u/Delicious_Exit3715

I have a controls system installed in a building that is BACnet and I'm looking to bring all the points into Niagara to set up a new controls system with better capabilities than the one running the building now.

I want to connect to the building's network remotely so I can program in Niagara and access the points without having to be on-site and bother the customer. What's the best way to do this? VPN gateway, cellular router, other? I'd like to get something without a recurring service fee that I can just plug in and leave there.

I'm not sure what which product would be best, what capabilities to look for, price range (new to networking)