Wife and I have a lot of non perishables put away, but we also have 2 chest freezers.

While I have a generator, with fuel shortages coming soon, I worry about losing the frozen food if the grid goes down.

Trying to figure out with a limited budget what my options would be for some kind of deep cycle batteries to at least power the chest freezers for an hour or two once a day to keep the food safe.

Charging them primarily with house power and relying on some portable solar option as a backup.

Thanks.

My truck camper uses two Interstate Deep Cycles linked with a 110 watt solar panel with controller.  

First the Interstates, they are old school deep cycles, lead acid and you need to periodically check the fluid level.  That said, they are the preferred battery by RV and Marine applications Now to simplify this a lot, its because they handle deeper draw downs and still last up to seven years maintained.  Without an alarm, motor applications like RV/Marine tend to draw down lower.  For example, a trolling motor on a boat or like in my case heater fan, cooling fan.  

Now the solar setup, once more a simplified, its a battery maintainer and the controller keeps it from over charging and maintaining.  Normal draw down, it will charge one of my two batteries in eight hours of direct sunlight and warm temperatures so basically a half charge which on two batteries is a lot of use.  The normal model of my truck camper came with one battery but I upgraded to the Boondocker with two and the solar package because I plan to do approximately two days off grid then one on.  If I do more than two days off grid, then I need to run my generator and or truck motor.  Truck is much slower because its alternator though oversized is limited through the wires I'm hooked into.  Hooked into my tow jack, its actually not much better than my solar setup.  I'm exaggerating a bit but its not run a couple hours and I'm good to go.  Its closer to my 2500 genny needing about five hours. What temperature and how much sunlight are big deals with solar panels which is why best I can say is a maintainer when not in use really.  

If you are seeing a trend here, its best to have more than one system for maintaining and charging.  For a home application, I'd run a 110v ac battery charger maintainer something like a Battery Tender so the batteries are good to go when needed.  Fast charging at home, I use a smart charger that feeds 10 amps then trickles down to maintaining.  That way I can put a battery,  or two in my case, on charge then not have to worry about cooking it.  I do this on my truck when I run its two batteries down.  Don't ask.

Now inverters, converts DC to AC.  I've been using inverters for years upon years.  First for my boat which I only offgrid and now this camper.  The camper I'm going a two inverter approach, a 400 watt and 150 watt.  The biggest mistake people make with inverters is they get too large an inverter.  They look at their highest wattage requirement which more often than not they only use infrequent because something 1,500 watts, for an example, will drain two batteries in no time at all.  I'm talking minutes here.  What they don't take into consideration is the inverter its self requires power and bigger the inverter, the more it draws even if all you are using is very little wattage.  Learned the hard way, its much much better to size your inverter to your average application, what you are actually using for.  

Now for how long, I wish it was as simple as do the math but its not.  There's all kinds of factors.  Not only does the inverter draw current but so do the wires you use, and then there's surge wattage when motors initially kick in and even that's not as consistent as it looks on paper.  Sometimes the surge is this and sometimes its that.  Temperature and all sorts of factors factor in.  What I figure is two days on two batteries running minimal usage like a fan with periodic something else like water demand pump, lights, etc.  I would figure running a freezer at home should be about the same, a couple days safely.  Unfortunately when we need this shit, its never a nice warm sunny day.  What is true is how much you take out, you have to put back in.  

Now in case anyone is curious, this new truck camper is the cats meow compared to my boat for boondocking/off grid.  My must haves like hot water heater, fridge/freezer, and heater, typically high current demand, runs off propane.  My fridge, a Dometic 3 way, when I switch to DC, doesn't cool really but only maintains so it doesn't draw down my banks as badly.  Even the hot water heater is on demand so very little draw until needed.  The AC, of course, is only 110 but it will run on a 20 amp extension cord and my 2500 watt inverter genny.    Its way more efficient than my boat is.  

Anyway using a battery bank to power stuff is doable.  It just takes some experience with it.  I hope this helps.  

Tj