ART TEC - Solar Power - Real Time performance stats

PERFORMANCE HISTORY

I have 39 solar panels installed ranging from 175 W to 375 W per panel. In 2021 I installed heat pumps in both buildings and only use propane as backup, the trade-off of having these energy intensive devices is I have a significant electric bill in January February and March that runs to many hundreds of dollars due to the low solar production here in Maine. However, from May through October I only pay the utility for connection fee of about $24. In the late summer and fall I accumulate kilowatt hour credits that are applied to my bill in the winter.

The statistics shown come from my Enphase energy monitoring system data that I put into a spreadsheet to create the charts below and also from my electric bill.

C lick here to see live and historic energy production

PERFORMANCE STATISTICS

The chart below shows the estimated power that my solar panels should generate based on calculations from the PVwatts calculator provided by the National Renewable Energy Labs. The calculations factor in weather data from the nearest reporting weather station to account for seasonal overcast. The actual energy produced is obtained from my monthly reports provided by the Enphase Enlighten web interface (the real-time performance data from my micro-inverters). I update the graphs in the middle of each month after I get my utility bill.

In the chart below actual usage lags behind the estimated due to the discrepancy between monthly estimated data and the billing cycle that ends mid-month. The increases in production are due to adding solar panels.

Enphase have released a study showing that their microinverters out perform PVWatts calculations by up to 8%. They looked at regular string inverters and found that they underperformed PVWatts numbers by up to 8%. So this validates my decision to invest in Enphase inverters.

My electrical power usage varies due to variations in my use of energy intensive power tools, miles driven in my EV. Energy consumption also peaks in the winter when I use the heat pumps - it stays below freezing for months here in Maine. When I purchased my first Chevy Volt in May 2012 my monthly usage went up by around 3-400kWh/month - and a bit more in 2024 when I got a 2021 Chevy Bolt.

date array panels
installed Watts/
panel Total
panels Total
Watts

September 2009 W 21 175 21 3675

August 2010 W +2 175 23 4025

June 2011 W +2 175 25 4375

July 2011 W +1 180 26 4555

May 2012 - Purchased Chevy 2012 Volt
(uses around 3-400kWh/month for charging)

June 2012 W +3 230 39 5245

March 2013 S +2 245 31 5735

October 2016 S +1 245 32 5980

November 2017 - Purchased 2017 Chevy Volt

April 2021 - Installed Heat pump in house

November 2021 - Installed Heat pump in workshop

November 2021 S +5 375 37 7855

March 2022 S +1 375 38 8230

January 2024 - Purchased 2021 Chevy Bolt

The chart above shows power imported from utility in red, solar energy generated in yellow and net power in green. Basically, the chart shows how much energy I saved by using solar power, which is clearly more in the summer months. At my latitude in Maine USA (44 degrees) we get about 1/3 of the solar energy in the winter compared to the summer. My 2021 Chevy Bolt uses over 400kWh/month year round. I added 2 heat pumps in 2021 which dramatically increased my consumption in the winter.

Note that my utility has increased their minimum "connection fee" from about $25 to just over $40 as of June 2025.
This is an unfair punishment for those of us who choose to go solar in my opinion.

My utility info:

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