Heater owner	$36.00	$58.00	$94.00
Roommate 2	$0.00	$58.00	$58.00
Roommate 3	$0.00	$58.00	$58.00

The three payments add back to $210.00. An equal split would be $70 each, so the heater owner pays $24 more and each of the others pays $12 less.

How do you measure what a device uses?

Plug the device into a plug-in energy monitor and read the kWh at the end of the billing period. A kilowatt-hour is 1 kilowatt (1,000 watts) of power used for 1 hour, as the U.S. Energy Information Administration defines it. Put the monitor in the wall outlet, plug the device into the monitor, and write down the reading on the first and last day of the period.

Without a monitor, estimate it: watts ÷ 1,000 × hours. A 1,500 watt heater that runs for 80 hours is 1.5 × 80 = 120 kWh. The estimate runs high for a heater with a thermostat, because the element switches itself off once the room is warm, so count the hours it actually heats, not the hours it is switched on.

A monitor fits a device on a normal wall outlet. For something wired into the wall, use the nameplate estimate or agree a flat monthly amount instead.

Agree the rule before the first bill. “Heavy” is a judgment call, so pick a cutoff the whole household accepts and write it down. A device that uses a few kWh a month is not worth carving out.

Does the fixed service charge change the math?

Slightly. Some electric bills include a fixed monthly service charge that does not change with use, and a heater does not cause it. Take it off first, split it equally, and price the device with the usage part only.

Use the same $210 bill with a $14 fixed charge. The usage part is $196, and $196 ÷ 700 kWh = $0.28 a kWh. The heater’s 120 kWh cost $33.60. The rest of the bill is $210 − $33.60 = $176.40, which is $58.80 each. The heater owner pays $33.60 + $58.80 = $92.40, and the other two pay $58.80.

For one device that moves the owner’s bill by only $1.60, so many households skip this step. It matters more when the fixed charge is large or when several devices are carved out.

How do you split a gas bill that changes with the seasons?

Split gas by who lives in the home and for how long, not by device. A furnace or water heater has no plug-in monitor, and the bill shows total use in units such as therms (the EIA defines a therm as 100,000 Btu), not who burned it.

The bigger problem is the calendar. The EIA reports that residential natural gas use peaks during the winter, so the same home can see a January bill several times its July bill. Say four roommates pay these gas bills over a year: January $190, February $170, March $130, April $80, May $45, June $25, July $20, August $20, September $30, October $60, November $80 and December $110. The year costs $960. There are three ways to settle it.

• The actual bill each month. Split what the bill says: $47.50 each in January and $5.00 each in July. It is always accurate, but winter payments are many times summer ones.
• A 12-month average. $960 ÷ 12 = $80 a month, so $20 each, all year. The account holder pays the big winter bills out of the payments saved up in summer. Ask your utility whether it also offers a level payment plan.
• By who lived there each month. Split every month’s actual bill among the people in the home that month. Use this whenever someone leaves or arrives.

The average has a catch. Say Dana holds one of the four rooms from April to September and Eli holds it from October to March. Dana’s real share is $220 ÷ 4 = $55 and Eli’s is $740 ÷ 4 = $185. Under a $20 a month plan both pay $120, so Dana overpays by $65 and Eli underpays by the same $65. Use the average only when the same people stay for all 12 months.

What if someone moves in or out mid-month?

Split the bill by days. Use the service dates printed on the bill, which rarely match the calendar month: a bill can run from October 14 to November 13, so count the days between the dates it shows.

Take November’s $80 gas bill, with three roommates there all 30 days and a fourth who moves in on the 21st, so is there for 10 days (the 21st to the 30th). That is 3 × 30 + 10 = 100 person-days, so each person-day costs $80 ÷ 100 = $0.80. The new roommate pays 10 × $0.80 = $8.00 and each of the others pays 30 × $0.80 = $24.00. The shares add back to $80.00.

How do you record this in EvenOut?

Make a Household group (“Rent and bills”) and add each bill as an expense in the Utilities category.

• A carve-out. Choose “Exact amounts” and type $94.00, $58.00 and $58.00. The pill reads “All assigned” once the amounts add up to $210.
• A split by days. Choose “Shares” and type each person’s days, such as 30, 30, 30 and 10. Each person’s dollar share shows under their name: $24.00, $24.00, $24.00 and $8.00.
• A fixed charge plus usage. Add the fixed charge as one expense with “Split equally” and the usage part as a second expense with “Shares”.
• A flat monthly amount. The $80 average can be set to Repeat monthly. A bill that changes every month is better entered by hand.

What should the household agree on first?

Write down three things before the next bill arrives: which devices get carved out and at what cutoff, whether gas is settled by the actual bill or an average, and who holds each account. The other bills follow the same logic. How to split utilities compares four methods using one household’s full month, and the split utilities calculator does the fixed-plus-usage sum for you. Water and internet have their own wrinkles, covered in how to split a water bill and how to split an internet bill.