With winter solstice – the shortest day of the year – upon us, it’s an appropriate time to bust another myth about rooftop solar panels.
While today may be the shortest day, owners of rooftop solar power systems aren’t necessarily shaking their fists at the sky, gnashing their teeth and rending their garments. Winter is still a good time for solar electricity production.
A popular misconception is that solar panels work best on the hottest days. This simply isn’t true – in fact it’s quite the opposite. Heat is the enemy of solar panels; it’s just that during summer the days are far longer which more than makes up for the impact.
Like solar inverters, not all solar panels are created equal and it’s the impact of heat that is one of the critical aspects that sets brands apart. An important module specification is called “temperature coefficient”. If the temperature coefficient rating of a panel is -0.46%, this means for each degree over standard testing conditions (STC – 25 degrees Celsius) the module’s output is reduced by -0.46%.
Cooler weather is the friend of solar as panels become more efficient in turning the sun’s rays into electricity. A blue-sky winter’s day can see some amazing levels of power produced on an hourly basis compared with summer.
Where winter does have a marked impact on production is in relation to cloud cover and shorter sun-hours – and this does drag down overall electricity output compared to the summer months.
To illustrate the differences throughout the year; here’s a look at the average annual solar irradiation levels in Melbourne and Sydney:
Melbourne may not be renowned for clear sunny days during winter, but as the above graph shows, Melbourne certainly experiences enough sunlight to make solar panels more than viable.
To determine solar radiation resources in your area throughout the year, try Energy Matters’ solar quotes tool, which will generate estimated electricity production per month, year, carbon emissions reductions and financial benefit information based on your location and the size of the system you select.
For solar power system owners, a clear sky on a winter’s day – however cold or short it may be – warms their hearts and lines their pockets through electricity bill savings; plus takes off the chill associated with the prospect of continually increasing electricity prices.