Inverters not needed.
I will apologise upfront for a long-winded post. I do know how this stuff works and would like to help, so bear with me
IMHO inverters are still generally less cost-efficient and not the way to go. I have been totally solar for several years and still see no need to get an inverter. My batteries have lasted much longer than friends who went the inverter route.
There are plenty of very efficient 12VDC/24VDC compressor fridges out there. You can even build your own insulated fridge-freezer 'box' and fit one of these to it; this is how it's done on boats! Google them for US sources.
Products - Danfoss
See here for application notes and technical info:
Products - Danfoss Technical
select Direct Current Compressors link, and see the Literature tab.
I have a 240 litre Waeco fridge-freezer (using a Danfoss BD50F compressor) that auto senses the voltage source it is connected to and switches to the 'dominant' source automatically. Eg. normal mode of operation is 12VDC from solar panels. From time to time I give them a rest and manually switch to my BOV's 24VDC 'start batteries' while driving.
If I am somewhere with mains power (240VAC), plugging the lead in causes the fridge to switch to mains. Also, if I start the generator, it also kicks over to 240VAC. This setup requires a small relatively inexpensive add on sensor and rectifier box from Mobitronics ( https://www.compass24.com/watersports/abnetshop.pl?nummernliste=563595
) to rectify the applied mains voltage source.
This might sound complicated , but it's not at all! It's also more efficient than using an inverter. I would only use an inverter if there was no option but to have a mains powered appliance, because they will shorten your battery life as well.
Things that make a difference to your solar setup:
the current (Amps) your fridge draws at startup, and when running; The number of times per day your fridge compressor cuts in; the length of time it runs when it cuts in; your batteries (number, voltage, configuration); panels (number and wattage); hours of direct sunlight per day; Solar charge controller etc. These all need to be worked out. Luckily there are on-line tools and calculators to help:
This company has some examples of load calculation sheets etc
Where to start:
Read everything you can lay your hands on about solar. Here's the location for best books I've found so far. Collyn Rivers is an Engineer with many many years experience. Truly you can't go wrong with these books.
Here's a review of solar system buying on ebay:
eBay Australia Guides - Buying solar panels and alternative energy on eBay
Work out which fridge you will use (110VAC + inverter or 12/24VDC). Work out what the 'power debt' is that your batteries and solar system will have to supply (and recharge daily).
Remember that fridges draw more current on startup (for approx. 30 secs) then settle down to a lesser draw. Your battery system and charging system must be able to cope with this. For example, my fridge draws 9.0A at startup and drops back to about 4A running.
Here's a review of Inverter + mains power fridge versus 12VDC fridge. Remember the DC fridge is more expensive to buy, but you can convert a mains fridge to 12VDC at a lesser cost. Don't worry about the Motorhome references, just read 'BOL' instead.
READ the next link, if nothing else!
See also: http://www.fridge-and-solar.net/info.htm
My Waeco fridge uses a 12VDC / 24VDC Danfoss BD50F compressor. There is also a lesser power BD35F model. Here's the beauty of it - you can buy the compressors separately and convert your existing 110 VAC / 240VAC fridge-freezer.
Many marine installations use these compressors because they suit custom-made fridge applications. Here's a couple of links to get you started. Also, all Waeco mini-fridges for camping / vehicles use these compressors as well.
http://www.ra.danfoss.com/Technical...Article/author_1/RAC Compressors Oct 2005.pdf
It is also more efficient to run off 24VDC than 12VDC (Ohms Law > P=iv, twice the voltage means half the current draw), so you might even consider having a totally 24 Volt system. But a lot of solar systems are geared to 12VDC operation. A 24V system will likely cost significantly more to setup.
Please don't let all this scare you off. Let me know if I can help in any way. Good Luck with it, Herne
P.S. My solar system is as follows: 2 x 80Watt BP Unisolar amorphous silicon panels, a BP Solar PL-20 Regulator, 4 x Trojan T105 Deep Cycle Battery 6V
225Ah (wired in series-parallel to give 12 VDC output).