In Maryland, there are several initiatives that make solar power an easier, more affordable solution for homeowners. First, there are state and federal rebates available when you first install your system that help offset the initial costs. Next, low-interest loans for solar systems make these systems more affordable over the long run. Net metering allows system owners to sell their electricity back to the electricity distributor, offsetting, and even generating moneys on, their electric bill. And last, SRECs help generate ongoing moneys that help pay for the system every month.

We installed as many solar photovolatic panels as would fit on the back (south-facing) of our roof. This equates to 9.75kW of generation potential (under perfect conditions). What we’ve actually generated varies based on the time of day, the season, sky clarity, and a variety of other factors. In the Summer, around mid-day, we’ve seen 9kW being generated before. In the Winter, our generation goes down significantly.

As I’m writing this, Tropical Storm Elsa is on its way here and with the cloud cover we have we’re currently generating 3.1kW of electricity. The house is only using 700W so the remainder is going to the grid where our neighbors can use it.

Since we installed the system, at the beginning of 2018, we have reduced our home’s energy grid-demand by a third (36.6% to be exact). We have also sold more than 10MW of electricity back to the grid which I didn’t calculate into the grid-demand reduction. But this is where it gets complicated. The financial and ledger book entries of electron flows aren’t as cut and dry as just how much energy did you use and not use.

Solar panels are expensive. Installation is expensive. All the electrical panels, wiring, and switches are expensive. When it was all said and done, the cost was figured to be right around 10¢/kWh when the estimated system generation was calculated over thirty years^[3]. We added two Tesla Powerwall battery backup systems to the system which allow us to store our generated power and use it at night or when there is a power outage^[4][5]. Our loan is especially designed for solar projects and has an interest of 2.99%. We financed the entire project over ten years so our monthly payments are a bit higher than what many people would opt for but after that, we will be generating free electricity (kind of). (We actually paid off this loan early so we are saving on not paying the interest on this loan. Haven’t done the figures on this, yet.)

BGE’s rates change twice a year, based mostly on fuel rates and expected demand. As of late, they have hovered around 11¢ to 12¢ per kWh. So, immediately, if our system was built with 10¢ per kWh in mind, we’re already doing better, right?

BGE says that our "efficient neighbors" are using 821 kWh of electricity per month, right now. That’s around $100 per month figuring 12¢ per kWh. But at 10¢ per kWh, our bill would be only $82! That almost a $20 savings in the month of July with running the air conditioner. And this is before we even consider the ~$70 we can get for each megawatt we generate through selling an SREC.

We paid $7,500 for our first Powerwall and $5,000 for the second which adds up to $12,500 for both Powerwall devices, installed. During 2019, we used 2,394 kWh of power that was stored in those batteries. At ~14-cents per kWh, that comes up with a savings up $335^[8]. If we do that consistently during the batteries' twenty-year life span^[9], we will have saved ~$6,700 or about half of the cost of the batteries.

Based on BGE’s upstream supplier, we also saved 1.27 pounds of Nitrogen Oxide, 1.68 pounds of Sulfur Dioxide, and 2,212 pounds of Carbon Dioxide from being generated.

And because the batteries also act as a whole-house power backup^[10], which was used for around 4 hours during 2019, and almost 38 hours in 2020^[11].

Again, in 2019, we produced ~10MWh of electricity. If we had to purchase that directly from BGE, it would have cost us ~$1,400^[12]. Over the course of our twenty-year guaranteed production time frame, that comes to around $28,300 of electricity that we won’t have to buy. But, of course, solar panels don’t just stop working after their guaranteed production time frame. They don’t even stop working after their warranty period. Their efficiency may reduce to below their rated generation output but they’ll keep on generating.