I can name a half-dozen utilities that continue to struggle with data center market assessments. That's a broad term, but one key element is determining the existing load that data centers represent in a given utility service area.
There is no question that making a qualified estimate can be done if a utility is willing to accept some reasonable uncertainty, and I will describe how I'd go about it in broad terms later. But one key element is to find the "known knowns" of the market - the large, stand-alone facilities that utilities can cull straight from an analysis of their customer records.
These facilities are "utility scale" in that they are all pulling loads of say five or more megawatts, and they are almost always self-contained rather than part of some other facility like a high rise office building, office park, or other campus.
There are three primary submarkets to look for: owner-operators, wholesale colocation facilities, and retail colo operators.
The owner-operators are the Googles, Amazons, and Microsofts, along with some financial and governmental institutions. The wholesale colos are Digital Realty Trust, Dupont Fabros, and others.
Lastly there are the retail colos, lead by Equinix and Savvis (now Century Link).
The difficult part about the colo market is that it is very fragmented - one vendor focused on this market segment said they had a list of 800 companies in the market, which means that there must be several thousand facilities out there.
This market analysis of the retail colo sector by Synergy Research Group, reported by Data Center Dynamics, gives a great snapshot. And although seven operators make up half of the market, it's pretty clear that there is still a lot of fragmentation.
Nevertheless, if I wanted to estimate data center load in a given region, one place to start for a utility is to run a search for the big names in the utility-scale segment, including the "big nine" retail colo operators noted in this report.