How much power would a balcony solar system make in Perth?

Perth gets a lot of sun, but a balcony is a tricky place to catch it. Most balcony kits hang flat against a rail, many balconies face the wrong way, and the floor above often throws shade. The numbers below are my own rough estimates from a public solar model, not measurements and not figures from the WA Government. No plug-in kit is legal in WA yet, so nobody has real Perth results to report.

How were these estimates worked out?

I ran NLR’s PVWatts model (the US National Laboratory of the Rockies, formerly NREL) through its public API on 5 November 2026. PVWatts estimates the output of grid-connected solar anywhere in the world from typical-year weather data. For Perth it used satellite-based NSRDB Himawari typical-year data for the point I gave it.

Inputs used for every run unless stated:

Input	Value
Location	latitude -31.95, longitude 115.86 (central Perth)
Panel size	0.8 kW DC (for example two panels of about 400 W)
Inverter	0.8 kW AC (DC to AC ratio 1.0), default 96% efficiency
System losses	14%
Module type	Standard
Mounting	Fixed, open rack (air behind the panels)
Shade	None modelled

In PVWatts, north is an azimuth of 0 degrees, east 90, south 180 and west 270. Tilt is measured from flat, so a panel hanging straight down a balcony rail is 90 degrees.

How much does direction and angle change output?

A lot. Here are the annual results, rounded:

Direction	Tilt	Rough estimate (kWh a year)	Compared with north at 30°
North	30°	about 1,350	100%
West	30°	about 1,135	about 84%
East	30°	about 1,125	about 83%
North	90° (vertical rail)	about 770	about 57%
West	90° (vertical rail)	about 685	about 51%
East	90° (vertical rail)	about 670	about 50%
South	90° (vertical rail)	not given, see below

In plain terms: a tilted panel facing north is the best case, east or west tilted loses about a sixth, hanging it vertically on a rail loses close to half, and a south-facing balcony is the hardest case.

The draft standard does allow tilt. It describes a mounting system as one designed “to adjust the tilt angle of the PV modules” (section 3.1), and it says makers must specify panels be angled away from the mounting surface where that is needed for ventilation (section 5.5.1). Whether a tilted frame suits your balcony will depend on the kit’s permitted mounting types, wind loading and your strata or landlord.

Why does a vertical north panel do better in winter?

Because the winter sun sits low in the northern sky, so it hits a vertical panel more squarely. The monthly PVWatts figures for the 0.8 kW vertical north case show this clearly:

Month	North, vertical (kWh)	North, tilted 30° (kWh)
January	about 36	about 142
April	about 82	about 105
May	about 88	about 95
June	about 76	about 76
September	about 76	about 114
December	about 35	about 132

The vertical panel peaks in autumn and winter and makes its least in midsummer, when the sun is nearly overhead at noon. Vertical east and west panels do the opposite: their best months are December and January, and June is their weakest.

What does the 800 VA cap do?

It caps how much power can flow into your home at any moment. The draft limits the inverter to 800 VA and 3.5 A of output, and the panels (plus any battery) to 2,000 W DC (section 4.1). If the panels could make more than the inverter can pass, the extra is lost. This is called clipping.

I ran two more cases with the full 2.0 kW DC of panels behind a 0.8 kW AC inverter (DC to AC ratio 2.5), all else as above:

Setup	Rough estimate (kWh a year)
2.0 kW panels, north, 30°, with 0.8 kW inverter	about 2,405
Same panels with no inverter cap (for comparison)	about 3,365
2.0 kW panels, north, vertical, with 0.8 kW inverter	about 1,705

So in this rough model the cap throws away about 29% of what a tilted 2 kW array could make, but extra panels still add output. The monthly results show the biggest gain in winter: in June the 2 kW tilted array makes about twice what the 0.8 kW one does, against about 1.7 times in January. On a vertical rail the gain from extra panels is bigger because the panels rarely reach full output.

How much does shade cost?

None of the figures above include shade, and shade is often the biggest loss on a balcony. A balcony above yours, a solid wall, a neighbouring building or a tree can block the panel for hours a day. I have not modelled shade for Perth, so I cannot give you a fair percentage. Watch your balcony through a full day, ideally in both summer and winter, and note when direct sun reaches the spot where panels would hang.

How does this compare with Germany?

It is roughly in line, allowing for Perth’s stronger sun. Germany’s consumer advice centre, Verbraucherzentrale, says one 400 W panel hanging vertically on an unshaded south-facing balcony makes “etwa 280 Kilowattstunden” (about 280 kWh) a year. South faces the sun in Germany, the way north does here. My PVWatts estimate for 0.8 kW vertical north in Perth works out to about 385 kWh per 400 W, roughly a third more, though the two figures use different methods and are not a strict like-for-like comparison.

What could this be worth on a Synergy bill?

Only the part you use yourself. There are no export payments under the draft proposal, so power your home does not use at that moment earns nothing. At Synergy’s Home Plan (A1) rate of 33.2621 cents per kWh (from 1 July 2026), each kWh you use from your own panels saves about 33 cents.

As a rough example, if you used 60% of the 1,350 kWh from a north-facing tilted kit, that would be about 810 kWh, or about $270 a year. If you used 60% of the 770 kWh from a vertical north kit, that would be about 460 kWh, or about $150 a year. The 60% is an assumption for illustration, not a measured figure. The government’s estimate of around $240 a year is for a north-facing system and an average Perth consumer, and the FAQ says savings depend on orientation and system type. See cost and savings for payback examples and plug-in solar batteries for how a battery stores the midday surplus.