This is an excellent question. It’s no surprise that we have no shortage of sun in Hawaii, but you may be surprised to learn that a PV system does not necessarily need direct sunlight in order to be effective.
All it really needs is daylight. Even if you live in the shadow of a hillside or your property is covered with shade from abundant vegetation, you can still benefit from a PV system. That said, direct sunlight is always better — ideally, you want your PV panels exposed to the sun for at least six hours a day, between 9 AM and 3 PM. (Though Hawaii is fairly far south on the globe, we are still north of the Equator, and PV panels on the islands should be oriented southward in order to get the full benefit.)
But exactly how much sun do you need, and how is it measured?
How much sun you need depends on how much electricity you typically use. An energy-efficient home — one with energy-efficient appliances or low usage rates from its occupants — is going to need fewer photovoltaics than one that’s running a large number of high-load devices. Chances are you will have to get a professional assessment of your home and load potential in order to determine exactly how much photovoltaics you will need in order to zero out your bill.
Measuring sunlight is another matter altogether. Sun-recording instruments are expensive and delicate, precision devices. One of these is known as a pyranometer, which consists of a transparent dome over a round, flat plate. A thermophile (a type of radiation sensor that gauges the intensity of light waves) is used to measure the temperature of the plate’s surface as it heats up, which in turn will provide a measurement of the voltage potential. A few digital alternatives exist as well.
In Hawaii, the State’s Department of Business, Economic Development and Tourism (DBEDT) provides solar ‘sun zone’ maps. Each sun zone provides an average production via effective ‘sun-hours’. These sun-hours provide a great way to estimate daily production for a PV system and effectively size your system to zero out your energy bill!
To get the best answer to these questions, a professional solar integrator like Sunetric will come to your home and take these measurements for you prior to design and installation to ensure the most cost-effective, energy-efficient solution. Many contractors will abide by the sun zone estimates when determining accurate production for your home, thereby making it unnecessary to use a pyranometer to measure solar irradiation at your home. The importance of this dedication to accurate property assessment and system design cannot be overstated, and it’s important to choose a solar contractor whose experience and knowledge can serve you best.
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Find out how much you could save with a Sunetric-installed system.