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|
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!