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.

  • I take it putting in individual air-to-air heatpumps for the apartments isn't an option? Also, do you already have BTU meters fitted for the existing heating system? Jul 4, 2021 at 15:33
  • We have considered that option but left it. I never heard of BTU meter, but mine doesn't have one, and doubt anyone else has one. Essentially every apartment right now has its own heater and own circuit to the radiators.
    – wfhets
    Jul 4, 2021 at 15:51
  • You will have a very unusual setup with a central heatpump and several (individual) gas heaters. Before irreversibly committing to it, talk with the various possible suppliers of the heatpump and the (existing?) heaters to see if the control systems can actually handle such a setup. You probably don't want the heatpumop to be running 24/7/365 but only when there is an actual heat demand from one (or more) of the apartments. Jul 4, 2021 at 17:12
  • I'm not sure I understand the setup of the hybrid system. Does the heat pump feed the same radiators with the gas heaters? Are the two heat sources connected in series like "warm water from heat pump → gas booster heater → radiators → cold return to heat pump"?
    – TooTea
    Jul 8, 2021 at 8:53

2 Answers 2


you could install 3 way valves prior to each water meter. When the heating for that apartment is turned off the water bypasses that apartment. This would solve the getting free heat issue if I understand how the system is plumbed.

  • That could be a solution, but I realised one apartment could just lower the temperature and still take advantage.
    – wfhets
    Jul 4, 2021 at 15:48

I would suggest you simply use water meters for each apartment, then ratio the bill according to the amount of hot water that each apartment used. Keep a small percentage in a kitty so you can pay for repairs and maintenance for the system. This may not be perfect but it will be close. No worry about who shuts down early and who doesn't.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.