Features → Reading your own hardware

Reading your own hardware

Your inverter knows what it is making right now. The question is how that number reaches a decision about your car — directly off your own network, or round trip through a manufacturer's cloud at whatever rate they permit.

What a slow number costs you

Five minutes, which is what most of the clouds Sunplug supports settle for, is close enough to keep up on all but the choppiest afternoons. Fifteen is a bigger gap: on a partly cloudy day, a fifteen-minute-old surplus figure is a memory rather than a measurement. The cloud that took 4 kW off your roof arrived and left inside that window, and a decision made on the old number is a decision made about weather that has already passed.

At that end, the failure is not that the car charges slightly wrong. It is that the system cannot tell the difference between "a cloud went over" and "the sun has gone", which is the distinction the whole of the waiting logic is built to make. Reading locally sidesteps the question entirely rather than answering it well.

Why local, and when the cloud instead

For most brands there genuinely is no cloud alternative and local reading is the only path. For a few, Sunplug offers both — the reasons are worth knowing, because they are not technical.

• Enphase — the licence for their current API does not permit a consumer application to do surplus tracking with it. Local reading of the gateway is not a preference here; it is the way in.
• SolarEdge — Sunplug reads their API every fifteen minutes. Offered, with the honest note that local is better.
• Fronius — Sunplug does not offer a cloud path for Fronius. Local reading is the only path today.
• Sungrow and GoodWe — the cloud works and Sunplug supports it, and it publishes at around five minutes. Offered, with the honest note that local is better.

The pattern underneath: a manufacturer's cloud publishes at whatever rate they choose to offer, and that rate is rarely the one a live decision wants most. Five minutes, and even fifteen, is enough to follow the sun across an afternoon — what it misses is a single cloud passing over, which is the gap local reading closes. Sunplug reads locally by default everywhere it can, and offers the cloud path for the households that need it in the meantime.

What the agent actually is

A small program that runs on something already switched on in your house — a NAS, a mini-PC, a Raspberry Pi. It asks your inverter the same question your manufacturer's app asks, on your own network, every thirty seconds, and passes the answer up.

It makes only outbound connections. Nothing is opened to the internet, nothing is port-forwarded, and your inverter is not exposed. If your network blocks it from reaching the hardware, it tells you that rather than silently reporting zeroes. Setting it up →

The one case where local is not better

It is worth naming, because it is the honest boundary of the argument. If your equipment can only be read through the cloud, and that cloud is fast, the local path buys you nothing except one less machine to keep running. Sunplug does not insist on the agent where the cloud genuinely answers well — the setup guides say which case each brand is, and a few of them say "either".

Stuck? Email me.