There is a local guy selling an 18kVA UPS so I may just say "Screw it" and go that route. That thing could power my machine for like 15 minutes at full tilt during a blackout and completely isolates the input and output through double-conversion. We used these on scientific instruments in my past life where inductive loads in the building were frying sensitive equipment.
That sucker weighs 1400lb with the batteries!
Small ones can be that light, yes. Some are also ugly as sin on their synthetic Sine-wave outputs to BE that light as well.
Dominant Carrier Global TELCO pensioner here. (C&W, and "nailed up" - government and Fortune 400, mostly..)
Need I say more?
Well.. "maybe".
Here's a "rule of thumb" lotta folk are not aware of.
Take my gen set. A NATO/OTAN surplus Fermont-integrated rig, the MEP-803A utilizes a Marathon head switch-selectable as to 120 or 240 single-phase or 208 Wye 3-phase I can throttle up to 220 Wye, leg-to-leg, given leg-to-neutral ain't even used, ergo "so what" it is over-volted.
A Lister-Petter/Cummins-Onan 4-banger liquid-cooled Diesel of about 12 or 14 normally-aspirated HP earns a 10 KVA rating at 8,000 feet above mean sea level.
The bottom line is generally considered a 12 KVA at my 356 ft AMSL, and known to be able to stand up easily to 15 KVA peak loading.
Where "stand up" does NOT mean there is no sag when a heavy load comes online, nor any shortage of overshoot when it drops-off.
Not even
close to as stable as a major-utility power grid, distributed small and "local" or not. "Broader Shoulders" up the backline of it.
So.. run a 10 HP load? Well. "Sort-of".
I'm "all manual", and one pair of hands and eyes, so one machine at a go. Also max one motor load is only 7.5 HP. Bogging down to start? No Big deal. So all that works "well
enough".
Thing is, few are aware it really needs a factor of TEN - around 60 or 70 KVA - to run
more demanding loads.
Such as a "roughly" 10 HP CNC machine tool and its complexity.
Stability under rapidly changing load thing, yah?
Similar strictures apply to your proposed but "nominal" 18 KVA UPS.
It probably won't be stout enough to do what you think it will.
Not for machine-tools that have BOTH of gnarly motive power demands AND finicky "brains", anyway.
And batteries? Talk about a pain in the ass!
Had to keep HSBC, MoD, DoD online yah, yah JF "Deal Wit Dat".
Here? Power is out? See to it the steaks stay frozen, residence is comfy, any season of the year, and otherwise JF go do sumthin' else, is all.
Costs too much to make chips "regardless"? Just take a break and do not.
Can't pay the bills yah hafta make so great an investment yer actually SUBSIDIZING 'em, can yah?
Remember - I'm a for-the-fun-of-f**king-around sorta half-vast "Redneck R&D lab".
Not a bizness.
See Kalifornios relocating to less flammable locations with more reliable mains power. ELSE go on the dole - and still be short-served, even hungry.