A Battery And A Fridge Don't Speak The Same Language
Here's a strange fact. The power coming out of your battery can't run your fridge.
They use different kinds of electricity. The battery makes DC (direct current). Your fridge wants AC (alternating current). It's like one of them speaks English and the other speaks Japanese.
That's why every off-grid setup needs an inverter.
An inverter is a translator box. It takes the battery's DC and changes it into the AC your house understands. Plug your TV in, it just works. The TV doesn't know or care that the power started life in a battery.
The Main Kinds Of Inverter
There are a few flavors. Each one is good at a different job.
String inverters are the basic kind. One box, all your solar panels feeding into it. Cheap, and easy to fix because everything is in one place. Downside: if one panel is shaded, the whole string slows down, like a school bus going at the speed of the slowest kid.
Microinverters flip that around. Each solar panel gets its own tiny inverter on the back. Now if one panel is shaded, the others don't care. They each do their own thing. Better performance, but more parts to install and pay for.
Hybrid inverters are the ones most off-grid homes use. They handle solar AND batteries AND the grid (if you're still connected). One box does it all. If the grid goes down, a hybrid inverter can switch to battery power automatically. Lights stay on.
For a true off-grid build, the hybrid is usually the answer.
How Big An Inverter Do You Need?
This is the part people get wrong all the time. Buy one too small, the fridge won't start. Buy one too big, you waste money.
The trick is to think about what runs at the same time.
Think of every appliance in your house that might be on at once. The fridge (500W). The TV (200W). A few lights (100W). A laptop (50W). Add them up. That's about 850W.
Now add 25% on top, because some things (like fridge motors) spike when they first turn on. That gets you to about 1100W.
That's the inverter size you need.
→ Use the cable calculator to size your wiring
Pure Sine Wave Or Modified Sine Wave?
Don't worry about the words. Just remember the rule.
Pure sine wave makes the smooth, clean power your appliances actually want. Costs more. Worth it.
Modified sine wave is the cheap kind. The power looks more like stairs than a smooth wave. Some appliances run fine on it. Others (anything with a motor, anything sensitive like medical gear) buzz, run hot, or break.
For a real off-grid home, get pure sine wave. It's not worth saving fifty euros and frying a fridge.
Why The Translator Is The Heart Of The System
Without the inverter, your solar panels and your battery have nowhere to send their power. It's the bridge between everything that makes electricity and everything that uses it.
That's also why it's the part most likely to give you trouble. If something in your setup acts weird, the inverter is usually the first thing to check.
→ Read more about charge controllers
