Solar Panels kWh Calculator

Free solar panels kWh calculator for Australia. Enter your monthly kWh use, target offset, and panel wattage to see system size, panel count, and bill savings — calibrated to BoM and Clean Energy Council standards.

Solar Panels kWh Calculator

Monthly electricity use (kWh) Target offset (%) Peak sun hours/day System efficiency (%) Panel wattage (W) Electricity rate (A$/kWh)

System size needed

4.84 kW

Panels needed

Offset achieved

95.3%

Daily production

16.99 kWh

Monthly production

516 kWh

Annual production

6,201 kWh

Year-1 bill savings

$2,108

How to use this calculator

This tool sizes a solar system from the kWh number on your electricity bill — the opposite direction of a production calculator. Enter six values and it returns required system size in kW, panel count, daily/monthly/annual production, offset achieved, and year-1 bill savings:

Monthly electricity use (kWh) — average from your last 12 months of bills. AER’s 2026 average is 542 kWh/month (6,500 kWh/year).
Target offset (%) — how much of your bill you want to eliminate. 90% is standard without a battery; 110%+ if you have storage.
Peak sun hours per day — Australian average is 4.5. BoM Solar Resource Maps show exact values: Darwin 5.7, Brisbane 4.9, Perth 5.4, Sydney 4.4, Melbourne 4.0, Hobart 3.6, Adelaide 4.7.
System efficiency (%) — leave at 78%. CEC Design Guidelines default for Australian rooftop installations.
Panel wattage (W) — STC nameplate. 2026 Australian standard is 440–510 W (Q CELLS Q.PEAK DUO ML-G11+, Jinko Tiger Neo, REC Alpha Pure-RX).
Electricity rate (A$/kWh) — your blended residential retail rate. AER DMO 2025-26 averages 33–36c/kWh; flat tariff varies by state and time of use.

The formula

annual_need_kWh   = monthly_kWh × 12
target_kWh        = annual_need_kWh × (offset / 100)
required_array_W  = target_kWh × 1000 / (PSH × 365 × derate)
panel_count       = ceil(required_array_W / panel_W)
actual_array_W    = panel_count × panel_W
daily_production  = actual_array_W × PSH × derate / 1000
year1_savings     = min(annual_production, annual_need) × rate

The savings figure assumes self-consumption — exported kWh earn the FiT, which is much lower than retail. The savings calculator handles the dual-stream model.

A worked example for the AER average household at 90% offset:

Need: 542 × 12 = 6,504 kWh per year
Target: 6,504 × 0.90 = 5,854 kWh
Required array: 5,854 × 1000 / (4.5 × 365 × 0.78) = 4,575 W
Panel count: ceil(4575 / 440) = 11 panels
Actual array: 11 × 440 = 4,840 W (4.84 kW)
Daily production: 4840 × 4.5 × 0.78 / 1000 = 17.0 kWh
Annual production: 17.0 × 365 = 6,200 kWh (95% offset)
Year-1 savings at 34c/kWh: A$2,108

System size by household consumption

Using 4.5 peak sun hours, 78% derate, 440 W panels, 90% target offset:

Monthly kWh	Annual kWh	System kW	Panels	Daily kWh	Year-1 savings*
400	4,800	3.52	8	12.36	A$1,469
542	6,504	4.84	11	17.00	A$1,990
700	8,400	6.16	14	21.62	A$2,571
900	10,800	7.92	18	27.80	A$3,305
1,200	14,400	10.56	24	37.07	A$4,406
1,500	18,000	13.20	30	46.34	A$5,508

*At 34c/kWh blended residential rate. State FiT not included.

What changes the result

Peak sun hours by capital city

BoM 2026 Solar Resource Maps confirm:

3.4 kW in Darwin at 5.7 PSH (8 panels)
4.0 kW in Perth at 5.4 PSH (10 panels)
4.4 kW in Brisbane at 4.9 PSH (10 panels)
4.6 kW in Adelaide at 4.7 PSH (11 panels)
4.84 kW in Sydney at 4.5 PSH (11 panels)
5.4 kW in Melbourne at 4.0 PSH (13 panels)
6.0 kW in Hobart at 3.6 PSH (14 panels)

Same 6,504 kWh/year household, same 90% target offset.

State feed-in tariffs

The savings figure assumes 100% self-consumption. Australian households typically self-consume 30–40% of generation without a battery, 70–85% with one. Exported kWh earn the FiT:

NSW Solar Boost (Origin): 11.4c/kWh first 14 kWh/day, then 7c
Victoria ESC minimum: 4.9c/kWh (some retailers offer 12c+ on 12-month contracts)
South Australia Tango: 12c/kWh
Queensland Ergon Energy regional: 12c/kWh
Queensland SEQ retailers: 6–8c/kWh
WA Synergy DEBS: 10c/kWh peak (3-9pm), 2.75c off-peak
Tasmania Aurora: 10.869c/kWh
ACT ActewAGL: 9c/kWh
NT Jacana: 9.13c/kWh

Source: AER + state regulator websites, April 2026. Battery storage time-shifts exports — a 10 kWh battery raises self-consumption to 75% on a typical 6.6 kW system.

Panel orientation and tilt

The reference case is north-facing at latitude tilt (33° in Sydney, 38° in Melbourne, 28° in Brisbane). Off-axis penalties (CEC Design Guidelines):

East or west: 12–18% loss versus north
South: 25–30% loss (avoid in residential design)
Flat (0° tilt): 8–12% loss

Many Australian homes have east-west roof aligned with street frontage — split-array installs (panels on both pitches) lose only 5–8% versus a hypothetical north-facing equivalent and capture morning + afternoon load profiles better.

