MIDEA HEC2 6kW Hybrid Solar Inverter with 10.2kWh Battery, On Grid or Off Grid

Add up everything that will run at the same time, in watts, then size for the startup surge on top rather than the running figure. Anything with a motor or a compressor, a fridge, a pump, a washing machine, a power tool, pulls far more for the first second than it does once it is turning.

Our inverters carry a surge rating as well as a continuous one, and it is on the spec table above. The high frequency models hold roughly twice their continuous rating for a moment. The low frequency transformer models hold three times, which is why they cost more and weigh more, and it is the reason to buy one.

If you are not sure what your gear adds up to, tell us what you are running and we will size it for you.

Buy pure sine. Modified sine wave is a square approximation of mains power, and the list of things that dislike it is longer than the list that does not: anything with a motor speed controller, most microwaves, laser printers, CPAP machines, battery chargers, and anything with a transformer in it, which will run hot. Common symptoms are insufficient power output, wrong speed of operation, components wear out faster.

It is also where the buzzing comes from. Audio gear picks up the stepped waveform as a hum. On pure sine it does not.

Everything we sell is pure sine wave. That is deliberate, not a range gap.

An inverter charger is an inverter with an AC battery charger built into the same box. Plug it into mains or a generator and it charges the bank. Lose the mains and it inverts from the bank instead, so the load never notices.

You want one if the system has mains available some of the time: a bach on an unreliable line, a caravan that gets plugged in at a camp, a workshop, a house with an off-grid backup. You do not need one if the bank is only ever charged from solar or from the vehicle, because then you are paying for a mains charger you will never plug in.

On our inverter charger models, yes. They have an MPPT solar charge controller built in alongside the mains charger, so one box does the inverting, the mains charging and the solar charging, and the three of them share one set of settings instead of arguing with each other.

The controller size and the maximum solar array voltage are on the spec table above. Those two numbers decide how many panels you can put on it, so check them against the array you have in mind before you buy.

Our plain inverters have no solar controller. Those need a separate one.

The higher the system voltage, the less current for the same power, and current is what costs you money in cable and what turns into heat.

A 2000W load on 12V pulls about 185 amps out of the battery. The same load on 24V pulls 93. That is the difference between 70 mm2 cable and 25 mm2, over the same run.

So: 12V for small mobile systems and where the vehicle is already 12V. 24V once you are past about 2000W. 48V for house sized systems and anything over about 5000W. If you are building from scratch and the load is real, start at 24V.

Size the cable with our DC voltage drop calculator

A deep cycle battery, not a starter battery. A starter battery is built to give a few hundred amps for three seconds and then be refilled immediately. Run an inverter off one and you will kill it in weeks.

For size, work from the runtime you want, not from the inverter's rating. Watts times hours, divided by the system voltage, gives you the amp hours you will pull out. Then decide how deep you are willing to go on that bank, which sets the size.

The inverter also has a minimum bank size, because a big inverter on a small bank will pull the voltage down and trip itself on its own load. Tell us the inverter and the runtime and we will size the bank.

Only the small ones. A cigarette lighter circuit is usually fused at 10 or 15 amps, which is about 120 to 180 watts before the fuse goes, so anything above a 150W continuous load has to be wired to the battery directly with its own fuse.

That catches people out, because a 300W inverter with a lighter plug on it could still trip the fuse if run at high loading long enough.

And if the engine is off, watch the starter battery. It holds far less usable energy than people expect and it does not like being run down.

Nearly always one of three things, and only one of them is the inverter.

Low battery. The alarm sounds when the DC side falls below about 11V on a 12V system, and it shuts down shortly after to save the battery from itself. That is the inverter protecting you, not failing.

Voltage drop in the cable. If the cable between battery and inverter is too small or too long, the inverter sees a low voltage that the battery does not actually have due to losses, and trips out on a battery that is half full.

Startup surge. The label figure is the running figure. See the first question.

Check your run with our DC voltage drop calculator

Yes, with the right size, and a microwave is the one people get wrong.

The wattage on the front of a microwave can sometimes be its cooking power, not what it draws. Consumption could be significantly above that. Read the plate on the back, then size for at least twice that figure.

A kettle or a jug is simpler and more brutal: it is a straight resistive load, it draws its full rating the whole time it is on, and 2,400W is 2,400W. It will run, but on a battery system it could be an expensive cup of tea.

Indoors, dry, out of direct sun, with air around it, and as close to the battery as you can practically get it.

Close to the battery matters more than people think, because that is the cable carrying the big current. Every extra metre is voltage lost and heat made. It is almost always cheaper to move the inverter than to buy the next size up in cable.

Not in the engine bay, not where it can get wet, not sealed in a locker with no ventilation. They are not weatherproof, and heat is what shortens their life.