What Size Solar System Do I Need to Run an Average Home?

Posted on January 17, 2019

It can be very overwhelming when you first start looking into getting a new solar system.

What size system do I really need? The ad on TV is for a 6.6kW, but the neighbours only have 5 panels on their roof. What does an average home need?

Firstly, we need to look at what is considered as an average home? According to Canstar1 the average NSW household has an annual electricity bill of $474.60 per quarter. Based on this we can estimate that the daily electricity consumption of this household will be about 14.5kWh/day2.

Some quick maths now. Given:

\text{Average Electricity Consumption} = 14.5{kWh}/{day} \text{Estimate for Peak Sun Hours (PSH)} = 5{hours}/{day} \text{Inefficiencies In A Solar System} = 10\%

We can calculate:

\frac{14.5{kWh}/{day}\times(100\%-10\%)}{5{hours/day}}=2.61kW

So this tells us a 2.61kW solar system will produce enough power to offset an average household’s electricity usage. That’s quite a modest size system. But what if they use 50% of their power at night, meaning only 7.25kWh of power can be offset during the day? Does that mean I only need 1.305kW (2.61kW/2) of solar now?

The good news is: batteries can provide you power at night!

The bad news is: batteries are quite expensive, at the moment, to save you money in the long term!

In the meantime, what we do is size a system for you so that it:

  • is sufficient to cover your daytime usage,
  • produces a little bit extra to cover times of heavy electricity usage,
  • earns you some credit in solar feed-in-tariffs.

This extra solar allowance should be sufficient so that when batteries are economically viable, you’ll be producing enough solar to be able to charge your battery up with your excess power.

So, we want a solar system that provides enough power to provide 7.25kWh of power throughout the day, and also enough to charge a battery at a later date, which will provide 7.25kWh at night. The closest size system we currently offer to 2.61kW is a 3.15kW solar system with a 3kW inverter. This system will comfortably supply an average household with enough power to offset their daytime consumption with some extra room to breathe.

There are several other considerations that can be made to determine the right size system for you:

  • How much suitable roof space you have
  • Whether you have any large electricity draws in your home (e.g. ducted air-conditioning)
  • Whether you have any shading considerations
  • Your power usage patterns as they may vary to what we’ve assumed above

This article was designed to give you an idea of what system is suitable for an average household. If you’d like more advice on what size system is suitable for you and your home, call our solar experts on (02) 4954 3310.

1 – Latest average recorded in January, 2019 – https://www.canstarblue.com.au/electricity/average-electricity-bills/
2 – Using $0.90/day supply charges and a $0.30/kWh rate, we get about 14.5kWh/day.