Frequently Asked Questions
What’s the difference between kWp and kWh?
kWp (kilowatt-peak) is the rated power of your solar array under lab conditions. kWh (kilowatt-hour) is the energy it actually produces or you consume.
How accurate is the PV output estimate?
The tool uses PVGIS 2005-2020 averages. Expect ±10 % variation with weather, shading and module type.
Why does the inverter size round up?
We round to the next whole kW so you can buy an off-the-shelf inverter size (e.g. 5 kW, 8 kW). Most brands allow a 10-20 % DC oversize anyway.
Can I oversize the panels vs. the inverter?
Yes. Modern string inverters tolerate up to 130 % DC/AC ratio; this boosts morning and late-afternoon harvest. Our quick calc uses a 1 : 1 ratio by default.
How do I choose battery autonomy hours?
Autonomy is how long you can run on battery alone. A fridge & lights might need just 4 h; full off-grid living may need 24 h +
Does roof colour or material affect output?
Roof material has negligible impact. Output is driven by tilt, orientation and shade. Dark tiles may warm panels slightly, but temperature losses are already baked into the PVGIS model.
I’m in the Southern Hemisphere—do I face north?
Yes. PVGIS treats 0 ° azimuth = South. In our wizard, a 180 ° azimuth means North-facing in South Africa, Australia, etc.
Can I export the report?
Click Save as PDF on the report page. A print-ready PDF with your inputs, monthly chart and sizing results downloads instantly.
Do I need batteries to use solar?
No. You can run a grid-tied system without batteries. The wizard’s Battery Autonomy slider can be set to 0 h to model a panels-plus-inverter-only design.
How often should I re-run the wizard?
At least once a year, or whenever your monthly kWh changes by 10 % or more (e.g. after adding a heat-pump geyser or EV charger). New tariff tables and irradiance updates are loaded automatically.
Will my roof fit the recommended array size?
The calculator focuses on energy sizing, not roof geometry. As a rule of thumb allocate 6 m² per kWp for modern 410 W modules. Measure usable roof area or ask an installer to confirm layout.
Do I need permission from my utility?
In most countries a grid-tied system must be registered. South African homes under 50 kVA submit the SSEG form; UK systems under 3.68 kW/phase file a G98 notification. The wizard report lists all specs required for these forms.
How much maintenance do solar panels need?
Panels are solid-state and need little care—just a visual check and a gentle wash with water if dust or bird droppings cut output by >5 %. Inverters and batteries have built-in self-diagnostics.
Why does the report show “clipping loss”?
If you oversize panels relative to inverter AC power, noon-time spikes can exceed the inverter limit. The excess is clipped. Our model shows annual % lost so you can judge if the extra panels are worth it.
Are my inputs stored on your server?
Your inputs are saved on our server for 7 days so that you can share alink to your report with your solar installer. After 7 days, all inputs and results are deleted and you will need to regenerate a fesh report if required.
Why do you ask for my location?
Solar power production is closely linked to where you are in the world, so without this information we cannot give you an accurate estimate fo your solar requirements.