Cellular vs WiFi for solar monitoring and control: how do they stack up?

South Australia is leading the nation on a new regulatory regime for controlling grid exports from rooftop solar systems. It can’t be long, however, before people start to question the reliability of the communications options being deployed to enable remote control?

Here’s the rub: WiFi communications to the cloud is significantly lower cost to buy and operate if you only look at things in data carriage terms. But making it operationally reliable over time can be an operationally-fraught experience, and it can quickly get resource-intensive and costly!

For starters, with WiFi, you often are reliant on the household’s WiFi router and cloud connection. Think about it. We’re talking about running a regulated utility requirement on the household’s own, self-run communications asset.

What could possibly go wrong?

Let’s say that your smart energy monitoring and control device has a wireless connection from the electricity meter box, usually outside the home, to the router which typically is located inside the home (this is the configuration handled by the Wattwatchers Auditor 6W* … yes, alongside our dominant cellular-communicating products, we also have WiFi options, so we know all of their pros and cons). 

Just by changing their password, a homeowner can break the connection. So can router firmware upgrades, changes to firewall settings, and WiFi SSID resets. Additionally, sometimes the signal quality/connection will be affected by something as simple as whether a door is open or not. So-called ‘WiFi extenders’ are no great guarantee of enhanced performance either. Who hasn’t had some important consumer appliance disconnected because someone wants to use a vacuum cleaner? (Think music system, think plug-in WiFi extender, more tragically think fish tank!)

In Wattwatchers’ experience, working directly and indirectly with large solar installation groups, it is not surprising to have 70% or more of customer support requests being attributable to WiFi connectivity issues. That’s a lot of troubleshooting, which distracts from the real business of selling, installing and maintaining more and more solar rooftops.

Other smart energy devices might connect to the router inside the home with an ethernet cable. If this cabling is not already in place, this would add significant installation hassle and expense, and can easily be pulled out, whether accidentally or intentionally. (Oops! Was that what that cable was doing? Who knew?)

Everyday WiFi unreliability can be OK if the service in question is the home’s television or console gaming choices, which we might add people are highly motivated to keep connected! But you have to ask yourself: how motivated am I going to be to maintain an always-on internet connection that allows someone – and that someone is likely to be an energy utility – to stop my solar from exporting to the grid, or even from operating at all?

Cellular definitely costs more in terms of the raw communications service costs for the SIM and data plan. In the Wattwatchers world, for example, we typically charge $5 per device per month for the full service of data and communications using our cellular devices, versus just $1 per device per month for WiFi (the 4G/3G cellular component adds $4 per device per month for the SIM and data plan).

Yet in Wattwatchers’ experience over more than six years of commercial sales, with 40,000-plus of our devices in the field, our cellular devices outsell WiFi ones by a factor of greater than 10:1 due to our customers recognising the challenges with consumer WiFi. This is across both residential and commercial sectors.

Why is this so? Because the real-life market experience is unequivocal: in practical terms cellular is far more reliable, with a lower operational cost once you take into account the additional costs of WiFi set-up at installation, and especially the cost of managing poor-performing or broken communications links.

WiFi is inherently confusing in terms of who is responsible for a loss of communications with a device in the field. Did the customer disconnect something, whether by accident or design? Did something change in the physical layout at the site that weakened signal strength and compromised the connection? Did the carrier fail? Was it an installation mistake or misadventure? Or is it an actual hardware or connectivity failure in the customer’s router or the energy management device itself?

Steps to rectify the situation are equally challenging. How do you get in touch with the customer to resolve the issue? It’s not easy to enforce an SLA (a ‘service level agreement’ in commercial terms) and minimum response times with a householder. Are you really going to sue ‘Mr and Mrs Smith’ for keeping their solar running? And what happens if the customer moves? How does the utility determine or ensure that the connection is remade with the new owners or tenants?

Cellular, by contrast, is more robust. When a cellular-communicating device with an embedded SIM is installed by an electrician, it starts communicating to the cloud as soon as the device is powered up. If the electrician finds that the signal strength on site is weak, whether before or after they install the device, they can easily add an extended range antenna while still on-site. In fact, Wattwatchers customers seeking exceptional reliability, with minimal likelihood of having to roll trucks to return to sites because of communications problems, often choose to pay a bit extra to install extended range antennas as standard kit.

Cellular is inherently reliable, and we make it better with our SIMs supporting all major carriers in Australia, providing an additional multi-carrier level of communications reliability and resilience. By integrating with smart, API-enabled SIMs, Wattwatchers gets unprecedented remote visibility of how the communications is performing, which also helps to analyse and troubleshoot site problems, through identifying or eliminating issues, and only having to return to site if all else has failed.

The new South Australian regulations were only introduced recently, on September 28th, and won’t be activated fully until after December 31st, so it’s still very early days for any testing of actual performance and reliability, including for the vital choice of communications. 

But we expect that the Australian Energy Market Operator (AEMO) and network operators like SA Power Networks will need to pay greater attention to the ‘Cellular vs WiFi’ question as the new regulatory requirements are bedded down in South Australia, and also as they spread in varying forms to other states and territories.


*FOOTNOTE: Fair enough, you might ask why does Wattwatchers even make and sell a WiFi device? (The Auditor 6W for monitoring, and its monitoring+switching derivative the Auditor 6M+3SW.)  Well, we recognise that lower upfront cost is a key issue for some of our customers. There are relevant contexts where a more robust network may be in place, for example in commercial and industrial situations where the WiFi network is professionally managed as part of plant and operations. In the case of the new South Australian regulations, the regulatory bodies are accepting WiFi as a legitimate option, in spite of its widely-known potential pitfalls. It’s true that WiFi can be a workable, lower-cost option for even moderately tech-savvy householders who self-manage their services (i.e. DIY home energy management). It’s just not a robust option for commercial and utility services in the energy management space, especially if reliability is logically a key requirement (i.e. when fast-response export limiting is required to head off grid disturbances and potential blackouts).


WANT TO LEARN MORE: See our solar export control page or email sales@wattwatchers.com.au