Electricity generation for 2018

Today I received my December electricity bill from Baltimore Gas and Electric (BG&E) which reminded me that I hadn’t actually looked at our electricity usage over the past year since we had the solar panels installed. We started producing electrical power on 19 February 2018 and by April we were making enough to completely offset our usage. According to BG&E, we had actually banked enough carryover electricity to not have a bill until November!

Table 1. Solar generation per month for the year of 2018
Month	kWh
February	148.7
March	974.3
April	1,190.7
May	1,047.5
June	638.4^
July	1,073.2
August	1,055.3
September	612.1
October	373.9
November	291.4
December	275.7
2018	8737.2^

^The receiver that collects the data was out of service for part of June so it failed to collect more than a MW which is not reflected for that period of time. It does account for it in the overall annual total, however.

Seasonal variances

There was a noticeable drop in generation in September and October. After summer solstice the planet starts to shift its angle in relation to the Sun. This means the sun is now dipping down behind trees that still had leaves on them. I was hoping that once the leaves came off the trees I’d see a rebound in power generation but that hasn’t happened yet. I’m postulating this is because of cloud cover and other weather-related events. Of course this is the same time I’m running my heat which is very inefficient.

Batteries

We also have two Power Wall battery packs that, during the Spring and Summer, allowed us to basically live off the grid with our 9.75kW solar installation on the roof. In the Winter I just don’t have enough charging capacity to recharge them quickly so I’ve switched them to backup-only mode. They should work well for us if we have a power outage (and they have) as we can better control our usage in an emergency situation and try to limit the amount of area we are going to heat which will reduce the amount of our electricity demand.

What’s next

I wish we had enough consistent wind to be able to use a turbine here. Oh well.

I need to figure out a better way to clear snow off the panels as we recently found out that six inches of snow completely blocks the penetration of the Sun’s rays resulting in no power generation. This is not a big deal unless we are also suffering from a power outage and I need to recharge my Power Walls.