Updated Electricity Plot

So, here’s an updated plot of our electricity usage since Sept, 2002. You can see that we’ve been working hard!

But here’s the interesting thing. That last dot is 2008, the first year that we had central air all summer. We still dropped in electricity usage, but not as quickly. So, in the second derivative, it’s flattening out.




Here’s another view, which helps explain what’s going on. I’m plotting average KWh/day for each month of the year. The blue bars are the six year average, and the red bars are this year. You can easily see that while July and August of this year are substantially above the prior average, and September of 2007 is a little bit above the average, the other months are down. In some cases, way down.

The winter peak is interesting. That’s the electric clothes dryer.

But check out May. It’s the lowest usage month, and so in a sense gives our baseline usage, for critical things like the refrigerator and lights.

In May, we averaged about 4 KWh/day. That’s a rate of 0.17 KW, or 170 Watts. That means we’d have to generate at a rate of around 950 Watts to power our house entirely by solar panels in May. That means I’d need, say, five 200-Watt panels. According to my online research, that would come to less than $5000 for the panels. A little further looking around reveals a cost of about $8633 for a complete grid-tied 1050 Watt system (approx 5.9 KWh/day, or 176 KWh/month). That’s totally affordable, especially with rebates and tax breaks, which can sum to several thousand dollars.

Now, that’s for our best month. And I’ll need to look up all the tax breaks and rebates. And, we need another year or two of pushing the numbers down, to see how low we can go. But our baseline usage is now within shooting range of an affordable solar system! I’m really proud of that.