Signs of the times:
Energy Benchmarking: Rich Miller at Datacenter Knowledge is reporting that TPC will update their performance benchmarks to include energy efficiency data. In the future, they’ll measure performance, price and energy in their benchmarks.
Actual datacenter energy costs (rather than power supply nameplate ratings) are hard to generalize. The numbers that I can find are all over the map. Energy use depends on server load, server configuration, server efficiency, power distribution efficiency and cooling efficiency, none of which are easily calculated and rarely measured. As a rough estimate, it looks like for small servers the cost of power + cooling approaches the cost of purchasing the server hardware and amortizing it over 4 years. Figuring energy use into the price/performance calculations for systems should skew future purchases toward efficiency.
Power Calculators: HP has a rack power calculator tool that provides useful estimates of power use for a given HP server and rack configuration. APC and others provide similar tools. I’m sure they build the tools to help figure per-rack UPS, power and cooling for custom rack configurations, but the tools can easily be used to help estimate energy costs.
Don’t forget cooling: One thing I’ve noticed is that people tend to forget that for every watt of electricity that their systems use, they’ll have more than one watt of cooling that they need to supply to remove the heat from the datacenter (or their house if they have air conditioning). The process of removing the watt of energy from the room is not 100% efficient. For example, if I have a rack that uses 5000 watts, a cooling system that was 100% efficient would use an additional 5000 watts to remove the heat from the room. But cooling systems are not 100% efficient. Worst case, you might spend up to an additional 10,000 watts of energy to cool the 5000 watt server rack.