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SolarPlus has been the industry-standard, best-practice design solution to meet Australian requirements since its initiation in 2012 by Solaris Pty Ltd in partnership with the Australian Solar Council.

In 2017, SolarPlus introduced an advanced performance algorithm which provides best-in-class modelling across a broad range of design configuration options including grid-connect, hybrid/backup battery storage, off-grid, system upgrades and supporting a wide range of load profile and tariff analysis options.

The 2023 v5 update uses the Cubas cell equivalent circuit model. This modern and innovative method employs an analytical approach, leveraging explicit expressions and a new mathematical technique, the Lambert W-Function, to more accurately calculate the parameters of the solar panel’s equivalent circuit. This technique enhances the precision of solar panel performance analysis to better understand and model the behaviour of solar cells under various operating conditions.

Metrics, charts, and information available from the Report Page

• Energy Summary – Generation Potential (Solar and Battery system)

• Solar generation potential by surface and monthly average (kWh/ day)

• Average Daily performance plot – that can be toggled for different dates across particular months for comprehensive analysis

• Monthly peak demand – consumption and system balancing using solar

• Monthly and annual savings summary – with and without solar for carrying out before and after solar installation analysis

• Electricity charges for peak, off-peak, and shoulder time periods

• Bill breakdown using current tariffs and incentives

• Economic Returns

  • ROI

  • Yearly Cashflows

  • Lifetime Metrics

Once the system has been designed by the user, on the SYSTEM page of the process workflow, SolarPlus, evaluates the performance of the system based on certain key parameters that have been provided by the user in the previous sections (Contact, Energy, and System pages) of the workflow. Some of them are:

• Site Location      

• Tariff rates                                        

• Consumption Profile

• Module Specifications

• Inverter Specifications                 

• Battery Specifications

Utilizing the above-mentioned input parameters, supplied by the user at various stages of the workflow, SolarPlus computes the performance of the renewable energy system as a whole. Performance metrics toggled for various energy systems (solar, battery) would be toggled as they are being designed as part of the quotation.

Solar and battery performance would be calculated and compared across different time frames and different seasons, to help the users actively visualize the system’s capabilities towards meeting and adequately balancing the energy demands of the location at any given site.

When looking at this chart, it is recommended that users set the time range to week view and check the chart for different months (for example, January to check summer performance and June to check winter performance). Drilling down to the weekly views of different months can help users check the system performance including battery charge/discharge cycles across the specified week.

Exporting Data

You can export the data in any of the charts on the Reports page in various formats.

Some of the Reporting Metrics Explained:

SolarPlus offers a wide range of metrics to illustrate system performance in energy and financial units, often comparing the situation before with that after the proposed system installation. This page explains the assumptions and calculation methods for these metrics.

Commercial Metrics

1. Cashflow Breakdown Table

This table for commercial systems gives an estimate of cashflow credits and debits broken down into categories for each year in the system lifetime.

1. Subsidy

The Subsidy column in the cashflow table includes STCs if applied in year one, or if LGCs are applied, these will be added in year two until the year 2030. See the LGC calculation method below.

1. Export Earnings

Export earnings are based on solar (and possibly storage) export multiplied by the solar-feed-in tariff set (which may differ per tariff time-of-use period). NO annual escalation rate is applied.

1. Sales Tax

This has been removed from the commercial cashflow tables as no sales tax is being applied in any of the ROI figures or charts for commercial proposals.

1. Tax Effective Depreciation

Depreciation defaults to the Australian simple depreciation method. The asset value is the system cost less STC/LGCs. In year one the asset is depreciated by 15% and in subsequent years by 30% with a nominal tax rate of 30%. No depreciation is applied after year 20.

Depreciation can be customised for any commercial quote on the Pricing > Financials page. You can enter the first-year value as either a percentage or a dollar amount, add a subsequent year depreciation rate and add a tax rate.

1. Bill Charges

The Bill Charges column shows the estimated annual electricity charges including all fees and charges (as per the annual bill comparison chart) excluding sales tax, and with the annual tariff escalation rate applied.

1. Cost of Finance

The Cost of Finance column will include any finance repayments including principal and interest charges.

1. Capital and Maintenance

The Capital and Maintenance column includes the purchase price, annual maintenance allowance and up to two reinvestment amounts for system upgrades.

1. Tax Debit

Commercial enterprises can expect to have income tax applied on export earnings as well as on incentives.

