UPS Self-Consumption

I’ve been using an APC Back-UPS Pro 550 for a long time for my home lab to avoid unnecessary data loss just because of a blowing fuse or because of a power failure.

Granted, the latter rarely happens in Germany, though it happens from time to time and when you have complex systems set up in your homelab you might suffer from this with data loss.

So anyways – this Back-UPS Pro 550 delivers about 300W of output power and with some changes in my infrastructure I am hitting this limit in certain situations and the UPS informs me by beeping and forecasting me awesome 3 minutes autonomy time. So I’ve chosen to search for a more powerful replacement.

Luckily I got my hands on a Henkelhausen HEASRT01, which is a 1000 VA rack/tower UPS with two batteries. According to the datasheet this machine should give me 900 Watts of real output which is more than enough for me just hitting the 300W mark.

Now as I bought me some Shelly Plug S lately I put one on the line to the UPS to check up on the overall consumption and turns out: The UPS alone is taking about 70-80 Watts without any load – batteries full, so no loading and when I added some load on it (UPS shows me ~150W load for my 24/7 production devices), the Shelly Plug S shows me a consumption of 230W – so still an 80W difference.

That really shocked me a lot – I thought there might be like 20W consumption on the UPS or so, but 80 is really much. I googled a little and it seems like APC UPS in the 1kVA region would consume something like that. And 60W difference is huge for a 24/7 device. At ~0,29 EUR per kWH for my renewable energy, this means more than 150 EUR/year and that’s a price where I can already get an APC UPS for.

I didn’t to this test with the Back-UPS Pro 550 so far (or maybe I did when I got it years ago and can’t remember), so I did the same setup and plugged the UPS behind another Shelly Plug S. With the battery at ~50% and without load the Back-UPS Pro 550 took 14W from the Shelly – loading the battery at this time. That’s quite affordable compared to the other one.

So I’ll check whether I can get a hold of an APC Back-UPS Pro 950VA or larger. Price comparisons show them from ~170EUR so an ROI of less than two years… I’ll keep you posted.

Update 11.01.2021

So as promised I am back with some more learnings.

First things first, I was comparing apples and oranges. So the Henkelhausen UPS is an on-line UPS, meaning it’s always powering the systems through the UPS and the battery. That’s why it needs so much power compared to the line-interactive UPS which just gives you a surge protected outlet by default and has to switch to battery mode when mains fail.

Anyways for my home use a line-interactive is good enough by far, so I got myself an used APC Smart UPS 750 from the bay for 70 EUR which gives me 500W usable power and about 12min uptime on 300W which should be enough for a proper shutdown.

I’ll post an update when I have found a proper way of shutting down my environment in the right order….

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