Living Sustainably
in the shadow of climate change

March 2015
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Reviewing our energy use and costs
Filed under: General, Solar Power, Solar Heating
Posted by: Guy @ 12:44 pm

Over the last 13 years since we purchased our home in Maine I have been working at reducing our energy footprint as part of my commitment to live as sustainably as practical. My strategy has been to reduce usage by improving things like building insulation and consumption in general. But also I have added renewable energy sources such as a solar heating system for the hot water in our home, and the solar electric system I installed. I decided to review my progress so far since I have extensive data on all of our energy sources and costs.  This information is derived mostly from our utility bills.

We use propane to heat the house and also for cooking, clothes drying, and water heating.  Below is a chart showing our annualized cost for propane per heating season.  Some of the variations such as the spike in 2010/11 are due to fluctuations in the cost of propane, but the trend is largely due to my efforts since the cost per gallon has been increasing.

Not factored into our relatively low propane costs is the fact that we burn approximately 2 cords of firewood per year at a cost
ranging from $300-$500 per year. Last year we spent $425 for firewood which brings our recent total heating cost to a little over $1400 which is less than half the state average for home heating costs.

As you can see our propane consumption dropped about 50% over the years from almost 800 to a little over 400 gallons last season. Part of the reason for our initial lower cost was that our home (constructed in 2001) was reasonably well-built, insulated and relatively tight compared to an average home. Some of the things responsible for this reduction are:
* Improved basement insulation added to exterior concrete walls.
* Tightening up the building envelope by foam insulating air gaps around window and door framing.
* Adding interior storm window panels and closing honeycomb insulating shades in the cold winter nights.
* Weatherstripping around exterior doors and improving attic insulation.

Thanks to the solar power system I installed, our average electric bill would be around $10 if we did not have the Chevy Volt electric vehicle which adds approximately $45 per month to our monthly bill.

The $45 average electric cost to charge the Chevy Volt is significantly offsetting our gasoline usage (and cost) for that vehicle since we drive in electric mode about 80% of the time.  (The remaining 20% of our miles driven in “range extender” mode is at approximately 40 mpg.)  And since a large percentage of the charging power for the Volt comes from our solar array in the summer, we are driving for free and largely carbon neutral during those months.

One can look at all of the investments I have made in reducing our energy footprint in terms of return on investment. In actual dollars most of these investments have already paid for themselves, such as the solar hot water heating system which according to my calculations paid for itself in approximately 4.5 years:

In general investing in energy reduction yields a better return than investing in the stock market. Even my relatively expensive solar power installation that has cost me over $25,000 would pay for itself within 16 or 18 years assuming it had been financed at below 5% interest.  Since I have already paid off that system, the energy savings is all pure profit at this point.

6 Responses to “Reviewing our energy use and costs”

  1. RJ Says:
    Very impressive. I wonder how the economics of your grid tied system would change if you bought similar equipment today? Would the payback period go down? Obviously some incentives are different, but the federal 30% remains and it seems pricing has gone down. I have seen self service car washes with solar in San Antonio, so it is certainly becoming more mainstream.
  2. Guy Says:
    RJ, Yes, prices have plummeted by nearly 50% for the solar panels since I installed the bulk of my system. FMI see this post: So my system would now come in around $16K with a much shorter ROI. Solar is reaching grid parity in many states with high utility rates and good incentives + low finance rates.
  3. Jodie Says:
    Guy, do you also have a chart on the amount of propane you used? Have you been consistent in the amount of propane irrespective of the price? and has the price fluctuation influenced your amount of use?
  4. Guy Says:
    Jodie, you can see more detailed info on our propane use on this page - scroll down to the bottom to see the chart.
  5. Debby Says:
    Of course. Our house is on etlrecic, powered by a 5kw solar system. The AC, dryer, refrigerator, water heater is all etlrecic. Our heat is from a wood stove, but we could put in a whole house etlrecic heating unit if we wanted. No problem. I don’t know much about wind energy, but I know a house can be powered solely by solar power. Putting in wind power would be another expense.You would have to pay up front, when the house is bring built, but the monthly costs would be next to nothing (depending on whether you’re hooked up to your etlrecic company’s grid versus on rechargeable batteries out etlrecic company changes us about $6/month for the privilege to be hooked up to their system).
  6. Guy Says:
    Debby, I am pleased to meet another person another person with a solar powered home. If you ever want to move away from wood stove heat you should look at air source heat pumps. These units are up to 400% efficient and are the best way to utilize electricity for heating and cooling. Regarding wind energy, it is not as cost-effective as solar, and there are annual maintenance costs that can be really significant depending on the equipment you use.