This applies for example when you want to add a photovoltaics installation to your campervan, expedition vehicle, garden hut, off-grid house or similar. For having enough electricity year-round from photovoltaics alone, battery size and module size have to be properly dimensioned.
The best tool I found for this is the European Commission JRC's PV potential estimation utility. There, use the last tab "Stand-alone PV".
Note that that the tilting angle of the solar panels is important in winter. Differences of up to ca. 30° from the optimum have no large effect, but above that they get quite important. So having an angle of 0° (flat panels) while you should have an angle of 74° (Germany in winter for example) means you get only about 25% of the power you would get at a 74° angle. You can calculate the exact numbers for this with the SunAngle calculator.