One can write about this at length. A few points:

Atomic servers - easy to update, easy to build redundancy, easy to back up and to upgrade, fast (real time display of meter data in web pages where relevant)

Vertical distribution - in line with Atomic servers: means that you can scale infinitely, there are no bottlenecks in the architecture.

Thin client - Web browser. Means your users can be anywhere

Pure HTML (no ActiveX, Applets or Silverlight etc, so this can run in e.g. a Bank or other secure facility - supported by all browsers)

Free O/S (Linux), Free DB (PostgreSQL), Free libraries - no license problems, maximum technical and commercial flexibility

Internationalization of currency and timezone, on the same server.

for

Flexibility

Scalability

Simplicity

Performance