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Numbers To Chew On

Paul Kando

I am often asked how much we spend on heating our house. Well, strictly speaking, we no longer have a heating bill. Electric “mini split” heat pumps heat our house now, so our heating costs are part of our electric bill. To answer the question I have to run some numbers based on monthly records I keep on our home’s energy use. Here are some, covering the year beginning December 2015 and ending November 2016.

Our House
photo credit: Paul Kando

Throughout that period, we paid CMP $654.16 for power supplied and $750.12 for power delivery (transmission), for a total of $1,409.28. This was our annual electric bill, including heat for the house. To tell how much of this was for heating, I had to determine our base load, i.e. all the year-round uses of electricity except winter heating.

The customary way to do this is to average the lowest-cost three months of power consumption and multiply that value by 12. In our case the result is $514; the dollar value of electricity purchased from CMP during the above 12 month period for every purpose other than home heating. Deducting this from our total bill of $1,409.28 leaves $895.28, our annual heating cost.

We no longer burn oil. The last year we did, we burned 880 gallons. Multiplying that by the current average Maine #2 oil price of $2.26 gives a total of $1,988.80. Deducting our heating cost of $895.28 leaves a balance of $1,093.02, the amount of money we have saved for the year, using heat pumps rather than burning oil.

The above numbers include the power generated by the solar panels on our roof, the value of which came to $907.64 for the year. So, if we had no solar panels, we would have to add this amount to our CMP bill, ($1,409.28 + $907.54), bringing it to $2,316.82. Deducting our $895.28 base load from this would leave $1,421.54 for our heating cost. That would still be a $567.26 saving for the year compared to oil heating at the current oil price. Of course, all summer long, we also enjoyed air conditioning courtesy our heat pumps, a free bonus.

Where does net metering enter this picture? Over the year our solar panels generated 6051 kwh of electricity, worth $907.64. Of this we had no contemporaneous use for 2,814 kwh, excess power our solar system automatically metered into the power grid. The value of this was credited to us against our electric bill, via net metering.

It maybe worth noting that this power was fed into the grid during peak demand periods, when CMP would have had to purchase that power at peak rates. Those rates are roughly 5 times the off-peak rate — a significant cost penalty. Therefore our PV panels are saving money for everyone on the grid, not to mention reducing transmission losses as well.

Remember this next time some ignoramus tries to feed you the alternative fact (hogwash in plain-talk) that rooftop solar systems are subsidized by other rate payers!