Solar PV & battery financial analysis calculator


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Are you considering installing batteries to make better use of solar power?  NSW Farmers has developed a calculator to assist agribusiness enterprises in evaluating batteries as part of solar generation solutions.  Battery storage is criticial to the viability of solar for many agricultural electricity loads such as irrigation pumping, or feed preparation, which may occur outside of daylight hours. 

The calculator is  designed to help small and medium enterprises and residential consumers better determine the potential savings and financial case for installing a grid-connected solar PV system and/or a grid-connected battery (such as the new Tesla Powerwall on offer from Origin Energy or NaturalSolar, or the various battery offers available from AGL and Redflow). 

How does the tool work work?

The calculator helps you to model an average work day and an average weekend day based on inputted parameters. Consumption (and solar resource) during these days is then calculated in 15-minute intervals and multiplied accordingly to ascertain consumption over an average week. This average week's consumption is then multiplied by 52.14 to derive an average yearly total.

Enter the parameters required by the calculator (the cells in white) to enable you to calculate the financials of your selected scenario.

If you would like to know about the detailed workings of this calculator and developments in energy storage and solar PV, click on the video below to watch a webinar addressing this and more. An explanation of the calculator begins at the 29m:50s mark (click on this link to access the video at that point).




Any advice, data, results, or any type of information or message that is derived or can be derived from the use of this tool has been provided for your convenience. NSW Farmers makes no warranties about its accuracy or completeness, and accepts no liability for any losses or damages that may result from its use.

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More information

Baseline consumption

Enter the average kWh consumed on a typical weekday and weekend day, and select the profiles that you believe best fit your typical consumption for each type of day respectively. If you already have a PV system, enter the kWh consumed and the profile you would be likely to experience if you did not have one.

Pricing and electricity tariff structure details

The calculator is pre-populated with tariff structures, schedules and prices from the leading electricity retailers in NSW. In order for the calculator to work, you must select the distribution area (you can find your local distributor using this map or by using your postcode via the following link:, retailer and tariff structure that best apply to you. You may also adjust the discount that applies to your contract (only on consumption charges) or choose to input your own custom prices by selecting 'Yes' in the 'Use custom prices?' field.

Solar PV system details

  1. If you already have a solar PV system, enter its size (in kW) in the designated cell. If you do not yet have a solar PV system installed, enter the size of the system you are considering.
  2. From the dropdown menu, select the city closest to your location; this will be used to model the available solar resource on your property.
  3. If you know the cost of the solar PV system you have or are considering, enter it in the designated cell. If you do not know the cost, select 'don't know' - the calculator will then use an in-built algorithm do determine the cost of the system using average prices per watt for the applicable system size, derived from recent quoted prices as published by the quote aggregator SolarChoice

Other notes:

  • The tool considers any solar PV system to yield the output that would be generated by a system of the designated size, with no obstructions, facing north, pitched at 30 degrees and installed in the selected location.
  • PV derating losses of 20 percent as well as as minor temperature effects have been incorporated into the tool. The PV output is considered to be the average output over a year from the inverter, as given by analysis and modelling of a 1kW system using the software HOMER. This output is scaled linearly from 1kW to the sizing parameter (in kW) set in the tool.

Battery details

Use the dropdown menu to select one of the pre-populated parameters and pricing for one of the several residential battery systems currently available in Australia. These include:

  • The Tesla PowerWall, as offered and priced by Origin Energy, NaturalSolar and CSR Bradford from December 2015;
  • Redflow's Zinc Bromide ZBM2; and
  • AGL's Powerlegato and SunVerge battery systems.

Or select 'Custom' from the dropdown to enter the relevant parameters for a battery of your own choosing.

If you do not wish to consider a battery, simply ignore this section.

Important battery limitations
  • The tool does not model Peukert's law (i.e. the change in capacity of the battery at different rates of discharge); hence, it is not suited to model lead-acid batteries or any batteries that display the influence of Peukert's law significantly.
  • The tool uses a single de-rating factor to account for capacity degradation of the battery's use over the analysis period. The method for arriving at this factor is explained in the following post: Battery capacity degradation in the Solar + Battery Financial Analysis Calculator

New consumption: scenario selection

The tool allows you to model the following types of scenario:

  1. The financial case for doing nothing: 'Nothing (Baseline - No battery, no PV)'.
  2. The financial case for installing a solar PV system: 'Just new PV'. Choose this scenario if you are not planning to install a battery in the immediate future and just wish to know the financial outcomes of installing a solar PV system.
  3. The financial case for installing a new solar PV system combined with a new battery system: 'New PV and new battery'. Select this option if you do not have a solar PV system and plan to install a new one, along with an integrated battery.
  4. The financial case for installing a new battery when you already have a solar PV system: 'Just new battery with existing PV'. Choose this scenario if you already have a PV system and want to investigate the cost of and potential savings that would result from adding a new battery to this system.

