When discussing projects with clients we often review Total Cost of Ownership (TCO) as part of the project costs. TCO is essentially a financial accounting concept that takes into account all the costs of a system including its initial Capex (Capital Expenditure) and Opex (Operating Expenditure or Costs). Once a uninterruptible power supply is installed, the primary Opex costs are the electricity used to power the UPS system, an annual maintenance plan and any consumable replacement costs (e.g. batteries, fans, capacitors etc).
UPS system technologies have advanced greatly over the last 5-10 years with the biggest changes involving the move to transformerless designs. Not only do these types of system have smaller footprints but they are also more electrically efficient than a transformer-based UPS.
Modular design formats similar to that used in the Eaton 93PM UPS series also introduce the ability to deploy a ‘Pay As You Grow’ strategy where additional modules can be installed at a later date to meet planned (or unplanned) load expansion. The modular design also scales vertically, preserving precious datacentre or comms room floor space.
In addition to having higher on-line (double-conversion) efficiencies, UPS like the Eaton 93PM also include Eaton’s Energy Saving System. Known as ESS this is an eco-mode of operation which can further increase operating efficiency and lower the overall associated Opex-related costs – electricity consumption and cooling. A more efficient UPS system also generates less heat and reduces the burden on local air conditioning which is itself a consumer of electricity.
The table below shows a comparison of the Eaton 93PM UPS to a leading competitor system. The Eaton UPS uses an advanced triple-stage inverter design which coupled with the Eaton Energy Saving System mode can achieve an operating efficiency of 99%. Even in double-conversion on-line mode the the efficiency reaches 97% which is still very high for a three-phase UPS system.
||Leading Competitor Efficiency **
||93PM ESS Efficiency
||93PM ESS Annual Savings *
||93PM On-line Efficiency
||93PM On-line Annual Savings *
- * Savings calculated using £0.06p/kWh and 80% cooling ratio.
- ** Leading competitor UPS without ESS mode.
The table uses figures from a US-based datacentre study which we have converted to UK£. £0.06p/kWh is low compared to what most UK datacentres pay but figures would be comparable.
Another factor to take into consideration is the load range 25-100%. Typically UPS had a ‘sweet-spot’ range of 50-90% over which they reached their optimal efficiency. Modern transformerless UPS like the Eaton 93PM system can reach high efficiencies over a much wider range from 25-100% making them the ideal choice for variable loads and future load planning.
The high efficiency results of the Eaton 93PM UPS also make it eligible for the Carbon Trust UPS Energy Technology List. This means that purchasers can use their Capex investment to reduce their corporation tax bills.