serin labsThe Best Kumo Cloud Alternative for Local Mitsubishi Control
Here's what finally did it for me. I wanted to change the temperature, and the app wanted me to sign in first. For a heat pump bolted to my own wall. Kumo Cloud isn't broken, exactly. It just kept wedging itself between me and my unit, one server round-trip at a time, and half the time it couldn't reach every setting anyway. So I cut it out and went looking for a proper Kumo Cloud alternative. Something local. Something that answers to me, not to a login screen.
This is what I landed on: a small ESP32 board, the Serin controller, that clips onto the CN105 port already sitting inside most Mitsubishi indoor units. It runs open-source firmware, talks to the heat pump directly, and keeps every command on your own network. No account. No cloud. Nothing to pay each month. Setup is about a coffee break long, and you never see the Kumo Cloud login again.
Why People Ditch Kumo Cloud
Kumo Cloud does the basic job. Set a temperature, pick a mode, done. To be fair, that's most of what anyone needs on a Tuesday.
The problem isn't the app. It's the cloud attached to it. You need a Mitsubishi account. Setup and away-from-home control lean on Mitsubishi's servers, so your thermostat rides on someone else's uptime and someone else's roadmap. Your usage data leaves the house. And the day Mitsubishi changes the app, retires a feature, or drops an older adapter, you go along whether you like it or not.
None of that is a scandal. It's just what "cloud" means. But this is a machine you touch every day, in your own home, and a lot of people would rather not have a middleman standing in the doorway. I'm one of them.
What the Local Alternative Actually Is
The Serin controller is a pre-assembled ESP32 board with a cable that clips onto the CN105 port inside the indoor unit. Once it's in, your mini-split becomes a normal device on your Wi-Fi. Control it from your phone, from a browser, or from your smart home platform. All of it stays on your LAN.
You flash it from your browser over USB. No soldering, nothing to compile. There are two firmware options, and you pick based on the smart home you already live in. Both are fully local. Both are free and open source. More on the choice below.
Kumo Cloud vs. Running It Locally
| Kumo Cloud | Serin controller (local) | |
|---|---|---|
| Account required | Yes, a Mitsubishi account | None |
| Internet needed | Yes, for setup and away-from-home control | No, control runs on your LAN |
| Where your data goes | Mitsubishi's cloud servers | Stays on your home network |
| Remote access | Built in, through the cloud | Through Home Assistant or an Apple Home Hub |
| Home Assistant | Not officially supported | Native, via ESPHome |
| Apple Home + Siri | No | Yes, with the Apple Home compatible firmware |
| Unit diagnostics | Limited | Compressor frequency, error codes, and live logs in the web UI |
| Ongoing cost | Free app, tied to the cloud | No fees, no cloud |
| How it connects | Mitsubishi's Wi-Fi adapter | CN105 serial port |
Will It Work on Your Unit?
Everything hinges on one port. The Serin controller connects to the CN105 serial port, which is built into most Mitsubishi Electric indoor units. Confirm yours has it before you buy anything, and the rest is easy.
The quick proxy: if your unit runs on Kumo Cloud today (or MELCloud in Europe), that's a reliable sign it has a CN105 port and will work here. Still, take five minutes and confirm your unit has CN105 for certain. It's the difference between a clean swap and ordering hardware for a unit that can't use it.
Two Ways to Run It Locally
Which firmware you flash comes down to one thing: where you want to control the heat pump from. It's a big enough question that I wrote a full ESPHome vs Apple Home comparison. The short version:
- You run Home Assistant, or want to. Flash ESPHome. Your mini-split shows up as a native climate entity, and every HA automation applies. Start with the ESPHome setup guide.
- You're an Apple household with no server ambitions. Flash the Apple Home compatible firmware. It pairs straight into the Apple Home app, Siri works, and there's no hub in the middle on your home Wi-Fi. Start with the Apple Home setup guide.
Both do everything Kumo Cloud did, and then some. One heads-up: the Apple Home firmware isn't MFi-certified, so the Home app will ask you to tap "Add Anyway" when you pair it. That prompt is expected. The device works normally right after.
What You Keep, and What You Gain
Leaving Kumo Cloud doesn't mean giving up the conveniences. It mostly means getting them without the cloud tax.
Remote access still works. With ESPHome it rides on however you already reach Home Assistant from outside the house. With the Apple Home firmware it goes through an Apple Home Hub, an Apple TV or a HomePod. On your home Wi-Fi you need nothing extra at all.
Scheduling still works. You lose Kumo Cloud's built-in scheduler, but you gain your platform's. Home Assistant automations, or Apple Home schedules and scenes. Both leave a basic app timer in the dust once you get going.
You finally see the unit. The built-in web UI shows what the factory app never did: compressor frequency, outside air temperature, runtime, error codes, live logs. Phone off, hub unplugged, doesn't matter. Open the controller's IP in a browser and drive the heat pump directly.
A real room sensor, if you want one. A mini-split reads temperature up at the indoor unit, near the ceiling, where the air runs a few degrees warmer than where you actually sit. Both firmwares can regulate off a sensor placed at seating height instead: any Home Assistant sensor on the ESPHome side, or an inexpensive BLE thermometer on the Apple Home side. It was the single biggest comfort upgrade I made. Kumo Cloud has no equivalent.
What About MELCloud?
Outside North America your app is MELCloud, not Kumo Cloud. Same story. Same manufacturer, same account-and-cloud model, same cloud dependency. The Serin controller doesn't care which region your unit shipped to; it talks to CN105 the same way regardless. Everything on this page applies whether you're walking away from Kumo Cloud or MELCloud. If your unit runs on either one today, it has the port you need.
Is It a Drop-In Replacement?
No, and I'd rather be straight about it. Kumo Cloud is install-an-app easy. Going local asks a little more: order the board and cable, pop the indoor unit's cover, clip the cable onto CN105, then flash the firmware from your browser and join it to Wi-Fi. Call it a coffee's worth of setup, not thirty seconds.
What you get back is a heat pump that answers to you and nobody else. No account. No server outage that leaves you unable to change the temperature. No quiet worry about what happens to the app three years from now. Once it's set up, there's nothing to maintain and nothing to renew.
And if you catch the Home Assistant bug later, you can reflash from Apple Home to ESPHome, or the other way, any time. Same browser tool, no rewiring. I put the Apple Home firmware on my parents' units for exactly this reason: I wasn't about to stand up a server in their house or turn myself into the family sysadmin. They already had iPhones. Scan a QR code, walk away. That's the part Kumo Cloud can't match. It's your hardware, and you decide how it runs.
The Verdict
If you want out of Kumo Cloud, go local. It's the cleaner setup and it's the one you actually own. Here's the path:
- Check that your unit has a CN105 port. If it runs on Kumo Cloud or MELCloud today, it almost certainly does.
- Get the board and cable, one per indoor unit.
- Flash the firmware from your browser. ESPHome for Home Assistant, or the Apple Home compatible build for Apple households.
That's the whole thing. Same heat pump, same comfort, without the account or the cloud sitting in between.