"Since that time, I’ve learned that small heaters (like coffee makers or kettles) can be kryptonite to an inverter, and that this is common folk knowledge among solar installers."
Is there any more on this? It can understand inductive loads maybe challenging inverters but resistive loads should be easy? Is it an issue of cheap inverter design, or something more fundamental?
It’s funny, power use can be really unintuitive. Try convincing someone that using the big air conditioner for heating is more efficient than using that little plug-in bar heater. Or yeah, a power board with 8 tiny wattage wall-warts isn’t using a lot of power.
I could probably run my big fridge overnight off my portable battery generator, but it wouldn’t run my small electric kettle without putting it into a special mode and for nowhere near as long.
You can definitely get equipment that can do symmetrical input/output, but if you actually model out the supply and demand curves on the system it's not usually going to be worth the extra up front expense since peak input is a small portion of the day and that extra hardware will mostly sit idle.
For that matter people often design systems where peak input can't even be accepted by the inverter and the extra power is just wasted, because it's more valuable to have a steady input over a long period than to maximize the daily peak.
I think it's partially that people want to spend less money and undersize their inverter setup. The average end user non technical consumer (maybe a person buying an off grid PV system from an installer) may not fully understand what 1500W really is, and that something as boring as a $35 tiny space heater that sits on the floor can be a 1500W load.
People will be really surprised if you tell them that their tiny floor space heater uses the same amount of energy as charging twenty high performance laptops simultaneously.
It takes just a few high wattage single item electrical things to totally screw up the electrical load budget of a site, if somebody has something like a single 8000W rated inverter.
If you want to use electric space heaters and kettles and hairy dryers and hair curlers and such, along with the other regular daily load items of a house, you're looking at a setup with multiple 6000-8000W inverters in parallel with each other and synchronizing their output waveforms. Not many people want to spend the sort of money that'll get them 3 x 8000W inverters in parallel with each other all properly installed in an electrical room next to the PV stuff, breaker panels, etc.
As an extreme example, a tungsten filament in a lightbulb would rise to 1500C (2700F) which with even a small temperature coefficient can mean inrush current 10x higher than the operating current.
