Monitoring My Energy Use

Every time I get a utility bill, I record the amounts used each month (electricity, natural gas, and water).  I've been doing this for more than three years now and have plotted up the trends.  Here's my electrical energy use over the last 3.3 years.  Each year is plotted as a different color.  After my solar power system was installed, I plot the amount produced each month on the top plot.  In the bottom plot I show how much energy was consumed after subtracting the solar production (negative numbers mean putting energy back on the grid).

There are a few things to notice here, that I think are interesting.

1. Our baseline energy use for the household, without air conditioning, is ~6 kWh/day, or an average of 250 watts at all times.  If I want to identify places to be more efficient, I have to be able to chip away at that number.  If I have to do/spend a lot and it only buys me a few watts, it's not really going to help.

2. About 2/3rd of our energy is that baseline load and about 1/3rd is air conditioning.  I could spend many thousands of dollars to change my air conditioner and reduce the electricity use from the AC by ~30%, but it would only reduce my electricity usage by about 10%.

4. It is WAY more efficient to have multiple people living in the same house.  I lived alone in my home in 2012, but my wife lived in it with me in 2013 & 2014.  Focus on the time between March-May since those times aren't susceptible to weather variations (as we don't use heat or AC then).  You can see that the energy use went up by ~15%, when the number of people in the home went up by 100%.  Get roommates people. It's efficient.

5.  March through June, my house is a gift to the environment.  There's a lot of sunlight and we don't need AC, so we put a lot of energy onto the grid in the spring (and a bit less in the fall).

6.  Every month last year except September, I put energy onto the grid.  That's pretty cool.

Solar Panels (2 year update)

The solar panels have now been on my roof for two years.  They've produced over 8000 kWh of electricity thus far, and have prevented nearly 5 tons of CO2 from being emitted into the atmosphere.  Let's see how they're progressing.


This year's totals:
Energy produced:    4027 kWh
Energy consumed:   3157 kWh

Net:  -870 kWh

Last year's totals:

Energy produced:  3915 kWh 

Energy consumed:  3613 kWh 

Net:  -302 kWh 

So this is very good.  First, the panels produced 3% more energy in the second year than in the first.  I suspect this is primarily due to the mild winter with fewer cloudy days.  Still, this is nice because the panels are supposed to produce slightly less each year (less than 1%) due to degradation.  Second, we used 13% less energy throughout the year than we did the year before.  This is a big deal, especially because my wife was home a lot more this year.  The additional savings this year is entirely due to not running the air conditioner as much.  

In summary, in year one we used nine of the ten solar panels and the other panel was producing energy for my neighbors.  This year, we only used the energy from eight of the ten solar panels.  

And I think we can do more.  We're installing ceiling fans and a lot of additional insulation.  Hopefully that will bring down energy use associated with both cooling and heating.

Fun fact, the excess energy produced last year can drive a Nissan Leaf more than 2500 miles!