Before you scare sharkiee00 off, Diysolar123, let's refine some of those assumptions. I recently got a Kill-A-Watt so at least some of these numbers are fresh.
- My regular sized house has about 81W of baseline load from internet router, leakage currents, random AC/DC stuff plugged in, Nest cameras, etc.
- My 10 year old refrigerator uses 151W while running and runs about half the time (1.8kWh/day, as measured last week; it's probably a bit more in the summer).
- My 12,000 BTU window AC is rated for 980W, and I haven't measured it yet but I think steady state it will be more like 750W. It also has en Eco mode I could use if I desired to save some watts.
- A new chest freezer like
this one uses 250kWh/year (per EnergyStar estimate) or 28.5W on average; so it's probably about 114W while running if it runs a quarter of the time.
On anything with motors like this: yes there is surge current but it's unlikely 1-2 seconds of surge would align for multiple devices at the same time, and you could furthermore offset them with a simple timer switch more easily than you could by planning for overlapping surge currents for everything you own. For example: switch your two chest freezers on and off 50%/50% of the time so they don't overlap on 30 minute intervals; they'll stay cold enough, and you can check this with thermometers for a hundredth of the cost of a bigger battery. You could get way more elaborate than that with timing and not have to plan for multiple surge currents to occur simultaenously. Just imagine if the whole grid was planned for worst case simultaneously load...it would be 10x the size it actually is (and yes, I made up the number 10x, but you get the point).
More details added later:
So let's ignore surge current as that only applies to your inverter size (and wire), and OP won't be limited by battery current in all likelihood. Then it's all about battery capacity to not run out of electrons, and having enough solar panels to produce enough energy on average.
- Let's assume the government (EnergyStar) is right and the freezers use ~30W on average, so that's 60W continuously for two of them = 1.44kWh/day
- The AC is a big one: let's say 500W for 4 hours a day = 2kWh/day during the summer when you would actually use it.
- Charging your tools rounds to zero, by comparison. What do you have a couple Makita cordless drills or something? That's negligible.
So that adds up to 3.44kWh/day. If you live somewhere with 4 hours of insolation per day, that's a 860W PV system for your average load, which is roughly 4 210W "RV" panels, or 3 290W "house sized" panels. This is totally reasonable on a shed, I think. An example would be 3x 350W "house sized" panels, which are roughly 2 square meters, or roughly 6.5' x 10' for 3 of them, perfect for your shed if it's sunny and you angle them south.
For the battery, let's say you want 1 day of energy usage stored up so your frozen food doesn't thaw if it's cloudy all day (not sure if that is enough; consult other forum posts to check, but since you'll also generate some power during that time and you won't use the A/C during those days, I'm assuming). That's 3.44kWh, which is a 24V 150Ah battery. This isn't nothing, but it's also not that big and you can buy it off the shelf ready to use.
Some other thoughts:
- your AC is the biggest consumption in these assumptions. So if you're running low on battery, just sweat it out rather than thaw your frozen food. In the summer when you would be using AC it would also be sunnier / longer days so 4 hours of sun may be 6 hours of sun depending on where you live
- you could find more efficient freezers. Maybe one big one uses less energy than two small ones, if it's new. Don't open the lid very often and you'll save more energy