10. Net Cash

The Net Cash figure is the estimated total annual cost including all Cash Incoming and Cash Outgoing amounts.

11. Comparison Cost

The Comparison Cost is the estimated annual cost of electricity based on the historic consumption (or estimated load profile) and applying the tariff escalation rate annually.

12. Accumulated Savings

The Accumulated Savings figure is the Comparison Cost less the Net Cash value, providing an estimate for the total accumulated savings throughout the system lifetime for the cashflow simulation.

13. LGCs (Australia)

For information on applying LGCs, please refer to: https://solarplus.atlassian.net/wiki/spaces/SPHC/pages/1270841381/5.+Pricing+Page+-+SolarPlus#LGCs-(Australia)

14. Carbon Emissions CO₂ Reduction Calculation

After a tally of grid kWh reduction is tallied over the lifetime of the system, factoring panel degradation, this is multiplied by a carbon emissions multiplier provided for each state (published by Dept of Industry, Science, Energy & Resources) and divided by the lifetime in years for the average value. See Australia’s emissions projections factors for the electricity grid as used in calculation of emissions reduction (updated 2024)

For NZ - the rate is 0.131 kg CO₂/kWh * kWh grid reduction averaged over the lifetime of the system. (The lifetime value is on the basis of grid reductions i.e. solar consumption and solar export will be considered as reducing grid supplies, potential PV production that is curtailed due to export limits will not.)

There are various reports tags for CO2 emissions reduction equivalent:

Annual average grid avoided emissions [[carbon_reduction]] (based on solar utilised)

Lifetime total grid avoided emissions [[carbon_reduction_annual]] (based on solar utilised)

Car emissions equivalent is based on 4.62 tonnes per year per car (Source: EPA)

Tree emissions credit is based on 0.0614 tonnes per tree per year (Source: EPA)

15. Internal Rate of Return (IRR)

The internal rate of return is a value at which the Net Present Value (the present-day value of all future savings) is reduced to $0. That is, the Net Present Value is set to zero and we solve for the discount rate at which this happens.

Factors: Annual savings on a cash sale basis (residential sales include GST, commercial sales RoI excludes GST and may include LGCs (AU)); Optional, for commercial quotes users can select to include Depreciation on the basis set in Pricing > Financials and this will be included in all-cash basis return on investment metrics including IRR. (Proposal tag: [[system_roi_irr]] )

NOTE: PENDING RELEASE For financed systems there is a separate IRR calculation and value tag [[system_roi_irr_fin]] that can be included in proposals. In this case, the basis of the savings for each year becomes the estimated cost of grid power (escalated based on the tariff escalation rate) less the cashflow after value. Both of these lifetime costing series can be seen presented in the Finance Cashflow Table.

16. Net Present Value

The Net Present Value is the difference between the present value of the net cash inflows and the present value of the net cash outflows over the period of the system lifetime as determined by the user.

Net cash inflows includes: earnings on exported energy, nominal savings from avoided grid cost including the value of estimated tariff escalation rate, and nominal savings from avoided generator costs.

Net cash outflows includes: Initial purchase investment, any subsequent reinvestment in the system, maintenance costs, and supplementary grid or generator costs.

Module degradation rates (year 2 and subsequent years) are factored into all future year energy and savings analysis.

Residential vs Commercial: Annual savings on a cash sale basis (residential sales include GST, commercial sales RoI excludes GST and may include subsidies).

Optional, for commercial quotes users can select to include Depreciation on the basis set in Pricing > Financials and this will be included in all-cash basis return on investment metrics including Net Present Value.

17. Tax Implications and Tax Treatments

The three main areas of consideration for commercial solar finance and return on investment are:

• Sales tax

• Income tax

• Depreciation

Sales tax

• Sales tax may apply to the system price and this will be stated on the quote and invoice, although in different ways for residential and commercial customers.

• In terms of return on investment for commercial systems, all investment factors are considered exclusive of sales tax.

• In commercial systems, sales tax may apply to subsidies (AU: eg. STCs or LGCs).

• For residential customers only, sales tax in terms of RoI will factor the tax in bill totals, before and after the system installation.

Income Tax

• Any feed-in tariff is treated as assessable income and therefore a tax debit applies for any year where feed-in tariffs are considered.

• AU: The ATO treat Renewable Energy Certificates as “assessable recoupments” and therefore subject to income tax. This may apply in the first year in the case of STCs or in subsequent years in the case of LGCs.

