Solar payback time: assumptions and descriptions

ATA Model Assumptions (Updated March 2013):System size: 2.0 kW

  • System cost (fully installed, before payment for STCs): $4,400
  • STC price: $30
  • Electricity export rate:
    • For net feed-in tariff jurisdictions (i.e. QLD, SA, NSW, Victoria and WA), ATA modelled two scenarios where a household exports 30% or 50% of the total electricity generation from their solar PV system into the grid.
    • For gross feed-in tariff jurisdictions (i.e. Tasmania, NT and ACT), ATA modelled 100% export of the total electricity generation from their solar PV system into the grid.
  • The following Zones were used for the purpose of STC calculation:
    • NT: Zone 1 (Alice Springs)
    • QLD: Zones 1 – 3
    • SA: Zone 3
    • Tasmania: Zone 4
    • Victoria: Zone 4
    • WA: Zone 3 (Perth)
    • NSW: Zone 3 (Sydney)
    • ACT: Zone 3
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    System degradation rate: 0.5% per annum

  • Value of feed-in tariff: See table below
    • NSW – The NSW feed-in tariff is no longer regulated and ATA has used the higher value of 8 c/kWh, currently offered by some retailers.
    • WA – The modelling uses the Synergy network feed-in tariff rate and does not take into account the higher feed-in tariffs available in the Horizon Power network for certain towns and remote locations.
    • ACT / Tas – These states currently offer a feed-in rate to match the rate paid for electricity purchased from the grid (i.e. 25c / kWh).
  • Value of electricity consumption purchased from the grid: 25 c/kWh
  • Inverter is replaced after 15 years at a cost of $800
  • Annual increase in retail electricity price: 0.25% (equivalent to 6.4% increase over 25 years)
    • This value is based on the forecasts for eastern states by the Australian Energy Market Operator (AEMO) in the report “ECONOMIC OUTLOOK INFORMATION PAPER – National Electricity Forecasting 2012”.
  • Discount rate: 5%
  • Ranges in payback for some locations (e.g. 8-10 years) is due to the range of STC zones within that state.
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