Your landlord seems to have a reasonable approach to charging for utilities. Frequently on this advice blog I will see where landlords charge tenants a fee on top of actual costs. So, if your landlord is taking the actual cost and charging you based on square footage, it is considered reasonable and legal.

If you feel there is a some discrepancy in their utility billing practices, you can always request an audit. But, that may require some type of a formal legal action such as filing a complaint with the RPA.

Sounds like the way you are being billed for utilities is reasonable, although its not the most accurate way. It would be far better to have separate meters installed. However, due to the cost required to install such devices, it will probably never be done at your property. Most new rental communities now have separate meters to individually bill tenants based on their consumption rather than their square footage.