The Biggest Mistake People Make When Sizing Up A Solar System

If you don’t have a good understanding of your power consumption, sizing up a solar system can be a bit of a minefield.

We normally start off by explaining that the average output of a solar system in Sydney is about 4 times a system’s size.

For example, a 5kW system will output 20kWh a day, averaged out across the year. So if your usage was around 30kWh a day and you estimated that you could use around 60-70% of your power during the daytime, a 5kW system would be a good fit.

The problem with this approach of using yearly averages is that a solar system outputs a lot more power in summer compared to winter:

This can work great when a household uses lots of power in summer, for example, the air conditioner and the pool pumps can run on solar power all summer long without having to draw extra power from the grid. In winter, the reduced output is matched by a reduction in power consumption, especially if a house has gas heating.

But we have a lot of customers that actually use more power in winter compared to summer because of electric heating, and if the solar system isn’t sized up correctly it can result in a large & unexpected winter power bill, especially if a household just assumes the solar system will cover the extra power needed to run the heating.

Here is an example from one of our customers that shows a big spike in electricity consumption from May due to heating:

You can see in the spring months the solar system is sized pretty well.

In summer there are a few spikes where the air conditioner was left on all day, especially in January, but for the most part, all of the solar power was used in the home.

But when the colder weather hits in May, the output from the solar system drops while the electricity usage increases.

This is why using averages isn’t always the best way to maximise the benefit of your solar system.

In this example, we would consider the system to be too small.

In reality, this installation was limited by roof space, so this family on the Southern Highlands is doing a great job of using as much of the solar power in the home as it is being generated. However, we have many other customers who don’t have limitations who still end up installing a system that is too small.

Why You Should Install A Larger Solar System

You may be thinking, “but if I size up the system to my winter usage, I will generate way too much power in the summer.”

Yes. And that’s a good thing.

Firstly, feed-in tariffs for the solar power you export to the grid are now much higher than they were, to the point where many of our customers are installing as many solar panels as possible, irrespective of their energy usage.

They are now enjoying a credit each quarter from their energy retailer. For more information on how this strategy works, check out our blog post here: How To Eliminate Your Power Bill With Solar Power

Secondly, they now have the option to add battery storage when they are ready. A home battery such as Tesla Powerwall will capture any excess solar power to use during the evening. If you have time-of-use energy tariffs, this can save you a lot of money as the peak billing period from 2 pm to 8 pm on weekdays now often has a tariff of over 50 cents per kWh.

We can help you size up a solar system in just a few minutes

For more personalised information and advice, request a callback below and we will help you find the right solar system for your home or business. If you have your power bills handy, it doesn’t take more than a few minutes to go through your bills and work out a solar system that will be the best fit:

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