Split a house into three flats but leave one water meter on the wall, and every quarter brings the same small fight: whose usage is this, and who owes what? A shared, or master, meter bills the landlord for the whole building, so the split is yours to make and yours to defend. Done carelessly it breeds disputes; done with a clear written rule it is routine.
This guide covers the fair ways to divide one meter across units, the math behind each, and the legal lines you should not cross.
Is it legal to put several tenants on one meter?
In most places yes, provided two things hold: you disclose the method in the lease, and you never bill a tenant more than the utility charged you. New York caps the tenant's bill at the landlord's actual cost, with only genuine administrative costs on top, and California limits recovery to actual costs and generally bars a separate water charge unless the unit is sub-metered. The principle to carry everywhere: you are allocating a cost, not selling a utility at a markup. Check your local regulations before you set a method.
How do you divide the bill fairly?
Without a meter per unit, you allocate the master bill by a formula. The industry name for this is a Ratio Utility Billing System, or RUBS, and the common bases are:
- Floor area. Each unit pays in proportion to its size. Fits utilities that scale with space, such as heating and common-area electricity.
- Occupancy. Each unit pays by the number of people living there. Fits water and sewer, which follow people far better than square metres.
- Fixtures or bedrooms. A weighting by bathrooms, bedrooms, or water fixtures, for when neither size nor headcount alone is fair.
- Equal split. The bill divided by the number of units. Simple, and defensible only when the units are genuinely alike.
You can blend them (a common mix is 70% area and 30% occupancy), but simpler is easier to defend to a tenant who queries the number. One documented effect of announcing any RUBS: usage discipline appears, and buildings report roughly 5 to 15% lower consumption once residents know the bill is shared back to them.
Worked example: one €120 water bill, three flats
Three flats share one water meter and the quarterly bill is €120. Watch how the basis changes the answer.
By floor area, the flats are 40, 30, and 30 m2 (100 m2 total), so the shares are 40%, 30%, and 30%: €48, €36, and €36.
By occupancy, the flats house 1, 2, and 3 people (6 total), so the shares are one sixth, two sixths, and three sixths: €20, €40, and €60.
Same bill, very different outcomes. Because water follows people, occupancy is the fairer basis here, and the single occupant is right to prefer it. Both splits add back to exactly €120, which is the test every allocation must pass: never round a tenant into paying for water no one used.
By area or by people, which basis should you pick?
Match the basis to what drives the utility. Water and sewer scale with occupants; heating and lighting scale with space; trash is often split equally per unit. Pick the basis a reasonable tenant would agree tracks their share, write it into the lease, and keep it consistent quarter to quarter. Switching methods whenever it suits you is how a fair system starts to look unfair.
When should you install a sub-meter instead?
A formula is an estimate, not a measurement. When one unit's real use is well out of line, a heavy user or a long-empty flat, a sub-meter measures actual consumption and settles the argument for good. It costs money to fit, and some places require it before you can bill certain utilities at all, so weigh the install against the friction a formula is causing. For a steady building of similar units, RUBS is usually enough; for mismatched units or a serial over-user, meter them.
How do you bill each unit's share and keep it late-proof?
However you split it, the share still has to reach the tenant and get paid. In FixRent you add each unit's computed share as a charge on that tenant, next to the rent, and it lands on one invoice per unit. FixRent does not do the division for you (you choose the basis and run the math), but it totals the invoice, shows who owes what across every unit, and writes the reminder for anyone late, so a shared meter never becomes a shared headache. For meter readings, fixed charges, and deposits, see the rest of the utility billing guides.