A RUBS calculation (ratio utility billing system) divides a property's master-metered utility bill among residents by formula rather than by meter. The ratio utility billing formula is: (master bill − common-area deduction) × resident's allocation factor ÷ sum of all allocation factors. The factor can be the unit, the occupants, the square footage, or a blend, and that choice moves a resident's bill by up to 50%.

Here is what that looks like on one bill.

One $14,000 bill, one resident, four different amounts

The building: 120 units, 96,000 rentable square feet, 240 residents on leases. This month's master water and sewer bill is $14,000. After a 10% common-area deduction (explained below), $12,600 is allocable.

The resident: a two-bedroom unit, 1,000 sf, three people on the lease.

Same bill, same apartment, same three people. The number on the invoice ranges from $105 to $157.50 depending on a choice the resident never made. Run it the other way: a single occupant in the same 1,000 sf unit pays $52.50 under the occupant method and $131.25 under square footage.

That spread is the whole subject. The method has to be chosen deliberately, written into the lease addendum, and applied identically every month. Switch from per-unit to per-occupant in June and a family's water bill goes up by half with no change in what they used. They will ask why, and "we changed the formula" is not an answer that holds up.

If you're still deciding between RUBS and submetering, that's a different question, covered in our guide to RUBS vs submetering. The rest of this post assumes RUBS and explains where each of the four numbers comes from.

Why each method gives the number it does

• Per unit ($105.00): Every unit is one share. Simple to explain, simple to reconcile, and blind to the fact that a family of four uses more water than a single person. It suits buildings where units are uniform and it under-recovers from large households.

• RUBS by occupants ($157.50): Each resident on the lease is one share, so this unit's three people take 3/240 of the bill. It tracks water and sewer usage better than any other single factor. Its weakness is the data: occupancy comes from the lease, residents add roommates without telling the office, and a stale count shifts cost onto the households who reported honestly. Refresh occupancy at every renewal and require notification in the addendum.

• RUBS by square footage ($131.25): The unit's 1,000 sf is 1/96 of the building. Square footage doesn't drive water consumption, so this method is the wrong one for a water bill; it's the right one for gas heating and HVAC electricity, where consumption follows space. It also punishes the single occupant in a large unit.

• Hybrid ($144.38): Half the occupant share plus half the square-footage share. Used on combined bills or where a building mixes studios with three-bedrooms, because it tempers both distortions. Its cost is explainability: the addendum has to state the exact weighting, and the resident's statement has to show both halves.

• A fifth approach worth recognising because residents see it on other properties' bills: the occupant-factor method, where units are weighted by occupancy band (1 person = 1.0, 2 = 1.6, 3 = 2.2, 4 = 2.8 is a common scale) on the theory that each additional person adds less than the last. It produces a figure between per-unit and per-occupant. If a third-party billing bureau runs your programme, ask which scale they use.

• The practical rule: allocate water by occupants or hybrid, gas and HVAC electricity by square footage, and if utilities arrive on one combined bill, hybrid.

The common-area deduction: the step before any method

The 10% that came off the $14,000 before allocation is the share of the bill residents shouldn't pay: irrigation, pool, clubhouse, laundry room, leasing office, vacant units. If those areas have their own meter, subtract the actual reading. If they don't, apply a documented percentage, typically 5–15% for water depending on landscaping and amenities, and write down how it was set: an engineer's estimate, a period of separate metering, or a benchmark for the property type.

This step gets skipped more than any other, and it's the first thing a regulator or a resident's lawyer looks for. A tenant billed for the pool has a legitimate complaint, and in states that regulate RUBS, a legal one. The deduction is also the reason the total invoiced to residents will always be less than the master bill; that gap is the landlord's, by design.

Vacant units need a stated rule. Under per-unit and square-footage methods, a vacant unit's share is normally excluded from the denominator and absorbed by the landlord, not spread across occupied units. Under the occupant method, vacancy handles itself because an empty unit has zero occupants. Whichever rule applies, keep it constant; a denominator that includes vacant units in March and excludes them in April produces a share that moves for no reason the resident can see.

