Batteries are Cheap, Backup power is expensive

@erik_squires 

I now understand how you're planning to wire this setup of yours. I think it will work. Mine is more manual. I use the Inverter when I want to be standalone. Then after nearly draining the battery, I then connect the batteries to a charger to fully charge it back. 

So, in your case, you want 24x7 power from the Inverter. in that case, you need a Charger sized to keep the battery "charge" at the same time feeding your devices.

you need to research how to determine this power rating necessary to accomplish this. or crudely, i will attach an amp meter between the battery and inverter when you have all your devices plug in and determine the amps drawn. then choose charger based on that. (give it some headroom) 

@joeycastillo For the sake of simplicity and cost I think in case of a long term outage I’ll manually enable the inverter.  

I just tried the inverter I already have and it’s a lot noisier than I expected, even at idle.  For now, I think I’ll go with leaving a smart charger on the batteries to keep them topped off and if we ever have a real outage I’ll hook up the inverter as needed. 

Perhaps a future me who is wealthy and can do all the other home upgrades he needs will provide an inverter upgrade. 

@dinov +1 Same here. I think it is a Cumings natural gas generator with 50A/120V = 6kW. For brownouts and the 5–10s between power out to generator auto-on, a few small APS do the job.

OP @erik_squires : Re UPCs, also consider battery degradation. At work I had a couple of Desktop PC-size UPCs (120 and 240V) to protect our scanning electron microscope mainly from brownouts. Batteries need to be replaced every 5-10 years. For one they cost, and in one case the batteries ballooned and I had to cut the case to get the batteries out. Between installation and full failure, the battery performance degrades, so if you really want to make sure your back-up lasts for the desired time, also factor in lowered battery capacity with time, or schedule regular battery swaps.

@oberoniaomnia  - That’s another thing.  The lead-acid batteries used in the common UPS does not have the lifespan of modern  LiFePO4.  

According to Gemini, I can get 5 to 15 years of service vs. 3 to 5 years with lead-acid. 

Generally, APC is still selling designs it came up with it seems 20 years ago while battery technology has really moved forward.  The one good thing is that in the US at least the lead recycling rate is high and environmental contamination low for lead acid. 

We finally installed a whole house generator 26KWa-Kohler- natural gas- a little more than a year ago. After the Texas "big freeze" in 2021, I swore I would not go through that again (or the threat of rolling blackouts during peak summer heat, which is brutal here). Since it takes the generator a bit to come fully online--arguably in the tens of seconds, though the switch over happens in milliseconds, that’s obviously enough of a time lag to disrupt Internet service. 

Since so much of what we have today is Internet dependent, including household alarms, security cameras, etc. (all with battery back ups), I bought a substantial Eaton sine wave 20 amp UPS. This way, the Internet signal is covered during the generator switch over. I’m less concerned about computer activity during a power outage than the security systems. (and fwiw, I had a pretty elaborate wiring scheme approved to avoid having my main hi-fi part of the same circuitry as the ATS for the generator; the hi-fi is not supported by the generator at all). One less thing to worry about  and--no, I would not be listening to the hi-fi during a power outage.