>>>The reviews of APC Backup-UPS 600VA vary from "junk" to "works excellent".
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>>>What do you use and are you happy?
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>>I've had a few APC units over the years. At the moment I have a Back-UPS CS 500 backing up my cable modem and router.
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>>One thing about APC is they offer runtime graphs for their products e.g. http://www.apc.com/products/runtimegraph/runtime_graph.cfm?base_sku=BK500&chartSize=large . IME the graph is a bit optimistic, my modem plus router pull less than 50 watts but the last time I had an extended outage I think I only got about an hour out of the UPS.
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>>The vast majority of UPSs use sealed gel-cell lead-acid batteries. There are only a few different sizes of these batteries. One thing you often see is a maker will offer 3 different models, say, 400, 500 and 600VA. They all use the same battery so they all store the same amount of energy. The higher VA models have upgraded circuitry so they can support higher loads (for shorter periods) if necessary, but they don't offer longer runtime at low loads.
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>>Looking at the APC runtime graph, you see that the load does not go below about 30 watts. This is the power used by the UPS's inverter to convert the DC battery to 120VAC output. So even if you have nothing plugged into it, it will not last longer than about 100 minutes, and my real-life experience with a modem and router is about an hour, tops.
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>>That holds true for just about all consumer UPSs under 750VA or so. They have only one battery and maximum runtime is usually much less than 2 hours.
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>>Larger capacity units use 2 or more batteries and offer longer runtimes at low loads, but are a lot more expensive. If you want to know if units use more than 1 battery, look for the tech specs e.g. http://www.apc.com/shop/ca/en/products/APC-Back-UPS-500-beige/P-BK500 : my unit uses the RBC2 model battery, quantity 1.
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>>In my area extended power outages are uncommon, but if they happen they're often 4 hours or more. Most outages or other issues are well under an hour, so my unit can bridge them. No size of UPS would bridge the longer outages so I just accept that when they happen I lose service.
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>>It's worth pointing out that extended/widespread outages may include your ISP's facilities, either in your neighbourhood (e.g. those grey metal boxes you see on concrete pads) or their central office. Some of those may be backed up with their own UPSs or generator, but you have no way to know. If those lose power, you lose service, regardless of how much runtime you have in your local UPS.
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>>UPSs are also useful protecting against brief brownouts or spikes/surges, and can extend the life of connected equipment by isolating them from those issues.
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>IMO the next step should not be a stronger UPS - it should be a small generator, which can give you several H if you depend on working from there. Over here we had 2 outages last year in our and parallell street, each over 6H, due to cable work. Cheap me picked up laptop, tablets, Qi loader and a bottle of champagne, called to make certain at other place current was available and went there - that option not always an answer, but there are hotels and restaurants you can go to if deadlines are looming ;-)

My next door neighbor had a generator installed at his house (at the tag of about $10,000, this is US-comma, not European comma :)). A couple of weeks ago we had a power outage. So my wife and I decided to take a walk and as soon as we left the house we heard the sound of his generator. To me this is an overkill, unless you are running a hospital or a critical care facility.
I hear that Tesla is working on a battery type generator for residential use (not solar) and it will be considerably less expensive than the generator similar to the one my neighbor had installed (gas fired). Then, maybe I will get on.
For now a UPS for 1-2 hours will do.