does it matter when i use most power?

kells said:

Hi All,
i live in spain and am of grid and installing a solar panel system. I am told ,that to calculate the number of panels and batteries needed, I need the to predict the total Kwh i need per day. Is it not important when the more 'thirsty' electrical items are used?

As Bill has eluded to, it certainly does. Many solar calculators don't take into account seasonal variations. My energy use matches my available energy quite well. I air condition during the summer, and use wood heat during the cloudy winter.

While I might use 12-15 kwh's of energy during the summer, a calculator might assume I need that during the winter and oversize my system many times over. In the winter, I run around 2 kwh's a day.

There is also a learning curve I'm sure all/most have experienced over time, the details which could never be accurately accounted for in a calculation. Seasonal variations are the biggest challenge as timing when to use excess power is a moving target, albeit a slow moving one, it takes at least a year to understand how the system will perform, naturally weather is unpredictable so having a backup generator is useful. At first I waited until float was reached before doing laundry, which was usually after 13:00h, later I began after the first hour of absorption ~11:30h  because the battery requiments were well below array capacity, this is one example of learning ones system. In my case being 17°N means there's little difference throughout the year in terms of hours of sunlight, the further north or south of the equator the bigger the difference, so adjustments to schedules wI'll be correspondingly greater. The single most important important load is a refrigerator, which may account for 50% of total useage ( never underestimate the refrigerator ). After charging loads obviously account for most of battery capacity so minimizing is crucial, the addition of a TV for example raised my consumption by ~0.5kWh per day according to monthly logs, over the years I did without. Off grid  living  requires a conservative mindset, unless of course money is no object, then anything is possible.