The Math Behind Net Zero: How We Calculate Our Energy Production

We talk about 74 kilowatt hours on a peak day, $696.41 in annual credits, and 33 panels. But what do those numbers mean and how do we know them? The energy accounting behind a net zero home is worth understanding — not because it's complicated, but because it makes the whole concept concrete.

A kilowatt hour is the basic unit of electrical energy: one kilowatt of power used or generated continuously for one hour. Your utility bill is measured in kWh. Your solar app shows production in kWh. When we say our house generated 74 kWh in a single day, we mean our 33 panels collectively produced 74 kilowatt hours of electricity from sunrise to sunset.

We track our production through two sources: the Tesla Powerwall app, which shows real-time energy flow, and our monthly utility statements, which show the net metered result. On any given day, the Powerwall app shows exactly how much the panels generated, how much the house consumed, how much went into the battery, and how much was exported to the grid. It's complete, real-time energy accounting.

The net zero calculation is annual, not monthly. Averaging daily production over a full year, accounting for seasonal variation, and comparing it to annual consumption gives you the net result. In our case, April 2025 through March 2026, we generated meaningfully more than we consumed in eleven of twelve months. The annual net was $696.41 in our favor.

This energy transparency is one of the genuinely enjoyable aspects of net zero living. You know exactly where your energy comes from and how much your house makes or uses at any moment. On our home tours, we pull up the app and walk visitors through exactly what it shows. The numbers make the concept real.