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How to Calculate RUBS for Multifamily Properties

If your property doesn't have individual utility meters, you're likely paying one master bill for water, trash, electric, or gas across every unit. RUBS is how most owners recover that cost from residents in a way that's consistent and easy to explain. Here's exactly how to calculate it, step by step.

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Step 1: Start With the Master Bill

Pull the actual utility invoice for the property and billing period you're allocating. A single month's bill can be misleading, since utility costs shift with seasons, heating and cooling load, and occupancy swings. Using a 6 to 12 month average gives you a more stable number to build your allocation around, and it's the approach we recommend using regardless of which method you choose below.

Step 2: Deduct Common Area Usage

Before any bill gets split among residents, pull out the portion attributable to shared spaces, things like hallway lighting, irrigation, pool equipment, or a laundry room. Residents shouldn't be billed for utility usage they don't control or benefit from directly.

The cleanest way to handle this is as a percentage of the total bill, not a flat dollar figure. A percentage scales naturally with the bill itself, so a higher summer electric bill also means a proportionally higher common area deduction, without needing to re-estimate a flat number every month.

For example: a $10,000 monthly bill with a 10% common area deduction leaves $9,000 to be allocated to residents.

Step 3: Choose an Allocation Method

Once you know the billable amount, you need a formula to split it across your units. Three methods cover most real-world RUBS setups:

• Per Square Foot (PSF): each unit's share is based on its size relative to the total property. This fits utilities where cost scales with space, like heating and cooling.
• Per-Unit: every unit pays an equal share regardless of size. This fits flatter-cost utilities like trash, where a larger unit doesn't necessarily generate more cost.
• Per-Bedroom: each unit's share is based on bedroom count. This is a practical stand-in for occupancy-based billing, since bedroom count is stable, known data, unlike actual resident headcount, which changes month to month and is difficult to verify.

There's no rule that every utility on a property has to use the same method. Water might make more sense on a per-bedroom basis, while trash runs per-unit.

Step 4: Decide How to Handle Vacant Units

Every property has some vacancy, and RUBS needs a clear rule for what happens to a vacant unit's share of the bill. There are two approaches:

• Absorb: the vacant unit's share is calculated the same as if it were occupied, but since there's no resident to bill, that portion becomes a cost the owner absorbs.
• Reallocate: the vacant unit's share is redistributed across the remaining occupied units, so the full bill still gets collected, just spread across fewer residents.

Neither approach is universally correct. Absorb keeps individual charges more stable and predictable for residents, since one unit's occupancy doesn't affect another's bill. Reallocate ensures full cost recovery regardless of vacancy, at the cost of slightly higher, less predictable charges for occupied residents.

Step 5: Run the Calculation

Here's a full example, using Electric, allocated Per-Bedroom, with vacant units reallocated:

• Master bill: $15,000
• Common area deduction (10%): $1,500 deducted, leaving $13,500 billable
• Total bedrooms across the property: 192
• Vacant bedrooms (accounting for unit-type vacancy): 19.2
• Occupied bedrooms: 172.8
• Rate: $13,500 ÷ 172.8 occupied bedrooms = $78.13 per bedroom
• A 2-bedroom unit's monthly charge: 2 × $78.13 = $156.25

Run this same process for each utility you're billing, and you'll have a complete, defensible monthly charge for every unit type on the property.

A Note on Legal and Lease Considerations

RUBS isn't just a math exercise. Most markets require specific lease language authorizing utility billing, and some jurisdictions restrict or prohibit RUBS entirely, particularly in rent-controlled housing. Before implementing RUBS on any property, confirm your lease terms and check local regulations, or consult legal counsel familiar with your market. It's also worth checking what comparable properties are doing, since a unit that nets less after RUBS needs a different rent to stay competitive.

Doing This at Scale

Running this calculation by hand works for one utility and one unit type. Once you're allocating multiple utilities, each with its own method, common area deduction, and vacancy handling, across a full unit mix, it gets error-prone fast, and small mistakes compound across every resident's bill.

Our Multifamily RUBS Template handles this automatically. Enter your unit mix and utility bills, choose your allocation methods and vacancy handling per utility, and get a clean, auditable monthly charge for every unit type, with recovery tracking that shows exactly where collections are falling short.