Solar panels are a great way to reduce your energy bills and this technology is used by more and more consumers now to future proof their homes or businesses against high energy bills.

it’s critical that you know how big system size you need to reduce your energy bills before you finish up with an oversized solar PV system This simple step by step guide will help you accurately calculate what size solar PV system you need

First, You may need to estimate a production goal that you’d like to achieve to reduce your energy bills. Your previous energy bill will help you edge your average peak energy usage to target your production goal.

To determine the PV array size needed, we also need to know the average daily peak sun-hours for your site, suburb or state. Once you’ve your annual kWh production goal and the peak sun-hour value, you can easily calculate required PV array size. Putting efficiency factor in this calculation may also be beneficial.

I must submit, The first step in going solar is not sizing the PV system, but reducing your electricity usage through energy management and efficiency measures. These measures help you keep control on the energy bills by making your home Energy efficient. Once these measures have been implemented, you’re ready to size a PV system to offset the remaining energy usage.

Let’s check this case study

Let’s assume we are sizing a solar power system for property located in SYDNEY, NSW.

After implementing energy-efficiency strategies, this home consumes an average of 20 kWh a day. A total annual energy consumption estimate of 7,300 kWh per year (20 kWh * 365 Days). Using solar data for Sydney, supplied by the ABS (Australian Bureau of Statistics) you’ll find the average peak sun-hours per day for a north-facing array, mounted with tilt equal to latitude (in this case, 30°) to calculate the array size needed to meet our predicted annual energy consumption as below.

As you know solar can only offset your morning usage through solar generation and you still need to purchase energy you use during the night as well as times when solar is not producing power.

Let’s say you use 60 % energy during the day and 40% during the night out of Total 20 kWh daily usage. This sums 12 kWh used during the day and 8 kWh during the night.

Let’s aim to offset morning usage of 12kwh you may do calculation as below

To offset 100% of the home’s morning electricity consumption over the course of a year, a 3.21 kW system is needed. You could upsize your system considering future demand increases and equipment upgrades. Oversized system can also offset a portion of night usage through FITs available.

The 0.72 efficiency factor is based on the following assumptions: average solar access of 95% (shading derate factor); modules with a positive-only production tolerance; inverter efficiency of 96%; module temperature derate factor of 0.88; DC and AC wiring derate of 0.98 and 0.99; module soiling derate = 0.95; module mismatch derate = 0.98; system availability derate = 0.99: