Interesting point, I guess DIY means something different to different people. For me, DIY means anything that doesn't require a professional installer.

To your point though, I do have a couple of EG4 inverters included in the results at the upper capability end. Sounds like you'd be interested in seeing more separate inverters than just those few I currently have. Adding those isn't too difficult, I will just need to make it clear to the audience which items require additional parts to be a functioning system.

That's a good point. I'd have to think about how to design the UI in a way that doesn't add too much complexity while accommodating this kind of situation.

In practice for now its up to the user to choose their highest drawing scenario, whether that's a summer configuration or a winter one.

Since this is not a battery life calculator, the metric to track is the max continuous power draw. Even if the draw lowers after initial heating, the inverter must still be able to handle the initial ramp up.