RUBS Utility Billing Formula: How It Works

RUBS (Ratio Utility Billing System) splits one master utility bill among units using a ratio instead of individual meters. The basic formula is: unit's share = (unit's factor "÷" building's total factor) × the bill, where the factor is occupant count, square footage, or a blend of the two. You bill each tenant their share as a separate line item, and the total you collect can't exceed what you actually paid the utility company. Some states and cities restrict or ban ratio billing, cap administrative fees, or require specific disclosures "—" check your state and city rules before you start.

The three common RUBS formulas

All three divide the same bill. They differ only in what drives the ratio.

• Occupant-based: best for water, sewer, and trash, since usage tracks with how many people live there.
• Square-footage-based: best for heat and sometimes common-area electricity, since larger spaces cost more to condition.
• Hybrid (weighted): often half occupants and half square footage, used when you want one formula for a mixed bill or to soften the hit on a large unit with one tenant.

Occupant-based RUBS usually counts children differently than adults "—" a common convention is to count each adult as 1.0 and each child as 0.5, because children generally use less water. Whatever you choose, write it down and apply it the same way to every unit. Inconsistent occupant counting can look like discrimination against families with children, which the federal Fair Housing Act prohibits.

A worked fourplex example

Say you own a fourplex on one water meter. The city bills you for water, sewer, and trash together, and last month's bill came to $520. The units look like this:

Unit	Size	Square feet	Occupants
1	1-bed	650	1 adult
2	2-bed	900	2 adults
3	2-bed	900	2 adults, 1 child
4	1-bed	650	1 adult

Step 1: Pick the factor

This is a water/sewer/trash bill, so occupant-based makes the most sense. Using 1.0 per adult and 0.5 per child:

• Unit 1: 1.0
• Unit 2: 2.0
• Unit 3: 2.5
• Unit 4: 1.0

Building total: 6.5 occupancy units.

Step 2: Carve out what isn't tenant usage

You run a shared laundry room and an outdoor spigot you use for the lawn. Billing tenants for landlord-controlled usage is the fastest way to get an argument "—" and in some places it's not allowed at all. So you hold back a common-area allowance of 10%, or $52, and absorb it yourself.

Billable amount: $520 "−" $52 = $468.

Step 3: Run the ratio

Each unit's share = (its factor "÷" 6.5) × $468.

Unit	Factor	Share of total	Amount billed
1	1.0	15.38%	$72.00
2	2.0	30.77%	$144.00
3	2.5	38.46%	$180.00
4	1.0	15.38%	$72.00
Total	6.5	100%	$468.00

You collected $468 against a $520 bill. You're out $52, which is exactly the point "—" you're recovering tenant usage, not profiting on utility resale. Reselling utilities above cost can put you in territory regulated by your state's utility commission.

Step 4: Bill it

Rent for Unit 3 is $1,450. The tenant's statement reads:

• Base rent: $1,450.00
• Water/sewer/trash (RUBS, 2.5 of 6.5 occupancy units, August bill $520 less 10% common area): $180.00
• Total due: $1,630.00

That level of detail is the difference between a charge a tenant pays and a charge a tenant disputes. Keep a copy of the city bill with your records each month so you can show the math on request. If you track income and expenses per lease "—" in Rentmark or a spreadsheet "—" log the $520 as an expense and the $468 as utility income so your Schedule E reflects reality.

What goes in the lease

RUBS only works if the tenant agreed to it in writing before move-in. Your utility clause should spell out:

1. Which utilities are billed by RUBS and which are the tenant's own account.
2. The exact formula, including how adults and children are counted and the square footage used.
3. The common-area holdback, stated as a percentage or a flat deduction.
4. Any administrative fee, if your state allows one at all "—" many cap it or prohibit it.
5. When the bill arrives and when it's due, and whether unpaid utility charges are treated as rent or as a separate debt. That distinction matters for how you can enforce it.
6. Occupancy change notice, so the factor updates when someone moves in or out.
7. Your obligation to show the master bill on request.

If you're drafting from scratch, start from a state-specific lease agreement rather than a generic template, because utility billing disclosure requirements vary a lot. It also helps to settle the broader question of who pays which utilities in a rental before you decide RUBS is the right tool.

One more point: don't touch the security deposit to cover an unpaid utility balance unless your lease and your state's deposit rules clearly allow it and you follow the required itemization process.

If the building is heated by one boiler instead

Change one fact and the formula changes with it. Say the same fourplex has a single gas boiler and the January gas bill is $640. Occupant count is the wrong driver here "—" a 900-square-foot unit costs more to heat than a 650-square-foot unit regardless of how many people sleep in it.

Switch to square footage. Total conditioned space is 650 + 900 + 900 + 650 = 3,100 sq ft. Hold back 8% ($51.20) for the heated hallway and basement, leaving $588.80 to allocate:

• Units 1 and 4: 650 "÷" 3,100 = 20.97% × $588.80 = $123.47 each
• Units 2 and 3: 900 "÷" 3,100 = 29.03% × $588.80 = $170.93 each

Note that Unit 3 now pays less than Unit 2 did under the occupant method relative to its neighbors "—" because heat follows space, not people. Running two different formulas in the same building is fine, as long as the lease names both and ties each to its own bill.

A second "what if": if your units are separately metered or submetered, skip RUBS entirely. Actual measurement is more defensible and generally better received by tenants. Submetering also tends to reduce total consumption, because people who see their own usage use less. For a two-unit property, compare the four ways to split utilities in a duplex before you commit to a ratio.

Where RUBS can get you in trouble

• Local bans and restrictions. Certain states and cities limit ratio billing for water, require submeters in new construction, or impose disclosure and record-keeping rules. A few prohibit it outright for specific utilities.
• Collecting more than you paid. If your allocations total more than the master bill, you're reselling a utility.
• Mid-lease changes. You generally can't convert an existing all-utilities-included lease to RUBS before renewal without the tenant's agreement.
• Occupant counting that penalizes families. Charging more per child than per adult, or counting children at full weight when you discount other factors, invites a fair housing complaint.
• Charging for your own usage. Vacant units, landscaping, and common laundry belong on your side of the ledger.

This is general information, not legal advice "—" confirm what your state and city allow before you add a RUBS charge to any lease.