Energy Savers
Southern Downs

Southern Downs Piggery

Energy Savings
Solar Photovoltaic
Capital Cost


An energy audit at a Southern Downs piggery investigated electricity and gas consumption and has identified opportunities to significantly reduce costs. The piggery has saved money and reduced energy consumption after implementing a 39.36 kW solar PV system.

Electricity Audit

The site farrows and weans pigs before transporting them to a larger site for finishing. The site has several sheds for different stages of rearing, two houses, a small office, and two pumps.

The farm could save electricity onsite from recommendations in the audit:

  • Upgrade lighting using new LEDs, which is the quickest way to improve efficiency on-site with a payback period of less than a year.
  • Upgrade Ventilation fans.
  • Reflective roof coating.
  • Solar Bore pump with or without battery storage.
  • Various solar PV systems up to 100kW in size.

Table 1. Costs and savings from audit recommendations with quick payback.

Recommendation Energy Saving (kWh) Cost Saving Tariff 62 ($) Cost Saving Tariff 20 ($) Payback Period Tariff 62 (Years) Payback Period Tariff 20 (Years)
Upgrade lighting to new LEDs 26,280 10,990 8,300 0.5 0.9
Fan Upgrades 14,400 4,200 3,700 9.5 10.8
Reflective roof coating 7,500 3,000 1,800 >20 >20
Total 48,180 18,190 13,800 N/A N/A


Under current tariff 62, the annual cost savings of $10,990 from the replacement of the lights could be utilised to install an adequate solar PV system.

The audit also considered a number of solar energy opportunities with relatively quick paybacks, including:

  1. Two smaller residential solar systems 1.5kW and 5kW.
  2. Bore Pump: Solar only or Solar and batteries.
  3. Large scale solar PV systems of 30kW or 99.5kW.

Table 2. Costs and savings from audit recommendations with longer payback.

Recommendation Energy Savings (kWh) Cost Savings Tariff 62 ($) Cost Savings Tariff 20 ($) Payback Tariff 62 (Years) Payback Period Tarif 20 (Years)
Two Residential Solar Systems 7,930 3,700 2,300 2.4 3.8
Bore Pump: Solar only (Tariff 33) 10,900 1,600 N/A 4 N/A
Bore Pump: Solar and batteries (Tariff 33) 13,000 1,900 N/A 11 N/A
30kW Solar PV 43,000 14,500 9,000 2.9 4.3
99.5kW Solar PV 62,000 19,600 11,400 4.9 9.4


Assuming the bore pump is on load control tariff 33, an initial solar system is recommended to cover the load with this showing a four-year payback. Should battery pricing decrease, then the second option may be worth considering. It would be worthwhile to factor this when designing a system using a battery-capable invertor.

Solar systems greater than 30kW are subject to a more complex network connection process, so the installation of the 30kW system would prove beneficial at this stage. The audit recommended remaining on tariff 62 as the system shows better payback. The farm will be required to move to Tariff 20 when the obsolete tariffs cease.

Table 3. Costs and savings from preferred audit recommendations.

Location Current Usage (kWh) Current Cost ($) Recommendation Energy Saving (kWh) Cost Savings ($) Capital Cost ($)
Piggery 115,272 36,607 Lighting and
30kW Solar PV
Main Bore Pump 10,385 2,001 Solar system only 10,900 1,600 10,000
Farmhouse 15,435 5,408 Solar PV 7,900 3,700 8,100
Total 141,091 44,016 N/A 88,080 25,300 36,100


Implementation of the recommendations at the piggery will ensure that the farm is able to remain a small electricity user on small business tariffs.

The farmer has proceeded with the installation of a 39.36 kW ground-mounted solar system with 2 x 15 kW inverters. The energy and cost savings made have been measured in a Measurement and Verification (M&V) process, as outlined in Table 4.

Table 4. Estimated and Actual energy and cost savings.