Yearly savings and financial case analysis

The final section of this calculator tool provides you with a summary of the performance you could expect from the scenario you selected on the basis of financials. You can change the expected annual electricity cost escalation (i.e. how much you expect power prices to rise every year), the discount rate (this can be interpreted as your minimum desired rate of return) and the number of years over which you want to consider the project. For scenarios involving a battery, we recommend that you select a time frame of 10 years (as few solar battery warranties and cycle lifes extend beyond a decade). For scenarios that include solar PV only, we recommend using '14-20 years' as the analysis period, since PV panels usually have long lifetimes (typically, of 20 years+); however, inverters typically fail or are out of warranty by around the 14-year mark.

NPV stands for 'Net Present Value'.

IRR stands for 'Internal Rate of Return'.

The amortised cost of power describes the total expense of providing electricity to the designated dwelling over the selected number of years (and includes the cost of investments, as outlined in the selected scenario) divided by the total kWh provided.

Note: Since this calculator tool uses a repeating load for every work day and weekend day, as well as a repeating solar resource profile for every day of the year, it is not suited to modelling or analysing outcomes for residences or businesses that typically experience significant seasonal or yearly variations in consumption. For instance, if your business uses a lot of electricity over a few months of the year but virtually none at other times, this calculator tool will not be suitable for you.

However, for a fee (typically $400), NSW Farmers' Energy Information team can conduct more sophisticated modelling that takes seasonal variations in consumption into account.

For more information and/or to arrange a customised analysis, contact NSW Farmers' Energy team on 02 9478 1004 or email us at

Other important notes and limitations

  • The model averages seasonal variations as opposed to modelling output and loads for each season, month or individual day. This has the effect of underestimating the solar power available in summer and overestimating that available during winter.
  • Consumption profiles have been selected from a variety of sources but may not reflect your particular pattern of consumption. The selected profiles are modelled to repeat the typical consumption patterns entered for week and weekend days for every workday and weekend day of the year. This is a significant simplification and is the largest source of inaccuracy in the tool. Please note that the tool can provide only an approximation of what may occur over the modelled period, and is prone to some inaccuracy in its results.
  • Depth of discharge (DOD) is considered but not modelled in the tool. If using a custom battery, make sure you input the kWh capacity of the battery that is available (after considering depth-of-discharge limitations), not the total.
  • This tool does not model Peukert's law (i.e. the change in capacity of the battery at different rates of discharge), so it is not suited to model lead-acid batteries or any other battery types that display the influence of Peukert's law significantly.
  • The calculator conducts a preliminary assessment to determine the likley charge level on the beginning of the week (Monday). The calculated value may or may not be accurate. 
  • Batteries typically experience a loss in their capacity to store energy (charge) over their cycle life. This degradation over time has been modelled and acounted for via a single de-rating factor. This factor is influenced by the following inputted parameters:
    • 'Capacity retention at the end of cycle-life';
    • the 'Cycle life' of the battery;
    • the length of the analysis (in years); and
    • a preliminary assessment that estimates the number of cycles that the battery will endure every year.
    • More information on how this degradation factor is calculated is available in the following post: Battery capacity degradation in the Solar + Battery Financial Analysis Calculator.
  • The tool incorporates residential tariff structures only, not demand or kVA charges.
  • The tool assumes that any discount to the tariff pricing will apply only to consumption charges and not to supply charges or PV exports.

Change Log

30 March 2016

  • Removed Redflow's ZBM2 and added Redflow's ZCell battery

22 March 2016

  • Updated PV pricing to March 2016
  • Added LG Chem RESU battery

17 March 2016

  • Updated capacity retention at end of life for several batteries 

23 February 2016

  • New algorithm to estimate price of a solar PV system.
  • New algorithim predicts starting charge state of battery at the start of week (Monday). It no longer defaults to zero.  
  • 'Battery degradation' derating now incorporated.
  • New consumption profiles added (sunwiz), redundant ones removed.
  • More information displayed on baseline and upgraded consumption (yearly bills, portion of consumption that falls during peak, off-peak and shoulder times)
  • Fixed spelling of 'electricity'.

© NSW Farmers

See also: Batteries are good news, but are they suitable for you?

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Farm Energy Innovation Program (EEIG)