Solar Production – Summer 2013 and Time-Of-Use Experiment


It hasn’t been the best summer for those of us in New England with solar panels. The weather has been more reminiscent of Seattle’s gloom than Boston’s sun. But I’m hoping for a beautifully sunny fall and maybe a little Indian summer to go with it. Additionally, I have decided to commence a 1-year experiment with NStar’s Time-Of-Use rate.¬†This residential rate bills you different amounts for usage during different times of the day, peak and off-peak. And since all my solar generation occurs during the peak usage time, I figured it may be a way to even further reduce my electric bill.

There is a significant difference between the two rates, as peak usage costs 28 cents per kWh and off-peak usage costs 12 cents per kWh. Compare that with the standard residential R1 rate of 16 cents per kWh. There is also a $9.99 flat monthly fee which is slightly higher that the R1 $6.43 fee.

The hours that define peak usage vary between the summer and winter months. From June through September, peak is from 9 am to 6 pm weekdays whereas from October through May, peak is from 8 am through 9 pm weekdays. Off-peak is everything outside those hours, including weekends and holidays.

I’m hoping to have some large credits during the peak summer months as the energy I generate will be during the peak period when the rate is much higher. The biggest question mark in my mind, is how much extra it’s going to cost me during the 8-month long winter season where the peak period includes most of the evening.

Here’s the numbers:

Period Ending Production As % of Usage Savings
Sep 21, 2012 616 kWh 77.6% $92.34
Oct 23, 2012 449 kWh 69.7% $67.32
Nov 23, 2012 313 kWh 50.2% $46.93
Dec 21, 2012 188 kWh 33.2% $28.19
Jan 23, 2013 195 kWh 35.0% $30.05
Feb 22, 2013 259 kWh 47.9% $40.02
Mar 22, 2013 325 kWh 60.4% $50.52
Apr 24, 2013 715 kWh 118.6% $111.14
May 23, 2013 717 kWh 142.1% $111.45
Jun 21, 2013 640 kWh 90.2% $99.89
Jul 24, 2013 704 kWh 60.4% $113.36
Aug 22, 2013 617 kWh 56.5% $91.08
Overall 5,738 kWh 68.8% $882.29

If there seems to be some inconsistency, it is due to weather, monthly usage fluctuations, differences in the number of days per billing period and NStar price changes.

This month showed a decrease in my electric bill of $1.91 on TOU versus what I would’ve paid on R1. However, even with my solar panels, I still used 66 kWh of NStar’s electricity during the peak period this month, and I was hoping to have a surplus. So I’m not convinced this is going to be a profitable experiment, but I probably won’t find out until next summer.

[8/18/14 edit: For an update of my Time-Of-Use experiment (including a revision to this month’s bill), please see the newer blog post entitled¬†How to Increase Your NStar Credits by Almost 20%.]

We shall see!


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2 thoughts on “Solar Production – Summer 2013 and Time-Of-Use Experiment

  1. Pingback: How to Increase Your Solar Payback by Almost 20% | Massachusetts Solar Information Blog

  2. Pingback: How to Increase Your NStar Credits by Almost 20% | The Energy Miser

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