Is your rooftop solar performing as well as it should? Data says… probably not

Some 75% of residential rooftop solar systems are not passing on the full extent of electricity bill savings they are capable of delivering, new data has revealed – either because they are not working properly or because they are paired with the wrong retail energy deal.

Using data from its own pool of 35,000 customers, as well as data from industry statisticians SunWiz, solar monitoring company Solar Analytics says a significant number of Australia’s 3.3 million rooftop solar systems are likely to be underperforming.

For its own customers, this is not a problem for long – Solar Analytics’ monitoring is designed to detect system faults and get them sorted as quickly as possible, while also offering weekly updates on the best energy deal to optimise each household’s solar savings.

But for those who don’t have solar monitoring and aren’t retired engineers, it can be easy to miss the signs of an underperforming solar system.

Stefan Jarnason, the co-founder and CEO of Solar Analytics, says it could take a regular household up to three months to notice even a major drop off in solar production reflected in their energy bill.

But in more marginal cases, some households might never notice that they are not saving as much as they could be – or had done before – if their system was working to its full capacity or paired with a better retail deal.

“At the moment, it’s even more difficult to know because, right now, …you’ve got two complicating factors: First is lots of people are working from home and seasons are changing – they might be changing how they use energy, so their energy use is more variable over the last year or two.

“The other [complicating factor] … is energy prices are going up and they’re about to go up by another 23% in July again,” he says, so any loss of solar production might get put down to that.

“So it’s hard for someone who sees their bill go, say, $20 a month to paying $80 a month. Is that because something’s wrong? I’m on the wrong plan? Or because the energy cost… has just gone up?”

Meanwhile, the extra savings that can be made the early detection of faults, or through switching to better plans, can be far from marginal.

Solar Analytics estimates that using monitoring software to identify and fix any faults with your rooftop solar system faster can save an average rooftop PV owner $312 a year. While being on the wrong electricity plan can cost a household an extra $400 a year or more.

How do you know if you’re not getting the right bang for buck?

The best way for most would be to invest in solar monitoring. There are a number of options available for this, including that some solar retailers or solar inverter brands offer the service as part of the installation – or as a small added cost during installation.

Then there are monitoring programs like Solar Analytics, but of course these are not generally free. Currently, Solar Analytics does offer a software only option for their monitoring service, at $60 a year – and you can also do a free 30-day trial first to try it out.

If you don’t have or want monitoring, the next best bet is to get your system serviced regularly, to make sure it’s working to its best capabilities. And to check if you’re on the best retail plan, there’s always services like Energy Made Easy, a federal government site, or other state-based offerings.

My solar is working, I’m on a good plan, but my bill’s still going up – what next?

“I guess the next big thing …which our customers are asking is what can I do about it if I still get a higher energy bill,” says Jarnason.

“What solar customers want is a tiny bill,” he adds, and there are a few ways to help that happen, including installing as much solar as possible.

“As an environmentalist, my advice is to cover your roof,” he tells One Step Off The Grid. “As a pragmatist, it’s put on as much as you can afford.”

Beyond this point, things are a bit less black and white.

Jarnason says that, currently, according to Solar Analytics analysis, only 10% of solar households will make a positive return on investment in a home battery. But that’s likely to jump to around 30% within months, as grid energy prices rise again in June. In the longer term, battery economics are also expected to improve.

“We have a battery calculator which says, okay, here’s all the different sizes of batteries you could get, here’s one we’re recommending because, based on your usage, it will give you the best return on investment … and if you get that battery, here’s the best plan for you. Here’s how much you’ll now be grid independent – here’s what it’ll cost here’s the return on investment.

“So we’re not pushing batteries. We have no stake in your getting a battery or not. What we’re doing is just giving you independent, unbiased, accurate information on what [a battery] would actually do for you and if you want to get one, then go ahead.”

And the next frontier for Solar Analaytics is hot water – setting up a calculator to work out the cost benefit analysis for switching a customer from gas to electric.

For now, Jarnason’s best estimates from the research done so far is that it makes good economic sense for two out of three people with gas hot water systems to switch to heat pumps.

Stefan Jarnason’s economic rule of thumb for energy independence and decarbonisation:

“Cover your roof with solar, get off the gas, add a battery, and then buy an electric vehicle. That’s the order of economic value for the typical person,” he tells One Step.

“And if you drive more than – I think it’s 15,000km or 20,000km a year; get solar first, then get an EV, and then get off the gas and get a battery.”