Top tip 01 · Connectivity
Get the kit online, and keep it online
Five ways to connect a solar or battery system to the internet, ranked worst to best by how they fail. The ranking matters more than the list: the difference between a hardwired connection and a powerline adapter is not speed, it is whether the system is still online in a year.
From our founderTim Gauntlett TMIET
The connection is part of the install
A system that is not connected is not finished. It will make power, and it will do it blind — nobody can see what it did yesterday, nothing can be diagnosed without a site visit, and the first anyone knows about a fault is a bill that looks wrong.
So treat the data connection the way you treat the AC side: something you specify before you go, commission on the day, and hand over working. Not something you mention on the doorstep and leave with the customer to sort out.
There are five ways to do it. They are not equivalent, and the order below is the whole tip.
- 1Hardwired ethernetRouter to device on CAT5. Nothing to drop, nothing to re-authenticate.
- 2Wi-Fi bridgeWireless across the building, wired for the last hop into the device.
- 3Wi-Fi to the deviceWorks on the day. Survives until the router or the password changes.
- 4Powerline adapterCommissions fine, then drifts. The failure arrives after you have left.
- 5No connectionOptional on PV. On storage, many warranties require it — check the terms.
Hardwired ethernet — the first choice
A hardwired CAT5 run from the router to the device. It is first because it has the fewest things that can change underneath it: no radio, no password, no channel, no neighbour's new mesh system to contend with.
It is worth being precise about the vocabulary here, because these four words get used interchangeably on site and only one of them does what people assume:
- Modem
- Connects the building to the internet. In a domestic property it is almost always inside the same box as the router.
- Router
- The device at the centre of the local network. Hands out addresses and decides what goes where.
- Switch
- Turns one ethernet drop into several, properly. Each port gets its own connection.
- Splitter (without a switch)
- Not a switch. It divides the pairs in one cable between two sockets — which is a cabling trick, not a network. Two devices plugged into one are not two devices on the network.
If you need a second device on one drop, that is a switch. They cost very little and they end the argument.
Wi-Fi bridge — the second choice
Where a cable genuinely cannot be run the length of the building, the next best thing is to make the wireless hop somewhere you control, and keep the last hop wired: Wi-Fi across the building, then LAN into the device.
This is better than talking to the device over Wi-Fi directly for a reason that has nothing to do with signal strength. The bridge is a mains-powered box you chose, you configured, and you can stand in front of with a laptop. The inverter's own radio is none of those things.
You have also moved the fragile part of the link somewhere a fault is visible. A bridge that drops has lights on it. An inverter that has quietly fallen off the network does not.
Wi-Fi to the device — and where it goes wrong
Connecting the device straight to the house Wi-Fi is the path of least resistance on the day, and it is where most of the offline systems in the country came from. Three things work against it.
Most green tech is 2.4 GHz only — not 5 GHz. The radios in inverters, battery gateways and monitoring dongles are cheap, low-power and single-band. On a modern router presenting one network name across both bands, this is a coin toss the installer cannot see the result of.
Routers get replaced and passwords change. Not often — every few years. But when it happens nobody thinks about the inverter in the garage, because nothing in the house is telling them to.
And that is the real problem: the connection is not visible. The kit goes offline and keeps working, so there is no symptom to notice. Six months later somebody wants a year of data and it is not there.
Powerline — the last resort
Powerline adapters carry data over the mains wiring, and on paper they solve exactly this problem — a link to somewhere you could not run a cable, with no radio involved.
The catch is in the manufacturers' own instructions. Most powerline adapters stipulate that both ends should be on the same circuit — and on a renewable installation that is rarely practicable, because the whole point of the run is to reach equipment that is deliberately on its own way.
What follows is the worst failure shape there is. The link comes up on the bench, comes up at commissioning, passes the handover — and then drifts, because it is working outside the conditions it was specified for. The problem arrives weeks after the van has gone, and it looks like an equipment fault rather than a cabling decision.
No connection — what it costs
Sometimes there is genuinely no way to connect, and it is worth being straight about what that means rather than pretending it is a neutral choice.
On PV alone, an internet connection is often optional. You lose the monitoring and the ability to diagnose anything remotely, but the array will do its job.
On storage it is usually not optional. Many battery manufacturers make the warranty conditional on the system remaining reachable for remote monitoring and firmware updates — so an unconnected BESS can be an uncovered BESS. Check the specific warranty terms before you decide the connection is a nice-to-have, because that is the document that will be quoted back at you.
The other half of it is commercial rather than technical. Connecting devices is a good way to add value.A connected system is one you can support, tune, report on and come back to. An unconnected one is a box in somebody's garage that you will never hear about again — until you do.
Field notes, and a starting point for a conversation — not a design authority. The current edition of BS 7671, your DNO's own requirements and the equipment manufacturer's instructions all outrank anything on this page.