Run the numbers
Field Calculators
Fast field calculators that work in your browser. Formulae and assumptions are shown, with AS/NZS context where a standard applies. No sign-up required; saving is optional.
System design
Size the array, record roof direction and check the inverter relationship.
Sizing Tool
Solar System Size Calculator
Turn your daily energy use, location-specific sun hours and entered system losses into an indicative array size and panel count.
Array kW · panel count · effective sun input
- NEM12 Load ProfileDaily kWh · window kWh · interval-average peak kW · hourly shape · export
- Power DensityW/m² · module efficiency · panels per kW
- Tilt & OrientationDirection · entered pitch · generation timing
- Near-Shade CheckSun-path chart · months and times behind each obstruction · row spacing shade-free for your window
- CompatibilityString voltage · voltage headroom · current check
- MPPT AllocationCold Voc · Vmp window · summed Imp and Isc · DC:AC ratio
- Equipment StatusCEC list, delisting and product recall links · CSIP-AUS evidence · Western Power sources for WA · manufacturer firmware pages · dated check line
- Owner Handover CardOne A4 page · verbatim codes · reviewed owner actions · blank write-in lines
- DC:AC RatioDC:AC ratio · entered capacity relationship
Strings, cables and grid
Work through string limits, conductor sizing, voltage and supply identification.
Engineering Tool
Solar Cable Voltage Drop Calculator
Work out voltage drop on a DC string or single-phase AC run from the entered length, current, conductor size, voltage and material.
Voltage drop (V) · drop % · disclosed inputs
- Phase CheckerLikely supply · visible clue · safety check
- Phase BalanceAverage current · phase spread · highest phase
- Supply HeadroomPer-phase current · headroom in A (arithmetic) · spread-minimising phase allocation
- Voltage RiseVoltage rise · rise percentage · recorded headroom
- Rise BudgetEstimated rise per segment · total rise · largest contributor
- Cable SizingMinimum mm² · next listed size · actual drop %
- Loop Impedance ExpectationExpected R1+R2, R2 and Zs (arithmetic) · difference from your reading · causes to check
- String SizingMin/max modules per string · cold Voc · voltage headroom
- String TestsExpected Voc · sibling spread · consistent or review per string
- Output Spot CheckClear-sky ceiling · the working · above it, below your threshold or can't judge
- Grid Profile SettingsMenu or app path · profile names as printed · network settings pages · region in the network's words · dated settings line
- AC Protection SheetRCD statement · upstream breaker rating and how it is framed · AC conductor range · document, revision, page and SHA-256
Batteries, rebates and financials
Explore storage capacity, backup runtime, incentives and project economics.
Battery Tool
Battery Backup Runtime Calculator
Estimate how long a battery can support a nominated essential load from usable capacity, backup reserve and conversion efficiency.
Available kWh · estimated runtime · supported load check
- PaybackAnnual savings · payback years · 10 & 25-year net
- Battery SizeUsable kWh · nominal kWh · nightly load covered
- Charge TimeEnergy required · input energy · indicative charge time
- Essential LoadsContinuous kW · daily kWh · starting demand against the entered surge rating
- STC EstimateSTC count · entered gross value
- Battery IncentivesBattery STCs · tier breakdown · conditional WA amount
- End-of-Life & ReturnsAgency pages by state · stewardship status in the page's words · ADG Code · manufacturer return pages · dated link check
About the tools
Using the calculators
- Where do the calculations happen?
- Entirely in your browser. The tools require no email or sign-up. Nothing is sent to Wattbench unless you sign in and deliberately save a result.
- Are the results a formal quote?
- No. Every calculator gives an estimate to help you reason about a system, not a quote or an engineering specification, and shows the formula it uses so you can check the working. The Equipment Status Check gives no estimate at all: it links to the live authority pages so you can check an exact model yourself. The Owner Handover Card gives none either: it prints the fault libraries' reviewed owner actions for the system owner. Nor does the End-of-Life & Battery Return Pathway: it links the agency, stewardship, transport-code and manufacturer pages for removal and return jobs. The Grid Profile Settings Finder gives none either: it links each network's settings page and each inverter family's menu path and profile names. Nor does the Inverter AC Protection Sheet: it records what each manufacturer's manual states on the RCD, upstream breaker and AC conductor range, with the page.
- Do the tools cost anything?
- No. Every tool is free to use with no sign-up. Saving a result to an account is optional. Where a formula or worksheet has been reviewed, its page carries that specific review date.