I would start by getting a Kill-A-Watt (or generic) so you can measure power draw (under artificial load). The price between a 600W UPS and a 1000W UPS can be dramatic. When I hear "small server" I think of an R210ii / similar platform that uses less wattage than a old fashioned light bulb.
If you’re patient and can self-support, your local non-profits and their online stores may be useful.
It’s rare to see big gear NIB, but it does happen; have seen rack mount Cyberpower, 10 outlet, hi-watt units, IOB going for around $200+ in the last 6 months. Picked up a previous generation, 5 disk NAS for a tenth of its retail price, used.
You’re north of my border so my sites won’t work for you, but seriously, look into any Goodwill/Salvation Army type organizations, and don’t neglect local, they can be rewarding too.
This is the best way, get one cheap or even free with dead batteries. Then just replace the batteries on the cheap and you've got yourself a UPS that was probably a few hundred or more $$ for the cost of maybe $100 in batteries.
Look for refurbished units, you can get enterprise grade units for like half the retail price. I recently got a refurbished APC from refurbups.com. Comes with brand new batteries, mostly rack mountable stuff. Ended up being a little over half the price of a brand new one with shipping. Can't tell at a glance if they ship to Canada, but if not I'd be surprised if there wasn't a similar Canada based site you could find.
I know it's not quite what you asked. But if you have a little DIY ability you could build a good UPS out of a 100ah LiFePO4 battery and inverter. I've seen a few youtube builds where the runtime beats out what you can get out of a regular UPS. And with less maintenance.
This is not a good idea unless you really know what you're doing. High capacity batteries and high power circuits are pretty dangerous and there's a surprising amount of complexity to build a reliable UPS. You'd probably have better luck modding an existing UPS (say from a flea market) to use a bigger battery if you are really desperate to save every dollar.
Plus making it yourself you probably won't save any money unless you already have all of the tools required, which is pretty extensive if you wanna do things right/safely.
UPS For Less: https://batteryupsforless.com/ca/en/
If you can pick it up in person in Markham, it's even cheaper. Bought a bunch of UPSes across a couple dozen years now, and replaced the batteries on many of them. Best prices I've found.
This is the kind of comment I was looking for!! Thank you good sir! I was hoping someone would have a link to a website that sells ups in Canada for a reasonable price!
I would love a suggestion for a ups that could tolerate running off my generator when the power is out for extended periods, anyone have a decently priced recommendation?
I've been running my stack with a pair of Cyberpower 1325 VA. All told I sit around 750 watts average use which with the two evenly balanced gives about 10 minutes runtime. Enough to shut things down (includes keeping the poe powered APs up to access things via laptop) with the NAS being configured that if the battery gets to 5 minutes runtime it will shut itself down in case something happens when I'm not around at least the main datastore won't abruptly crash.
Can find them for about $150 USD each if you look around. If your servers have front displays you should likely be able to see the draw from there, but like mentioned by another a 'kill-a-watt' is nice to calculate all those extra bits like a modem or switch that are less obvious amounts.
I think it's around $0.18 here last I looked. Still not nice to the bank but not bankrupting at least. Now keeping the room cool mid-summer, that's another matter...