• A tax debit applies for these liabilities based on the tax rate set at Pricing > ‘Financials’.

Tax-effective depreciation

• Depreciation handling can be controlled in the Pricing > Financial page for any client-marked commercial.

• You can set a first-year depreciation method as either a dollar value vs a percentage value and enter the value that is applicable. You can set a percentage value in the third field for the depreciation percentage in subsequent years.

• Depreciation will be shown on the commercial detail proposals under Cashflow Table > cash incoming > tax-effective depreciation

• Depreciation is calculated over a 20 year period

  SolarPlus also houses special features that help users attach brochures for modules and inverters, as part of the proposal in PDF format.  

18. Estimated year 1 savings. The entire modelled electricity bill of the before scenario, minus the modelled bill of the proposed scenario.

Commercial is ex. GST and includes depreciation (if selected in Pricing > Financials).

Weather and Irradiance Data

SolarPlus sources reliable weather and irradiance data from the world leader in this field, Meteonorm, which was initiated by the Swiss Federal Office of Energy in 1985. Meteonorm has developed a global climate database based on ground measurements and satellite weather data at an 8km resolution, with over 20 years of recorded data.

State-of-the-art interpolation models combine this data to build a typical meteorological year - individual days retain the variability of actual day data, while the overall month to month is biased to reflect the average year.

Using typical meteorological year data is by far more accurate than using monthly average data, or indeed the recorded data of a specific year which, if repeated, would not be representative of the weather at that site over the system lifetime as it does not account for variations which occur from one year to the next. However, one limitation of typical meteorological year data is that while it does show multiple consecutive days of low insolation, these may not be consistent with extended rain events experienced in particular years due to La Nina or other long-cycle weather patterns. In the case of off-grid power systems, this means that the generator run-time and battery hours of autonomy calculations do not account for the absolute worst case scenario, so we encourage designers to use common sense when sizing off-grid power systems to take this into account.

Solar Performance Simulation

SolarPlus performs an analysis of solar power generation using a module-level simulation that generates the expected module output for any orientation at each hour of the year (8760 hours). The components of direct, diffuse and ground-reflected radiation data from the sun are derated using the Perez model, and factoring shading, glass reflectance, and soiling to arrive at the irradiance impinging on the panel front, and if a bifacial module, adjusted for on the rear surface. Adjustments for temperature and wind for each hour, and accounting for proximity to the mounting surface, provide the derating of the cell according to its manufacturers specifications.

SolarPlus features an advanced single diode cell equivalent circuit model, that is to say the cell circuit performance is simulated using the datasheet Isc, Imp, Voc & Vmp values, and using the temperature coefficients adjusted to the temperature conditions in each hourly interval in which the output is calculated. The model arrives at the five parameters used to determine the module output at the given irradiance: Light current, reverse saturation current, series resistance, shunt resistance and diode ideality factor.

According to the system electrical configuration, module and string voltages and current are modelled with allowance for the variability due to module mismatch, manufacturing tolerances, and cabling losses at each stage of the power transmission. Inverter losses due to tracker and output stage current and power limiting are calculated and inverter efficiency and AC derating factored into the usable energy potential to the site switchboard.

Energy and Savings Simulation

SolarPlus supports energy simulation down to 10 minute resolution in order to simulate performance of battery storage systems, consumption power flows, grid interaction and, for off-grid systems, generator runtime.

Battery system performance is modelled according to the specifications of the manufacturing and factoring roundtrip efficiency, configuration set-point limits, depth of discharge limits, and accounting for battery chemistry characteristics.

Grid interactivity levels are controlled with export limits, set-points for any battery grid charge or battery export and all energy flows accounted according to the electricity tariff structure set for the site including time-of-use, tiered tariffs and demand charge rate.

Lifetime Return on Investment

SolarPlus conducts an assessment of potential payback on investment factoring solar panel degradation, tariff escalation rates, reinvestment amounts in future years, maintenance costs.

More detailed return on investment analysis of lifetime savings can be generated including depreciation, costs of finance, subsidies. Discount rates are applied to estimate an Internal Rate of Return and Net Present Values of the system over the lifetime period.

Carbon emissions reduction is calculated based on grid energy reductions using the state emissions reduction coefficient (CO2e per kWh) published by the government of the relevant territory. Where government figures are unavailable, reputable third-party sources are used.

De-rating Table

SolarPlus provides a report