The RUBS admin fee

Most programmes add a monthly administrative fee per unit for the cost of reading, calculating and billing, typically $2.50 to $5.00. It appears on the invoice as its own line. On the example resident's per-occupant bill: $157.50 allocation + $3.50 admin fee = $161.00.

Some states cap the fee as a dollar amount, some as a percentage of the allocated charge, and a few prohibit it. In every regulated state the combined amount billed to all residents (allocation plus fee) may not exceed the master bill plus the permitted fee, which is why the common-area deduction has to be real rather than nominal. The state-by-state rules start with our post on whether RUBS is legal in Texas.

Reconcile before you invoice

The sum of every resident's allocation must equal the allocable bill. If it doesn't, the denominator is wrong somewhere: a unit's square footage is missing, an occupancy count is stale, or vacant units are being handled inconsistently. Rounding across 120 units can also push the total over the master bill, which is a compliance problem in regulated states and a fairness problem everywhere.

One more thing to reconcile: prior-period adjustments from the utility. If the provider re-bills or credits an earlier month, allocate that adjustment to the period it belongs to or show it as a separate line. Burying it in the current month's master bill changes every resident's share for a reason none of them can trace.

What locks the method in: the utility addendum

The calculation is only as defensible as the lease addendum that describes it. The addendum should state which utilities are allocated; the method, including the exact weighting for a hybrid; the common-area deduction and how it's determined; the admin fee; how occupancy is determined and updated; the treatment of vacant units; the billing cycle and due date; and the resident's right to see the master bill and the calculation. Several states require additional disclosures, and some require the formula to be filed with or approved by a regulator.

"Utilities allocated by landlord's formula" is not an addendum. It's unenforceable in some states and an argument in the rest. The test: can a resident reproduce their number from the addendum and a copy of the master bill? If not, the addendum isn't finished.

Running RUBS in NetSuite

A RUBS calculation is a monthly routine with five inputs (master bill, common-area deduction, method, allocation factors per unit, admin fee) and one output per resident. It goes wrong when the inputs live in a spreadsheet rebuilt each month and the occupancy column was last touched in March.

When utility billing runs inside the property management system on NetSuite, the master bill is entered against the property, the method and deduction are configuration on the property's utility setup, occupancy and square footage come from the lease and unit records, and the routine produces one charge per lease plus the admin fee, reconciled to the master bill before anything posts. The charge lands on the resident's regular invoice through the same receivables flow as rent, and the calculation is stored against the period so "how did you get this number?" is answered from the record. That's how RIOO's resident utility billing handles it, with the NetSuite utility billing and meter management setup behind it.

The test for any system: change one unit's occupancy from two to three and rerun the month. Every other unit's occupant-based share should move down slightly. If only the one unit changed, the denominator isn't being recomputed, and the reconciliation will fail.

Frequently asked questions

Q1. How is RUBS calculated?
Subtract the common-area share from the master utility bill, then allocate the remainder to each unit by the method in the lease addendum: equally per unit, by number of occupants, by square footage, or by a weighted blend. Add any permitted administrative fee as a separate line. The sum of all allocations must equal the allocable bill.

Q2. What is the most common RUBS allocation method?
For water and sewer, per-occupant or a hybrid of occupants and square footage, because usage follows people. For gas and electricity used for heating and cooling, square footage, because usage follows space.

Q3. What is a common-area deduction in RUBS?
The portion of the master bill attributable to areas residents don't occupy: irrigation, pools, clubhouses, laundry rooms, vacant units and offices. It's removed before allocation, either from a separate meter reading or as a documented percentage, and the landlord absorbs it.

Q4. Can a landlord charge an admin fee on RUBS?
In most states, yes, as a fixed monthly amount per unit stated separately in the lease addendum. Some states cap it or prohibit it, and none allow the total billed to residents to exceed the master bill plus the permitted fee.

Q5. Why did my RUBS bill change when my usage didn't?
Because RUBS allocates the building's total bill, a resident's share moves when the master bill moves, when occupancy elsewhere in the building changes the denominator, or when the common-area deduction is adjusted. The method and its inputs should be in the utility addendum so the change can be traced.

Related reading

• RUBS vs submetering: which utility billing method is right for your property
• NetSuite utility billing and meter management for property management
• Resident utility billing system