Soiling

Australian soiling losses (CEC + SunWiz fleet data 2026):

Coastal humid (Sydney, Brisbane, Melbourne): 2–3% annual
Inland dry (Adelaide, Perth, Canberra): 4–6%
Rural dust (NSW Riverina, Central QLD, WA wheatbelt): 6–10%
Bushfire-affected periods: spike to 15–25% during smoke events

The cleaning cost calculator walks through whether annual cleaning is economic for your postcode.

Why size from kWh, not from roof space

Roof-area sizing is the planning-stage shortcut. kWh sizing is what eliminates a bill. The Clean Energy Council 2026 best-practice guide confirms: kWh-driven sizing is the standard for any quote that meets the CEC New Energy Tech Consumer Code.

The right workflow:

Sum 12 months of bills. Add projected load if you are buying an EV (3,500–4,500 kWh/yr at 15,000 km) or heat pump hot water (1,800 kWh/yr replacing gas, per Sustainability Victoria).
Decide your offset target. Without battery: 90–110%. With battery: 100–130%.
Run this calculator with local PSH from BoM.
Sanity-check roof area: each 440 W panel needs ~2.0 sq m. A 6.6 kW system needs ~30 sq m of unshaded north-facing roof.
Get CEC-accredited installer quotes — required for STC rebate eligibility under the Small-scale Renewable Energy Scheme.

Common mistakes

Sizing under 6.6 kW because of “the rule”: 6.6 kW with a 5 kW inverter clears STC thresholds and stays inside DNSP export limits in most states. But if you use 8,000+ kWh/year, oversize the panels (10 kW DC) with a 5 kW inverter and the STCs still apply.
Ignoring time-of-use tariffs: Most Australian states have rolled out smart meters. A flat 34c/kWh assumption overstates savings if you use ToU and most consumption is overnight (off-peak 18c). Match self-consumption to the tariff structure.
Forgetting state battery rebates: NSW Peak Demand Reduction Scheme (≈$1,200 for 10 kWh), Victoria Solar Homes battery loan, WA Distributed Energy Buyback Scheme — these significantly change the optimal system + battery split.
Using a single CEC-accredited quote: Get three. SunWiz Q1 2026 data shows a 25–35% spread between cheapest and most expensive quote for identical system specs in the same postcode.

Sources

Bureau of Meteorology Solar Resource Maps — peak sun hours for any Australian location
Clean Energy Council Design Guidelines 2026 — installation standards and AS/NZS 5033 compliance
AER Default Market Offer 2025-26 — Australian residential kWh and tariff benchmarks
SunWiz Australian Solar PV Q1 2026 — installation, performance, and pricing data
Clean Energy Regulator postcode data — installation and STC certificate database
AS/NZS 5033:2021 — installation and safety requirements for PV arrays

Frequently asked questions

How many kWh does a solar panel produce per day in Australia?

A 440 W residential panel at 4.5 peak sun hours and a 78% derate produces about 1.54 kWh per day (440 × 4.5 × 0.78 / 1000). Annualised that is 564 kWh per panel per year. The Clean Energy Council 2026 design guidelines cite 1,500–1,800 kWh per kWp for most Australian capital cities, which our calculator matches when you scale by panel count. Brisbane and Perth deliver higher yields (1,700+ kWh/kWp), Hobart and Melbourne lower (1,300–1,450 kWh/kWp).

What is the average Australian household electricity consumption?

AER's 2026 Default Market Offer benchmarks average residential household consumption at 6,500 kWh/year (542 kWh/month) for a typical four-person home. Single-occupant flats: 2,400 kWh/year. Large all-electric homes with pool, ducted AC, and EV: 12,000–18,000 kWh/year. SunWiz and the Clean Energy Regulator postcode database show actual consumption varies 30–40% across Sydney suburbs alone — pull your last 12 months from your retailer's app.

Should I aim for 100% offset or less?

Australian residential solar increasingly sizes for 100–150% of consumption because state and retailer feed-in tariffs (FiTs) remain reasonable for new connections — NSW Solar Boost 11.4c/kWh, Victoria's ESC minimum 4.9c, South Australia's Tango 12c, Queensland Ergon 12c regional. Self-consumption is still worth more (33–35c retail), but exports earn enough to justify oversizing. With a battery, target 100–120%. Without one, 90–110% is the economic sweet spot in most states.

Why is my actual production lower than the calculator says?

Three common Australian causes. First, dust and bushfire smoke — Melbourne's 2020 Black Summer cost residents 8–15% of annual generation. Soiling losses in dry, dusty postcodes (rural NSW, central Queensland) run 5–7% versus the 2% calculator default. Second, west-facing arrays — common in Perth and SA single-storey homes — give up 8–12% versus north. Third, hot rooftop panels above 50°C can lose 15–20% momentary output; SunWiz's H1 2026 fleet data confirms this in summer.

How does panel wattage affect the count?

Higher-wattage panels mean fewer panels for the same kW. A 6.6 kW system (the standard CEC-recommended size) needs 15 panels at 440 W, 13 at 510 W, 11 at 600 W (Trina Vertex, JinkoSolar Tiger Neo). Roof real estate matters — typical Australian three-bed home has 25–40 sq m of north-facing roof, fitting 12–18 standard 440 W panels. Higher-wattage modules unlock more kW from a small roof and clear the 6.6 kW STC threshold for STCs at 5 kW inverter limits.

Solar Panels kWh Calculator