We put a plug-in solar kit on an Irvine balcony. Here's what we're measuring

Why bother

There's a lot of balcony solar content on the internet and almost none of it is based on anyone's actual panel. It's manufacturer specifications restated, or model output presented as fact, or German figures applied to California without adjustment.

We'd rather not add to that. So: one kit, one balcony, one logger, and a public prediction made before the data comes in.

The setup

What our model predicts

Before any data, here's the shape of what our methodology page says a balcony like this should do:

1,586 kWh/kW/yr × kW × direction factor × tilt factor × shade factor = annual kWh

The specific numbers go up alongside the kit specification, and they're written down before the first month's readings so we can't quietly revise them later.

What we're measuring

Daily production, which is the headline.

Production against forecast weather, so we can separate "the model is wrong" from "it was cloudy in June."

Self-consumption, which is the harder and more interesting one. Producing 4 kilowatt-hours means nothing if the flat is empty and 2 of them go to the grid for free. We're logging household draw alongside production to work out what share is actually used.

The tilt experiment. At some point we'll run the same panel vertical on the railing for a month and tilted for a month, in comparable conditions, to test the 0.62 factor we've been quoting. If that number is wrong, a lot of our advice about tilt brackets is wrong with it.

Seasonal spread. December production in California is roughly half of June's. Anyone quoting an annual figure from a summer month is overstating by a wide margin, and we want the real curve.

What we'll publish

A monthly update with the numbers, and a proper comparison at twelve months.

Specifically, we'll publish the gap between prediction and reality, whichever direction it runs. If the model overstates by 20 percent, that's the most useful thing we could tell you, and we'll change the model and say what changed.

What this can't tell you

One balcony. One orientation. One year of weather. It'll tell you whether our model is roughly calibrated for a west-facing Irvine balcony, and it won't tell you what happens on a shaded east-facing one in Fresno.

That's the honest limit of first-hand testing by one person, and we'd rather say it than imply this is a study.

If you have one

If you've got a plug-in system running anywhere in California, we'd like your numbers — kit, orientation, tilt, and monthly kilowatt-hours. A dozen real installations would be worth more than our one, and we'd publish the aggregate with the model comparison.