I live in a shared apartment complex with 6 apartments (~400m2) which are currently being heated by 6 individual gas heaters and paid individually, you pay what you use. We are interested in investing in a water heat pump (air to water) to lower the heating cost, but keep the gas heaters as the heat pump will not be enough. So essentially creating a hybrid system.
It is important that the cost of usage is split fairly depending on usage. Every apartment will have one water meter. We can then calculate the cost for apartment X as total water circulation apartment X / total water circulation.
However, I believe there is a way to abuse the system (maybe there are more?). Let's say apartments X and Y are home and using the system but X decides to turn off their gas heating but keeps their individual pump running while Y is still heating his apartment. Because they are now on the same water circuit, apartment Y will also be heating apartment X without getting paid for it.
Is there any way to solve this problem?
Unfortunately we dont have the possibility to create one central heating for all apartments.