I was waiting for Sean to respond to this first, but it often is unwise to use a backup system as a main. I remember a lower manhattan telco facility (can't remember the address) that switched to backup, didn't handle the procedures correctly and ran the batteries down to zero. Took all sorts of things off line, including all air traffic control for JFK/LAG/EWR for 10+ hours. This for a facility that is in general prepared to run on backup and does it on a regular basis. Unless you have a group that is really really set up to run on local power as your main source, it's best to use it as the backup it was designed to be. Unless the facility is ready to make a major commitment to local power generation, the risks outweigh the benefits, IMO. jerry