I've lived with tons of roommates the last 5 years and do not see the utility in this... There are jut too many factors to take into consideration. We are currently in a 4-bedroom house with other amenities. Two of the bedrooms are very small, and two are large. First, each room starts at a base amount to take into consideration the shared spaces... Which is $50 for us. So... $700/mo. total - $200/mo. for all 4 rooms = $500/mo. leftover. Then we split the rooms into amounts that we agreed seem fair based on the sizes. As a median, $500/4 = $125. The large rooms are $165, small rooms are $85. Add in the $50 from before and we have:

Large Room: $215 Large Room: $215 Small Room: $135 Small Room: $135

Basically, you're paying a base price for the shared space, then an additional price for the approximate square footage of your room. We avoid going into exact measurements to keep it simple.

As far as utilities go, it was a nightmare to organize them every month and collect what everybody owed, especially when people started owing over a couple months past. Making sure to record payments, update the balances, ask for payments, pay all the bills, and sometimes organize which bills get paid first because we owed was a disaster.

So, for utilities, I calculated the yearly average of all of them divided by the minimum number of roommates (4 in our case), added ~10-15% on the top, and that was our new monthly utility bill. Everybody pays the same amount every month. Rent is due on the 1st. Utilities are due on the 15th. I track payments using Google Docs so they have access.

Also annoying was the process in which people bought supplies for the house and wanting reimbursements... Sometimes people would buy the same things and we'd have a stock of them, etc... So that extra cushion in the utilities goes toward purchasing house supplies in bulk.

All of the money goes into a PayPal student account with a debit card. Everybody has access to Mint.com to see transactions/balance, but only I have access to the actual account. Anybody can use the debit card, and I get text/email alerts for every transaction. If we end up having a large balance, we can improve something in the shared spaces or repay debts from roommates that had to be kicked out for owing (face it... that money is gone - Always collect a security deposit!).

We believe this system is fair and scaleable, as it rewards people for sharing rooms rather than making them pay more for the same space... But as the number of people grows, the cushion in the utilities grows to a larger percentage... Making it possible to improve our shared space living conditions as a reward for putting up with too many roommates. For instance, supplying everything we need for a full garden in the back yard, etc.

I apologize for this long-winded explanation, but I hope this helps somebody. Compared to the way of normally splitting up a house, this is much simpler. Everybody knows what they pay in rent for their room, they know how much they'd pay if they moved their partner in, they know how much utilities are, and everything is transparent.

The main thing I haven't figured out is chores/shared duties outside of just cleaning up after yourself. We have a whole 100+ year-old house to maintain/rehab, and there is a lot to do. Working on some kind of system where people can choose from a revolving list what chores they want to do to accumulate their points. First come, first choice. HabitRPG looks promising in that you can get groups together and tasks go up in value the longer they aren't done.

Also, having repercussions for late-payments/lack of chores. We're not big on charging interest/fines to those that cannot afford it already... But will soon be experimenting with taking away access to house amenities... For instance, the upstairs (nicer) bathroom, the high-speed Internet, our shared access to the local Hackerspace, etc.