Metric Audit estimation M&V calculation Variation (%)
Energy Savings (kWh) 43,000 76,282 77
Cost Savings ($) 9,000 14,692 63


The greater savings obtained from the M&V calculations compared to those estimated in the audit may have been influenced by the larger system implemented. No additional factors have been identified, such as higher solar radiation during the measurement period or optimization of the orientation of the panels.

From the solar generation, 74% or 56,489 kWh are being used onsite valued at $13,136 and 19,793 kWh are being exported to the grid with a revenue of $1,556. Considering that 59,743 kWh – 51% of the total energy use onsite – are being imported from the grid at a cost of $13,893, there are additional potential savings from shifting consumption into the solar generation period.

The next step for the farm is to adjust energy usage to offset as much energy consumption as possible from the grid, which would lead to further cost savings. The revenue from feeding into the grid is lower than the cost savings from using the energy onsite: for every dollar of energy exported, more than $3 could be saved if the energy were consumed onsite.  If the farm were to shift 19,793kWh of energy consumption per year to coincide with solar generation times, they would save an extra $3,047 per year.

From the implementation of the recommendation in the audit, the farm has reduced total energy consumption by 54% and cost savings by 33%, including feed-in revenue, with Carbon emission savings of 61.8 t/CO2-e per year.

Table 5. Pre and post implementation energy consumption, costs and energy productivity improvements.

Metric Pre-implementation  Post-implementation Reduction (%)
Energy Consumption (kWh) 141,091 64,809 54
Cost  ($) 44,016 29,324 33
Energy Productivity (kWh/pig) 6.56 3.0 54

Gas Audit

The audit identified a number of cost-effective initiatives onsite that could reduce gas consumption by 1,083GJ per annum with emission savings of 56 tCO2-e, including the items in the table below:

Table 1. Costs and savings from audit recommendations.

Recommendation Energy Saving (GJ) Cost Savings ($) Payback (Years) Capital Cost ($)
Solar Hot Water (Farrowing Shed) 590 24,500 3.1 3,000
Temperature Control for Heat Mats 415 18,500 0.4 7,000
Insulation on Hot Water pipes 78 3,500 0.8 1,600
Total 1,083 46,500 1.4 11,600
Biogas system 1,680 67,000 5.3 400,000


The audit considered the opportunity to install a biogas facility capturing and recycling gas produced from the piggery. This would reduce the high costs attributed to LPG, though due to production numbers, biogas production is limited and is not recommended unless the piggery expands into the future. At a cost of $400,000 and a potential payback of 5.3 years, the biogas is more a long-term consideration depending on the future direction of the farm.

Implementation of all the recommendations from the audit would significantly reduce LPG gas consumption and costs per unit of output by 52%, with new KPIs seen. Should the farm capture and use biogas then a further 28% reduction in LPG may be achieved.

Table 2. Pre and post audit gas and productivity savings.

Pre-Audit 21,510 2,102 0.097
Post Audit 21,510 1,019 0.047
Post Audit with Biogas 21,510 422 0.019


The farmer has not proceeded with any of the gas-saving recommendations. However, in the measurement and verification process, an alternative solution to save gas was identified and recommended for future implementation. The installation of an electric heat pump to replace the current water heating system consisting of 4 heaters of 275 L, could lead to a reduction of $5.12 per hour per heater at a capital cost of $43,000.

With LPG costs considerably larger than electricity, the farm should consider low-cost recommendations to allow additional capital expenditure to implement some of the larger energy-saving measures. There are significant electricity savings to be realised onsite leading to reduced KPIs.

An energy audit is a good investment 

An energy audit is a great way for a business to cut costs and boost productivity. Find out about what’s involved in an energy audit HERE and subscribe to our bi-monthly energy e-news HERE.

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The Energy Savers Plus Extension Program is delivered by the Queensland Farmers Federation with support and funding from the Queensland Department of Energy and Public Works.