How the networks fiddle with data to trash rooftop solar PV

Networks across Australia appear to be launching a major campaign to curb the growth of rooftop solar PV – introducing or proposing tariff changes such as high fixed network costs or “demand charges” that penalise rooftop solar and are designed to slow installation rates.

As part of this campaign, the networks are using data that they say “proves” that rooftop solar PV is not reducing peak demand, and therefore not contributing to the grid. They use this to justify changing tariffs to reflect the “cost” of rooftop solar, but not its benefits.

South Australia Power Networks did this while arguing the case for “demand tariffs”, an initiative that it admits will halve the rate of solar installations over the next five years, and penalise solar households with added costs.

But the data has been challenged by the energy energy researchers at UNSW’s Centre for Energy and Environmental Markets and School of PV and Renewable Energy Engineering, who argue that SAPN has not been forthcoming with the whole picture about the contribution of rooftop solar PV.

In its submission, SAPN uses the example of a stinking hot day, January 16, 2014, in the middle of a major heat wave, to show that rooftop solar PV did not contribute much at the peak.

But here’s the thing. You will note that the SAPN graph includes only “exports” from the more than 400MW of  solar that was then on the rooftops of the state’s houses and businesses. (There is now more than 500MW).

But what happens when the total output from rooftop solar is included?

This graph below – provided UNSW team, using data from the Australian PV Institute – paints a completely different picture: It shows that rooftop solar PV did in fact reduce the peak by a considerable margin on that day.

It could be assumed that the solar households were consuming a lot of their output at that time because they, too, would have had the air-con on, because as the graph shows it was still 40°C outside.

(It should also be noted that SAPN used just residential demand, while the UNSW graph included overall demand, the key measure of network usage).

Iain MacGill , the joint director for CEEM, says UNSW researchers have concerns that such reports as the SAPN discussion paper is using selected data that is not generally publicly available, and hence subject to independent review.

“Their (SAPN’s) plot of solar PV’s contribution is potentially misleading because it shows estimated PV exports rather than PV’s contribution (self consumption as well as exports),” MacGill says.

“Whilst this may reflect the realities of net metering of PV, it does mean that the role of household PV in reducing overall residential demand is not made clear, because exports will naturally fall away as PV falls while household demand increases.

“Also, residential solar PV doesn’t only play a role in reducing residential demand, but assists in managing State wide peaks as well.

“It seems pretty clear that PV in SA actually provided a very useful reduction in peak demand of over 100MW whilst also delaying the peak for a couple of hours.”

Indeed, this is the very conclusion that SAPN came to itself in a presentation to analysts last year – using data from the very same day – January 16, 2014.

It published this graph above to show how rooftop solar had not just shifted the peak from the mid to late afternoon, but also lowered it considerably in comparison to the previous heat wave in 2009.  “PV is shifting (the) peak, but also helping reduce stress on the network during heat-waves,” it said in its presentation.

The problem with SAPN’s proposed demand tariffs is that rooftop solar is not credited with any network benefit.

If the timing of an individual household’s maximum consumption happens to outside of this peak demand, such as late afternoon, it means they could still face massive “demand charges” even though it correlates to one of the lowest demand periods for the networks.

The efforts to install “demand tariffs” are part of a broader process of introducing more “cost reflective” tariffs.

But what seems to be happening, however, is that the largest cross subsidies – between city and remote rural households, and for air conditioning – aren’t being touched.

Instead solar PV seems to be a major point of focus – perhaps not surprising since that takes revenue away, but very problematic for clean energy transformation and genuine equity between customers.

By speading the time, number of days and months as widely as possible, the networks are giving themselves a pretty good chance of picking up a particular period of high demand in a house for whatever reason.

The solar industry says that is unfair. Some say it could result in solar rooftop arrays increasing bills rather than leading to a fall. Encouraging battery storage is a good idea, but many households can not afford storage now, yet they risk being penalised for using high amounts of electricity in off-peak periods, when their rooftop solar is actually helping reduce peak demand.