Last updated 23 September 2026
Quick answer: Open the free Solar Panel Angle Calculator, enter your roof’s direction, its tilt and your postcode. It shows the best direction and tilt for panels where you live, what percentage of that your roof captures, and for Australian postcodes the yearly kWh gap in real numbers.
This is the tool the other two feed into. Once you know which way your roof faces and how steep it is, the obvious question is: so how good is that? Installers will tell you north at latitude is ideal, but nobody tells you what a west facing roof at 20° actually costs you. This calculator does, in a few seconds, and the answer is usually smaller than you’d think.
What is the Solar Panel Angle Calculator for?
It compares your roof’s orientation with the best possible fixed angle at your location and gives you a percentage. 100% means facing the equator at close to the ideal tilt. A Sydney roof facing west at 20° comes out around 85%. It also tells you the ideal tilt for your latitude and, if you enter an Australian postcode, roughly how many kWh per kW you’d get each year compared with the ideal.
Under the hood it runs a typical year of real weather from the European Commission’s PVGIS service through the same model as our orientation comparison, checked against NREL’s PVWatts. We wrote about what the results mean in does the perfect solar panel angle actually matter. This post is about driving the tool.
How do I use it?
Step one: set the direction. The azimuth slider runs from 0° (north) through 90° (east), 180° (south) and 270° (west). If you measured your roof with the Roof Azimuth Calculator and clicked the link under its result, this is already filled in.
Step two: set the tilt. Most Australian roofs are 15° to 25°, and 22.5° is the most common. The Roof Tilt Calculator passes this across the same way.
Step three: tell it where you are. In Australia, type your four digit postcode and the tool picks the nearest reference town and its typical-year weather. Anywhere else, or if you’d rather be precise, enter your latitude directly. Southern hemisphere latitudes are negative, so Sydney is about -33.9. If you don’t know it, the Latitude and Longitude Finder will get it from your address.
The result updates as you move the sliders, so it’s worth playing. Drag the azimuth around and watch how little the percentage moves between north east and north west.
How do I read the result?
At the top is the best angle for where you are, for example north facing and tilted 33° in Sydney. Under it, the big number is your roof’s percentage of that best case, followed by a one line verdict: 95% and above is excellent, 85% and above is very good, 70% and above is workable, and below that you’d want to look at another roof section. There’s also the range of tilts that stays within 2% of the best, which in Sydney runs from about 21° to 45°, wide enough to cover almost any normal roof pitch.
With an Australian postcode you also get the yearly kWh per kW for your roof against the ideal, and for gaps bigger than 20 kWh a line scaling it up to a typical 10 kW home system. An 85% roof in Sydney gives up roughly 2,400 kWh a year. Noticeable, but far less than most people expect. For real kWh at your exact address, season by season, the result links through to the Solar Orientation Comparison.
What’s the heatmap?
Below the result is a colour map of every direction across the bottom and every tilt from flat to 45° up the side, with a dot showing your roof. It’s the quickest way to see the shape of the problem: a big green blob around north, and colour only really dropping off as you swing towards south. Worth a screenshot if you’re explaining to someone why their east facing roof is fine.
Is it accurate for my address?
It’s based on your latitude and a typical year of real weather for your region, so treat it as a solid indicative figure rather than a quote. It doesn’t know about your local microclimate or shading, and shading in particular can matter more than orientation. A chimney shadow across one panel for two hours a day can cost more than facing the wrong way entirely.
Already have solar?
Orientation sets the ceiling on what your system can produce. Faults decide whether it gets there. That’s the part nobody checks, because the inverter app shows a green tick even when a string has dropped out. PV Fleet connects to the monitoring you already have, works out what your system should be producing given the weather and the season, and alerts you within hours when it falls short. Book a free demo if you look after commercial sites, or read why solar systems quietly underperform first.
All six free tools (roof azimuth, roof tilt, panel angle, roof area and panel count, a latitude and longitude finder, and a solar orientation comparison) are on the free solar tools page. No signup, and they work for any address.