After a full year of occupancy, I can now share a full year of electrical data on the Passive Bauernhaus:

   PHPP Predicted Consumption: 8,145 kWh

   Actual Consumption: 8,921 kWh

   Average Monthly Electrical Bill: $87.85

   Highest Bill: $123.21 (February 2013)

   Lowest Bill: $63.11 (June 2013)

Armory Lovins, a physicist and the founder of the Rocky Mountain Institute, was the first to really define the cheapest watt. He coined the word negawatt---which is kind of the opposite of a megawatt. Actually, it is the exact same amount of energy as a megawatt, it is just that a negawatt is theoretical. It represents energy that has NOT been consumed, or energy that has been saved.

The negawatt is what energy efficiency and conservation is all about.
 
The idea becomes very important when we start to talk about energy production. To illustrate the idea, I’ll use photovoltaic power as an example. Let’s say that you are interested in PV panels, and you are thinking about installing a PV array at your home or business. The first step is to evaluate the cost of saving energy VERSUS the cost of producing that same amount of energy.
 
Let’s use your entertainment center as an example. You have a TV (Energy
Star® rated), a DVD player, audio amplifier, and maybe even an old VHS player.
Each and every one of these devices is drawing power, even when they are turned OFF (they are designed like that for a variety of reasons). In geek speak, this is known as a phantom load.
 
Using a watt meter, we find that together, these devices are drawing (18) continuous watts. It is energy that is being consumed, but not really put to any good use. How much energy does the entertainment center consume per day? 
                 
     18 watts x 24 hours / day = 432 watt hours / day

This system uses 432 watt hours / day. Over the course of a full year, it will consume almost 158 kilowatt hours. At the going rate of electricity, that will only cost about $16 per year. No big deal, right?

To produce an equivalent amount of power with a PV system, we would need to figure out the solar insolation value for the area. The solar insolation value is how much sunlight hits an unshaded part of the earth on the average day---at maximum power. We call this “peak sun hours.” We can find the value here, on the NREL (National Renewable Energy Laboratory) website. For our area, it is approximately 5 peak sun hours / day. Here’s the math for figuring this out: 
                 
     432 watt hours per day / 5 hours per day of sunshine = 86.4 watts
 
Of course, no system is 100% efficient. Most PV systems are “derated” by 15% -20%. Let’s avoid getting too detailed here. We’ll just call it a 100 watts.
 
PV systems are currently being installed for $3 - $5 / watt. That means we’ll need to spend $300 - $500 in order to generate the same amount of electricity that is being consumed by the entertainment center.

That energy is not so cheap anymore . . .
 
What is the cost of saving that same amount of energy? Well, if the entertainment center is plugged into a switched outlet, it wouldn’t cost anything; you would simply have to turn OFF the system at the wall switch, just like you turn OFF a light.

If it’s not on a switched outlet, you could install a power strip and turn it OFF there. Power strips are pretty cheap, usually < $10 each. Most people would find that too cumbersome; they would probably want to install a “smart” power strip like this one. It automatically turns OFF these devices when you power down the TV, eliminating most of that phantom load. These sell for ~ $30.
 
So . . . you can see that the negawatt is the cheapest solution. In this example, it ranges in cost from $0 - $30, compared to $16 for the annual cost of electricity, or the $300 - $500 cost of producing the same amount of energy using a renewable energy (PV) system.

How many negawatts have you produced lately?!

In the last post, I talked about cost parity and Passive House.

In this post, I'll take it out of the theoretical world, provide a clear example.

We moved into our Passive Bauernhaus in June 2012, but didn't get our first full month electric bill until July. Since then, the electric bill for our Passive Bauernhaus has averaged 663 kWh/month or $81.04/month. This total includes the typical $25 - $30 service charge.

Since it is an all-electric house, we only pay one bill. There's no propane, natural gas, or firewood. Electricity covers all of our loads:

    Well water (pumping)
    Domestic Hot Water
    Heating / Cooling
    Ventilation
    Lighting
    Appliance Loads
    Plug Loads (computers, TV, alarm clock, coffee maker, etc.)

In the previous year, we lived in a Fishersville area townhouse. The townhouse was built to existing codes, circa 2006. In terms of usable space, it was very similiar to the Passive Bauernhaus---4 bedrooms and 3 1/2 baths. It was a multi-family development, so we were sandwiched between two other units of the same size. It used propane for heating, domestic hot water, and the clothes dryer. And, electricity, of course.

I recently dug into our townhouse financial records to look at our utility bill history. After tallying the numbers, our average monthly townhouse bill came to $243.83 (for a full calendar year). The lowest month came to $122.91; the highest jumped to $429.87.

We haven't lived through a full calendar year in the Passive Bauernhaus, so it may be a little premature to call this one . . . but I can't resist. I say that because we're tracking right in-line with the PHPP energy modeling software.

Here's the bottom line: we're saving > $150 / month.

It's not earth shaking, but it's not too shabby either. It becomes significant when you project this over a typical 30 year mortgage.

And . . . it provides the margin that allows a Passive House to reach cost parity.