We all know that solar panels need direct sunlight in order for them to generate their maximum power output. But with the sun constantly moving across the sky, it can be difficult to know when exactly this will happen.
The answer to this is both simple… and complicated.
Solar panels are most efficient at solar noon.
And while this answer is simple, it should be noted that solar noon and lunchtime noon are not the same thing – hence the complication.
Further exacerbating the confusion is the fact that solar noon is constantly changing and sometimes by a lot, according to the season and where you live on the planet.
What Is Solar Noon?
Solar noon, or sometimes referred to as ‘high noon’, is the moment where the sun hangs at its highest point in the sky.
In a situation where the earth spun true, solar noon would be the same time everyday, regardless of where you lived.
However, since the earth tilts back and forth, the angle of the sun changes with the seasons. This means that high noon will be a different clock time according to the tilting of the planet.
For example, on January 1st, 2020, Chicago experienced solar noon at 12:37pm – 37 minutes after lunchtime noon.
Fast forward to June 1st, 2020 and solar noon for Chicago came at 1:32pm – almost an hour later than it had just six months earlier.
And the farther you get away from the equator, the more dramatic the difference between clock noon and solar noon.
Anchorage Alaska, for example, saw solar noon at 1:57pm on June 1st – almost two hours after lunchtime noon.
##Tools To Help ##
A really great tool for understanding when solar noon will happen for your location is the NOAA Solar Calculator. Simply select a major city close to your address and this calculator will provide you with a wealth of really great info.
(*Dates can be input for planning events where sunlight hours play a role in your endeavors.)
Practical Solar Panel Efficiency Time-Range
While solar noon promises the optimum angle for power generation, this does not mean that a solar array will be sitting idle during daylight hours.
For us, in our off-grid home, the summer months will see our battery bank fully charged generally before lunch – meaning before solar noon even occurs.
This is actually quite extraordinary as our home has central air, 3 flushing toilets, a heat-pump hot water heater, microwave, fridge, etc. So even when household power demand is at its highest, our needs are easily met as the sun is shinning for longer hours.
Based on this experience, a practical efficiency range for our solar panels in summer, is between 9am to 7pm – a relatively long length of time.
Unfortunately, this is not the case for the winter season.
Because of the angle of the sun and the seasonal cloud cover, it is not uncommon to see a very low output from our panels, even at solar noon. Point of fact, we will often have to run a back-up generator in order to have enough energy stored in the batteries to make it through the night – when household load is at its lowest.
Consequently, a practical efficiency range for our solar panels in the wintertime, is around 11am to 4pm – a considerably shorter length of time than that of summer.
Living off-grid, we power our home primarily through our solar panels. And having done so for a number of years, we have come to truly appreciate/understand the seasonal aspects of solar power.
In the summer, we’ve got more power than we could ever possibly use.
In the winter, we’re starved for it!
Knowing how the sun shines and when it is at its optimum, allows us to plan our day. For example, if it’s early in the morning and the skies are clear, we’ll try and look for something to run – like a load of laundry or the dishwasher.
If it’s past solar noon and the panels are struggling, we’ll wait on running the vacuum cleaner until we have a brighter day.
And while this might sound wildly inconvenient, it has actually become a non-event. Living with solar is as natural to us as cooking diner or having movie night with popcorn : )
So if you are considering unplugging from the norm and going solar, I highly recommend it!
##Tools To Help ##