I’m happy to be the proud parent of a new TED 5000 home electricity monitor!  A friend of mine happens to be an electrician, so he helped me install the meter inside my circuit breaker panel last night.  I’ll have a full report as soon as I get some time to play with the data.

In the meantime, I wanted to talk about how much you can learn without a TED device.  That’s right, you don’t need a $200 gadget to understand energy use; you just have to change your way of seeing.

Most of us get an electricity or gas bill and look at one thing: the price.  If you’re ambitious, you may even compare it to last month or last year.  But price doesn’t tell the whole story, because tariff increases, warmer days, or changes in the billing period all affect the bottom line.

Many utilities have taken a small step to help – they provide a graph of consumption over time.  Usually, it’s a bar chart, but of course we know that time-series are best represented with a line.

The time series for my house is bumpy, which tells me I use more energy in certain months than in others.  I can see a maximum and minimum amount.  I also appear to have a big peak in the winter and a smaller one in the summer.  Informative, but not particularly helpful or inspiring.

The ideal graph would tell me more than “how much?” – it would begin to tell me “why?”  For instance, why did I use the same amount in November and December? Why is the winter peak higher than the summer peak?  Did my switch to compact fluorescent light bulbs make any difference?

To answer these questions, you need context. Time is one context, but it’s not the real driver of energy consumption for most people.  Weather is.

Take the same consumption data, plot it versus the average monthly temperature, and you get something like this:

Click on the bubble before you hit play to see the trail lines.  You’ll notice that the house displays a very predictable energy consumption pattern, sliding up and down along the curve with the changing seasons (colored by temperature, blue to gray to red).

For convenience, I prefer the static display to the animated one.  I display time on this version through color intensity – historical points “fade into the past” while recent points leap out with greater intensity.  That way, you get a sense for how you’re performing recently vs. last year or 5 years ago.  Red is the most recent month, used to see if my bill makes sense.

Several things to note from this chart:

1.  There are two peaks, which correspond to temperature extremes.

2. The curve “bottoms out” at about 750 kWh.

3. I used almost exactly the same amount of electricity this month (red star) as I did at this temperature last year.

There’s more to discover there (like why November and December of last year had the same consumption…) but more importantly, the graph tells me something about my home’s energy profile.  I can divide the energy use neatly into two sub-categories:

There’s a base level of consumption (750 kWh)  indicated by the bottom of the curve that represents the energy use on lighting, appliances, computers, TV, laundry, etc.  It’s temperature independent.

During temperature extremes, consumption rises and becomes temperature dependent.  That’s my heat pump working to keep me comfortable.

With this picture in mind, I can make some predictions about how energy efficiency projects will affect my monthly bill.

For example, over the summer, I added about 18 inches of fiberglass insulation to my entire attic.  Because insulation prevents heat loss, my heat pump wouldn’t have to work nearly as hard in the winter and I would expect to see the curve flatten out, while maintaining its baseline consumption like this:

Notice, that saves me a significant amount in the coldest months, but I shouldn’t stop there if I want the biggest savings.

Using my TED 5000, replacing incandescent bulbs with CFLs, and line-drying my clothes will help bring down my temperature independent load.  The curve will stay curve-y, but the entire thing should drop down, something like this:

I’m still early in the game, but I expect to see some combination of these changes as we move into winter.

Every building has a unique energy profile, kind of like a fingerprint.  What does your home look like?

Related posts:

1. How to Calculate Energy Savings in a Building
2. Aux Heat Kills
3. The Oracle at TED: HVAC
4. Twilight for the Energy Vampires
5. Where did I go wrong?