Are you paying too much for Electricity?

Gabba Central has saved an estimated $30,000 in two months since implementing changes identified from an energy audit, with a reduction in electricity usage of around 43% overall. The energy performance index has improved substantially to approximately 12.3 MJ/m2 per month, equivalent to 147.7 MJ/m2 for a full year.

This is a building that had many complexities about it, combining residential living with commercial shops with shared common areas and separate legal entities for the residential towers and the retail lot.

The audit was requested to resolve numerous business issues with the ultimate outcome to reduce costs and the maximum demand and electricity usage of the building, thus reducing its carbon footprint.

Site Description:

Gabba Central's base building energy consumption over the 12 month period from July 2009 to June 2010 was 2,134,199 kWh or 7,677 GJ of electricity at a cost of $295,196 including GST. It is equivalent to 2,155 tonnes of greenhouse gas CO2-e or 501 cars on the road. This gave an annual energy performance index of 177.91 MJ/ m2 of gross building floor area. However some of the air handling plant was out of service for five months of this period. After allowing for this the cost for a full year was estimated at $359,000, representing an energy performance index of 244 MJ/ m2. Gabba Central has a gross building floor area of 43,154 m2 with seven levels of residential apartments across four towers and three levels of underground car parking. The car parking is designed such that there are seven split levels over three general car park areas, each being assigned to one of three basements. The tower tenancies comprise 186 apartments and several commercial tenancies of varying size covering 4250 m2 of the ground level.

One of the Business Issues: Cost allocation of common power - What energy consumption is being used in the common area? Are the costs allocated between residential bodies corporate and the retail lot fair and reasonable? To add further complexity to this question the common areas are not individually sub-metered, so there are no current measurement tools in place.

Watt Utilities was asked by the body corporate to perform a Level 2 audit, and Cypher was retained by Watt Utilities to undertake the site investigation and report. We had to identify and analyse what uses power within the building using measurement tools and then provide a series of recommendations to reduce energy usage and costs and an analysis of the energy used by the residential and the retail lots to assist in cost allocation.

The breakdown of the common area is listed in the graph below. It was apparent the car park exhaust fans were the major cost contributor to common area power at 41% of use.

Areas looked at within the Audit: We looked at all areas that consumed power and gave recommendations based on those with payback periods less than 4 years and those items with greater than 4 year pay back periods. Below are listed those with under 4 year payback period.

Savings Identified:

The energy audit identified energy efficiency cost savings worth approximately $82,000 per annum. These savings represent reduction in electricity consumption of 684,624 kWh per annum or a reduction in greenhouse gas emissions by 691 tonnes of CO2-e, equivalent to taking 160 cars off the road.

It also identified cost reduction in the electricity account for the common area with a saving of approximately $62,000 per annum or 21% at the consumption levels expected prior to implementation of the audit recommendations.

What was implemented:

Market Contract: The new contract commenced 1 January 2011 and savings of 32 % per month have already been seen in January and February compared with the rates under the old market contract.

Car park monitoring system: A system comprising carbon monoxide sensors and variable speed drives was implemented and it has not only reduced the electricity usage prior to the introduction of the new system, but it has also reduced the maximum demand. Another positive outcome is that it has reduced the noise in the car parking levels dramatically.

See below; when the monitoring system was implemented the reduction was clear.

Lighting: Gabba Central chose to implement the trial proposed in the implementation plan, replacing the current 50 watt Halogen downlights with ALTLED Aurora MR16 series 7 watt lamps as they fail. Initial reaction is that there is no discernable difference in the light output. These lamps are claimed by the manufacturer to have a life of 30,000 hours. They are direct replacements for the 50 watt Halogen lamps. If the trials are successful, savings will be greater than the estimated savings under Option s 1 or 2.

Other: Audit recommendations with payback periods longer than 4 years will be considered as funds are available. The sub-metering recommended for the common areas is still under consideration. This will provide usage sub-meters for the common areas, so that the allocation of electricity costs among the residential and retail common areas can be based on metered usage rather than agreement on calculated usage as at present.

This building not only has made significant savings as a result of the energy audit, but it has also reduced its carbon footprint.

Written by: Michael Newton Watt Utilities