Zero Energy Home: Happy Zero Day!

Dan CripeZero Day: October 21, 2011 is the one year anniversary of the day that Oncor (our electric grid operator) installed our bidirectional electric meter. We had been enjoying some of the benefits of our solar electric generation, but on that day, the meter let us see how much energy we were sending back to the grid as well as the amount of energy we were buying from the grid.Zero day, the one year anniversary, was the day we found out (with documented evidence) that we produced more than we consumed over the last year. It's a major milestone in our living experiment.

But before I tell you the numbers, I'd like to talk about the weather. I think it's safe to say that the word “brutal” would accurately describe our summer. Numerous major heat records were set this year in central Texas. It was the hottest summer on record, the hottest July on record, the hottest August on record, 27 consecutive days with 100-degree highs, 85 days of 100-degree highs. And we tied our all-time high of 112. To sum: it was very hot.

Ironically, the other half of our summer weather disaster – drought – has actually benefited our numbers, because we haven't had any cloud cover for months, so we've been getting full days of solar generation (with the minor caveat that without rain, our solar panels have been getting a bit dusty, which cuts down on the generation, but only a tiny bit).

So we've had the two opposing forces in our weather pattern all summer – unrelenting heat and abundant sunshine. In all, I would have preferred a more moderate summer. Of course, our winter was unusual as well – we actually had snow.

Before I get to the numbers, a brief word of explanation. There are four numbers involved: the amount we imported from the grid, the amount we exported to the grid, the amount we generated, and the amount we consumed. The grid imported and exported are read directly from the bidirectional meter; the generated amount is from our solar monitoring service, and the amount consumed is calculated from the other three numbers (generated + imported – exported). If this seems overly complicated, relax – the key numbers are the imported and exported.

Enough teasing – here are the numbers:

Imported from grid: 5018 kWh

Exported to grid: 5502 kWh

Generated: 8416 kWh

Consumed: 7932 kWh

So we generated 484 more kilowatt hours than we consumed. Queue the confetti (seriously, don't dump confetti everywhere – it's a terrible waste of resources). If we continue to generate more than we consume, we may never pay an electric bill again. In fact, we could end up with an increasing credit over time. Fortunately, we can contribute some of that credit to a program to assist people who are having trouble paying their electric bill. Plus, I'll have to start figuring out how much extra electricity we'll need if we buy an electric car.

Is this the result I was looking for? You bet! Technically, we could have achieved our zero-energy goals with one less solar panel, but having the extra capacity means we have more wiggle room for our future energy needs.

Happy Zero Day!