Utility bills among roommates: equal vs proportional

Equal split or proportional? It's the question that surfaces every winter when the heating bill triples and one flatmate runs their bedroom radiator while another wears jumpers and resents them.

TL;DR

Default to equal split for utilities; switch to proportional only when usage is genuinely and persistently unequal, and only after you've had the conversation. Don't install sub-meters - they cost more than the disagreement.

The case for equal split

Most utilities (gas, electricity, water, internet, council tax) are dominated by what economists call "shared overhead" - costs that don't scale with one person's usage. The flat's boiler runs to heat communal areas; the router runs whether one person is streaming or four. Charging by use understates these shared costs and overstates individual usage.

Equal split is also the only model that doesn't require measurement. Sub-meters cost £200+ per circuit; smart-plug tracking is fragile; "I think you used more" is unverifiable. Equal split skips all of that and is fair on average.

The case for proportional split

Proportional makes sense in two specific cases:

• One flatmate works from home, the rest don't.The work-from-home flatmate runs heating from 9am to 5pm for themselves; the rest only get heat from 6pm onwards. Across a winter, that's a real difference.
• One flatmate has a markedly different usage pattern.Long showers, a bedroom heater, a gaming PC running 24/7. Once per week is normal variance; daily it's a real cost.

In both cases, the right move is a flat top-up - "Sarah pays £20 extra for utilities to reflect the WFH heating" - not meter-by-meter accounting.

We have a deeper take in what if one roommate uses way more electricity?

What about internet and streaming subscriptions?

Equal split, always. The marginal cost of one more person on a £40/month broadband connection is zero. Same for Netflix, Spotify Family, the gym pass.

What about council tax?

Equal split. Council tax is per-flat, not per-room. A bigger bedroom doesn't pay more council tax than a smaller one. (We covered the rent-by-room-size question separately in how to split rent fairly when rooms aren't equal.)

How to set up the conversation if you want to switch

Don't announce "we're going proportional now". Frame it as a check-in:

"I've noticed the heating bill is much higher this winter - probably because Sarah's been working from home? I think it's fair for the WFH person to pay a bit more during winter months. Maybe £20 extra on the December and January bills? Open to other ideas if that doesn't feel right."

What we'd do differently

Don't try to backdate adjustments. If you've been equal-splitting for six months and want to switch to proportional, start from next month, not from October. Retroactive changes feel like accusations.

Try it

Create a flat group when you move in. Log every utility bill as it arrives. The history is the evidence if a switch ever needs to happen.