{"id":67587,"date":"2022-12-05T12:19:04","date_gmt":"2022-12-05T01:49:04","guid":{"rendered":"https:\/\/www.solarquotes.com.au\/blog\/?p=67587"},"modified":"2024-10-02T10:09:18","modified_gmt":"2024-10-02T00:39:18","slug":"beat-solar-oversize-rule","status":"publish","type":"post","link":"https:\/\/www.solarquotes.com.au\/blog\/beat-solar-oversize-rule\/","title":{"rendered":"How To Beat The Solar Panel Oversize Rule With Grid-Tied Solar And Batteries"},"content":{"rendered":"

\"Australian<\/p>\n

Breaking the infamous ‘133% \/ 75% Solar Oversize Rule’ won’t get you in trouble if you add a battery. Or will it? <\/strong><\/p>\n

It depends on who you ask…<\/strong><\/p>\n

But before we get to that, a brief history of the rule.<\/p>\n

The Australian Solar Panel Array Oversize Rule<\/h2>\n

Why do solar companies everywhere offer 6.6 kW of solar<\/a> as their standard offer?<\/p>\n

It’s because of the rules. Or, to be more specific, the “Clean Energy Council Guidelines For Grid-Connected Solar PV Systems (No Storage)<\/a>“. This is a set of guidelines that must be followed when designing and installing solar power systems.<\/p>\n

If your solar designer does not follow them, you are not eligible for the STCs on the system. In other words, you won’t get the ‘solar rebate<\/a>‘, and your system will be thousands of dollars more expensive1<\/a><\/sup>.<\/p>\n

We are talking specifically about “Guideline 4.4 : Array peak power – inverter sizing”:<\/p>\n

4.4.1<\/strong> In order to facilitate the efficient design of PV systems, the inverter nominal AC power output cannot be less than 75 per cent of the array peak power and it shall not be outside the inverter manufacturer\u2019s maximum allowable array size specifications.<\/p><\/blockquote>\n

The first part of this rule is the one that matters here: “the inverter nominal AC power output cannot<\/strong> be less than 75 per cent of the array peak power”.<\/p>\n

Or, to put it the other, more intuitive way…<\/p>\n

The solar panel array cannot be more than 133%2<\/a><\/sup> of the inverter’s size in kW.<\/p>\n

History Of ‘The Oversize Rule’<\/h2>\n

Back in ye olden days of solar, shortly after the Renewable Energy Target was conceived, the Small Technology Certificates (STC) scheme was invented as a way to separate out the financial incentives for large (100 kW+) and small solar systems based on their theoretical carbon abatement. Essentially it was a carbon tax introduced by John Howard, but luckily the troglodytes were never bright enough to realise or stupid enough to politicise it.<\/p>\n

When you install a solar thermal hot water unit, heat pump hot water<\/a> or solar PV<\/a>, there is a value attached to the abatement of greenhouse pollution. You get paid upfront for the coal and gas you don’t burn from now until 2030.<\/p>\n

STCs for solar are based in part on how many watts of solar panels<\/a> are installed. But what if you install more kilowatts of panels than the inverter is nominally rated for? That could result in slightly less kWh of energy per kW of panels installed than a solar array that matched the inverter output.<\/p>\n

Bureaucrats hate anomalies like that, so it was decided to limit any oversizing to 133%. \u00a0By their judgement, 133% would make good use of the hardware and deliver the best efficiency in terms of money spent for carbon abated.<\/p>\n

The thing is that solar inverter manufacturers invariably rated<\/em> their machines for way more than 133%. You could wire up 150% or even 200% of the inverter nameplate capacity, and it would simply work closer to its maximum throughput for more of its life.<\/p>\n

Of course, there are times of good insolation when the inverter wouldn’t be able to handle all of the available energy, it would clip the output, running flat out for an hour or two in the middle of the day. But for most of the day the inverter would be passing through more useful energy than a non-oversized system.<\/p>\n

‘The Rule’ Is Way Past Its Sell-By Date<\/h2>\n

Before the CEC even existed,\u00a0SEIA<\/a> were the local industry body. It was a union of like-minded professionals who assembled a standards, training and assessment panel, which in turn wrote a document entitled “Advice on Best Practice”. This was a well-meaning ‘code of conduct’, circa 2007 that was tweaked by 5% and adopted by the CEC as a hard rule without further scrutiny.<\/p>\n

The CEC members’ area links to a document explaining\u00a0the rationale behind the rule. The latest version is dated February 2013.<\/p>\n

\"CECJustifying the rule, it says:<\/p>\n

“We believe that this limitation will allow the best possible design for the vast majority of cases while still allowing flexibility.<\/p>\n

 <\/p>\n

At this value, systems installed in the optimum orientation and tilt angle will not suffer greatly from yield loss and also allows for some oversizing to offset losses due to non \u2013 optimum installation locations. “<\/p><\/blockquote>\n

Unfortunately, this rule heralds from a time when:<\/p>\n