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Suitably Sizing Solar



Once one has a firm grasp of the basics involved in a satisfactory solar install, a retailer and perhaps even a product in mind — the next thing to consider is what size suits your home.


Let’s look at how that works.


How That Works


The first question to be asked concerns your average energy consumption.


The amount of power you need the solar array to produce generally will dictate the number of panels and size of inverter required to match it..


1. Sensibly


By bringing up your most recent electric bill on your phone or tablet, you can find the standard daily kWhs for your home and an accompanying graph above it.


For sake of illustration, let’s say you use 15kWhs a day ordinarily.


To work out the minimum size of system needed to be equal to the task of meeting your normal usage, in the State of Victoria, you would divide 15.0 by 3.6. Where 15.0 is your consumption and 3.6 is the average amount of usable sunlight you can reasonably expect in Victoria.


15.0 ÷ 3.6 = 4.16.


Round up, so you’d have a 4.5kW array. This system would have a nominal output capacity of 16.2kWhs on 3.6 hours of usable sunlight. More than equal to your daily 15kWhs in this case.


Turning on the wattage of the panels, you’ll require somewhere between 17(270W)-13(360W).


2. Supersizing It


Above, we looked into sizing a solar solution suited exclusively to the task of taking care of your total consumption with a little bit of power to spare.


However, there are other factors to include in this equation. The amount you are committed to outlay, for example.


If you are willing to pay that bit extra, you can optionally oversize the array. Say, to a 6.0kW array. Set against your15kWhs daily consumption in the example above, it would do 21.6kWhs on 3.6hours of usable sunlight.


This will enable you to produce power well in excess of your own daytime needs. The overproduction goes back to the grid to be redistributed to your neighbours. Your energy retailer is obligated to pay you for each additional kWh you feed back in.


In Victoria, the local government has enforced a mandatory minimum of 11.3¢ per kWh fed back into the grid for all energy retailers with more than 5,000 customers.


There is also now a very generous offpeak—shoulder—peak option available.


As of 1 July Victoria's Essential Services Commission announced the following optional time-varying rates for solar homeowners,


Your off-peak rate will be 7.1¢ per kWh between 10PM-7AM

Your shoulder rate will be 10.3¢ per kWh between 7AM-3PM/9PM-10PM (weekdays)

Your peak rate will be 29.0¢ per kWh between 3PM-9PM (everyday)


Such a favourable state of affairs can allow you to potentially sizably offset your residual nighttime usage, winter bills and even the supply charge for the property.


3. Oversized is Better — Batteries, Best.


If you can commit to purchasing the full PV + Battery package you can realistically balance your self-production—self-consumption quota for the lion’s share of an Australian year.


Grid independence isn’t impossible anymore. You can take your electricity requirements by the scruff of the neck. Do!


The aim then would be to size the array to cover your daytime consumption and produce enough power plus besides to top up the battery for evening use, peak-shaving, load-shifting or back-up power.


On our running example of a home using 15kWhs daily with a 6.0KW PV array installed, on 3.6 hours of usable sunlight the system would produce, as said above, 21.6kWhs. More than an ample amount to fully charge the battery good to go in the evening and then some. The then some, would be sold back to the grid in exchange for credit.


In the event that for whatever reason some nights you were not using many appliances (holidays, travel for business, varying work-shifts, Tinder) — you can sell it back in the peak purchasing window when your feed-in tariff is highest: 29¢ on an optional off-peak—shoulder—peak feed-in tariff or the mandatory minimum of 11.3¢.


But don’t be put off even in the event that you stay conservative and sit on the 4.5KW. A battery can still be paired with the smaller array (but ideally no smaller than that).


To have us sort out sizing a solar solution tailoured to your home, be in touch today with a friendly, helpful and informative Astra consultant.


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