Wi-Fi and electricity in a flatshare: a fair split with no arguments

The flatshare and the bill moment

There's a moment in the life of every flatshare that defines cohabitation as a whole. It isn't cleaning the bathroom or the weekend noise, it's that day of the month when the electricity, gas and Wi-Fi bills arrive and someone has to write in the group "guys, this comes to X each". If all goes well, nobody replies and the transfer lands within a day. If it goes badly, the questions start. "But why so much?" "Were you here the whole month or what?" And two weeks later, the flat is no longer a flat, it's an assembly of badly matched co-owners.

The problem isn't the money. Seventy euros of electricity between three isn't a catastrophe either. The problem is the feeling, fair or not, that someone is paying for someone else's comfort. And in a flatshare the feeling weighs more than the calculation: if you sense you're overpaying, even by five euros, you'll take it to bed with you.

Flatmates usually agree a scheme in the first few days, almost always the simplest possible: divide everything by the number of people. It works for the first three months. It works until one starts working from home five days a week, another chains together night shifts away from home, and the third spends half the month at their partner's place. That's when the equal-share model starts to hurt, even if nobody says so.

Why "equal shares" cracks the moment life changes

The equal share rests on one assumption: that everyone in the flat uses the home equivalently. It's a comfortable assumption but rarely true. Electricity is consumed when someone is switching things on. Wi-Fi gets loaded when someone is using it. Gas, above all, depends on showers, washing machines and heating, which are strongly individual.

A person who works from home nine hours a day, with their monitor, their lighting and their local heating, is going to push electricity consumption up significantly. One who only appears at home to sleep will push it up much less. And yet both pay the same. Multiply that across twelve months and three flatmates, and you understand why flatshares turn over so much.

On top of this comes a variable almost nobody discusses: the size of the room. In many flats there's one big room with a balcony and two small interior ones, and the rent is usually priced accordingly. But the electricity and heating aren't, unless the group explicitly decides so. The person in the big room pays more to sleep and less to light and heat. Is that fair? It depends on the model the flat has agreed.

Three splitting models that do fit

1. Pure equal shares

This is the default model and, paradoxically, the most reasonable when everyone in the flat has a similar usage pattern. Three students who spend the morning in class and the afternoon at home studying are going to have similar consumption; fighting over tenths of a euro makes no sense. Here the equal share minimises friction.

The sign that this model fits is that you've been in the flat six months and never once thought about whether you're paying fairly. If that's true, don't touch anything.

A plausible example: an electricity bill of 78 euros between three flatmates. Each pays 26. The operation takes eight seconds. The peace lasts a month.

2. Proportional to actual usage

When usage patterns are clearly different, you have to measure or estimate. The most rigorous option is to count days of presence or days of working from home and apply a factor. If in one month one person works from home twenty days and the other two only five each, the hours of intensive use aren't split equally. A simple formula: 50 per cent is split in equal parts (it's the baseline, everyone lives there) and the other 50 per cent is split proportionally to the days of active presence.

On an electricity bill of 78 euros: 39 euros are divided among three at 13 euros each. The other 39 are divided weighted by presence. If one accumulates twenty days and the others five each, the first takes on 26 of those 39, the other two take on 6.50 each. Total: 39 euros for the work-from-home person, 19.50 for each of the other two. There's still monthly peace and now the split reflects reality.

The catch: you have to keep a record. If the discipline of marking days doesn't exist, this model collapses by the second month and reverts to the previous one out of fatigue.

3. Proportional to room size

This is the most underused option. In flats where the room differences are large, splitting electricity and gas proportionally to the square metres or to each room's rent has a clear logic: whoever occupies more space heats and maintains more space. It applies especially well to gas (heating and hot water) and to electricity, less so to Wi-Fi (which isn't consumed by the square metre).

It works in stable flats where nobody wants to open the usage conversation every month. It's stable, predictable and hard to argue with once agreed.

The Wi-Fi detail: separate from the rest

Wi-Fi deserves a different conversation. The monthly fee is fixed (it doesn't depend on usage, except in capped plans that barely exist any more) and, within the flat, the marginal cost of an additional user is basically zero. The per-head split makes far more sense here than for electricity. Same flatmates, different split on different bills. There's nothing wrong with mixing models: what goes wrong is a lack of clarity about which model applies to which bill.

One nuance: if someone in the flat consumes data massively (continuous downloads, 4K streaming all afternoon) and that forces a more expensive plan than the rest would need, the split can tilt there: the base fee is split in equal parts and the extra cost of the premium plan is borne by whoever drives it.

How to close out the month without corridor conversations

The only thing worse than an unfair split is a fair split nobody knows how it was calculated. Any decent flatshare system should let you log each bill once, assign the splitting model that applies to that bill and leave each flatmate's balance visible to everyone. ControlarGastos does exactly that, and it splits the cents by largest remainder, not by truncation, so nobody always carries the extra cent that a truncation would otherwise pin on them month after month.

What changes with a system like this isn't the final figure, it's the trust. The one who doubts stops doubting, the one who felt they were overpaying confirms they aren't, and the one on night shifts understands why they pay less this month. Transparency kills the micro-arguments before they're born.

Conclusion: a flatshare isn't a democracy, it's a contract

Splitting electricity and Wi-Fi looks like a minor detail, but it's the thermometer of cohabitation. A flat that agrees the model in the first month, writes it down (even if it's on a sheet stuck to the fridge) and respects it is a flat that lasts for years. One that improvises with each bill is a flat that turns over in twelve months, without anyone knowing why nobody sticks around.

You don't need the perfect model. You need the explicit one.