We’re net positive again in 2014!

We used 8,108 kWh and generated 8,348 kWh for a net of 240 kWh for the year. The combination of cold temperatures, less sun and the plug-in Prius brought us close to our net point. Here’s our progress for our first 3 years in the house.

Usage Solar PV Net usage
or (surplus)
daily usage
Total 20,914 25,779 (4,864) 19.1 19,758
2012 5,601 8,856 (3,256) 15.3 5,885
2013 7,206 8,575 (1,368) 19.7 6,810
2014 8,101 8,348 (240) 22.2 7,063

Q4 2014 summary: 7% warmer, 8% less usage and 25% less sun as compared to Q4 2013.

In Q4 last year our total usage was 1,957 kWh. This year is was 1,802 kWh, a 8% decrease. Snow covering the collectors for 8 days and cloudy weather resulted in 24% less energy production in Q4.

Overall, here’s how this quarter and the year compare to 2013.

Charts comparing Q4 usage, solar and HDD

2014 Usage Solar PV Net usage
or (surplus)
daily usage
Total 1,802 1,186 616 19.6 2,213
413 538 (125) 13.3 373
570 400 170 19.0 807
819 248 571 26.7 1,033
2013 Usage Solar PV Net usage
or (surplus)
daily usage
Total 1,957 1,576 380 21.3 2,372
482 674 (192) 15.6 405
559 639 (81) 18.6 838
916 263 653 29.5 1,129
All values in kWh (except HDD which is base 65°F).

Year over year comparison

Chart comparing year over year usage

I like to compare the energy we use each year excluding heat. Our little story chart above, shows our usage and how it has played out over the last 3 years. By far our biggest energy increases have been related to hatching and brooding chickens and turkeys each spring. We managed to raise a year+ worth of chicken and turkeys this year, not to mention all the milk and cheese from the goats. It would of course be cheaper to buy chicken, eggs, milk and cheese, and Thanksgiving turkey at the store, but we like to do things the hard way.

Pie chart - circuit breakdown

We started monitoring an additional 11 circuits in March when we switched to eGuage, but I haven’t had a chance to look at that data in any detail yet. The main changes this year, are increased usage of the ASHP and the ‘everything else’ category which included the Prius plugin for eight and a half months. I’ve also started tracking the vampire loads from things like the induction cooktop & stove, solar inverter and the ASHP. These are things you can’t just unplug. In total these 3 appliances used a minimum of 119 kWh to do nothing. I say minimum because I have only been able to start tracking some of these vampire loads with our new energy monitor starting in March.

Chart showing net zero break even point

This year I started plotting when we net out on energy use versus production. I call it the ‘net zero moment’. This year it happened about 2 months later than last year. Thankfully we didn’t cross over again in December.

Chart showing cumulative kWh used by ASHP Oct-Dec 2012-2014

Last year I noticed that our air-source heat pump (ASHP) used a lot more energy (114% more) in 2013 than in 2012. 2013 was cooler than 2012 but it was also sunnier. I never figured out the increase. This year, the ASHP also used more energy than last year despite being 7% warmer. Both the lack of sun (25% less) and our change in use of the thermostat most likely had the biggest impact. In 2013 I turned the heat off at night. This was generally fine until we had a few days below zero and the heat pump was not able to make up the difference. So this year I tried leaving the unit on and just turning it down to 65F at night. I think this has increased our usage without any real gain in comfort. It seems like it’s really only important to keep the unit on if the next day’s temperatures are known to be below zero, which is where our ASHP has trouble keeping up with demand.

Chart showing kWh used by ASHP in 10 degree buckets

Speaking of ASHP usage, here is our plot showing the amount of energy we used for each 10 degree drop in temperature. If you remember the post from last year, 2013 looks a little different. I realized the ASHP vampire load was throwing off my count of hours. This year I only show hours where the unit was actually doing something, heating or cooling the house. We had substantially more hours below 50 degrees. Most of the ASHP usage has consistently occurred in the 20-30 degree range.

Chart comparing water usage 2012-2014

We seem to be fairly consistent in our hot water usage. Over the year we’re averaging 18.4 gallons/day. That hot water requires 262 watts/gallon to heat. Cold water usage averages at 43.5 gallons/day. In total we used 22,575 gallons on water in 2014. It took 58 kWh to pump that water out of the ground. I’m guessing half of that is water for the various assortment of critters on the farm. They don’t drink a lot, but they do waste a lot.

Chart comparing temperature ranges 2013-2014

And lastly, just because I like this chart, the temperature ranges we experienced this year. In case it is not clear, 2014 was 0.9154149°F warmer on average than 2013.

Happy 2015!

You can see heat maps and detailed charts of temperature and electrical usage at netplusdesign.com. View hourly, daily and monthly values for solar, usage, net usage, temperatures and HDD.

1 Response to “We’re net positive again in 2014!”

  1. 1 Jim Merrithew 3-January-2015 at 5:11 pm

    Hello Larry,
    You tracked the PV energy consumed to plug in the Prius. The PV energy would reduce the consumption of gasoline. Have you considered factoring in the savings of the equivalent energy that the gas would represent?

    You also mentioned that you and Jill are raising critters and that process, directly and indirectly, consumes energy. But, you may drive to the store less for groceries as a result, That self-sufficiency could reduce your total “carbon” foot-print.

    Thanks for the updates and the analysis. Have a wonderful year in 2015.


Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

Latest Uphill Tweets

Enter your email address to follow this blog and receive notifications of new posts by email.

Join 265 other followers

%d bloggers like this: