Old building so none of the apartments have their own submeters and I can't afford to install them. I did some research and found that there are external power monitors (Sense, iotaWatt, etc.) that can attach to their electrical panel to monitor overall energy usage. My question is whether or not it would be legal to charge our tenants based on the information provided by these devices as opposed to a submeter. We don't currently have any tenants so it would also be possible to work some language about this into the lease. Any help would be appreciated!