Depends on the price of batteries, which are rapidly declining. Within the next few years the numbers will change in favor of batteries. Though it also depends on the load and having enough space/sunlight for the solar array
Currently, the absolute cheapest I can find lithium batteries (I am planning a solar+grid load-balancing setup) is about $160CAD/kwh. To prepare for the worst case (i.e. minimal solar generation during and following the storm - say, middle of winter/happens to be cloudy/panels are damaged/etc) I’d need to spend over $30,000 in batteries alone to have the same capacity as $120 of gas. Not to mention the sheer amount of space that would take. And the cost of solar panels (10kW actual generation capacity, minimum, to keep essentials running), at roughly $1/W in Canada, adds another $10,000 to that estimate. And that’s not including the cost of installation, which based on what I’ve heard, probably adds another $10-20k.
While there are some interesting advances being made, I do not believe that battery capacity costs will decrease by 3-4 orders of magnitude “within the next few years,” unless you anticipate gasoline/diesel/etc prices to go parabolic. It’s very obvious why people would much rather have a generator and some Jerry cans for a few hundred bucks than a solar + battery setup that costs more than their car.
The overall point though, is that solar and/or batteries are not a viable alternative for emergency backup power, nor will they be "within the next few years." Within the next few decades, maybe.
Fair call for lithium chemistries, which will probably drop closer to one order of magnitude within 2-3 years (if the trend from the last year-to-date holds). But if we're talking about sodium ion, I wouldn't be surprised if that did drop by a couple of orders of magnitude, which is already sitting about ~140USD/kwh for consumer packs (but before shipping from China). It has a weird discharge voltage curve and needs a more capable inverter to handle it though, but at the prices I'm seeing, overcapacity is plenty affordable.
Or if you're looking now at sodium ion. It's only just hitting the consumer market, but it's already cheap enough for energy storage at the scale GP is talking about. Might take a few years for cell quality, inverter, and charging technology to improve, but by 2030 it will be so dirt cheap to the point that it would be economically sensible for any household.
I'm trying to move to a nicer house. When I do that, I'll almost certainly just go for it.
Also, no offense, but I'm not trusting a brand new energy storage technology bolted to the wall of my house. I'll businesses trial it out first for a few years.