(This is the latest in an on-going series. Here is Part 1).
In my 9 month update I predicted the following:
As the days get longer and the sun gets higher, here are my predictions for the next 3 months:
- January we will still be in the red, using more than we produce, but less than December. I am hoping we cut the December overage (475 KWh) in half.
- February we will do even better, and I hope we cut the overage in half again.
- That would mean we get billed for about 240 KWh in January and 120 KWh in February, or 360 KWh total.
- In March I expect we will generate a surplus.
So, how did the year turn out, and how good were my predictions?
Not as good as I had hoped. I got January very wrong (240 predicted, 416 actual), was closer for February (120 predicted, 169 actual), but we did have a surplus in March. It was a very cloudy winter and as the song says, ‘clouds got in the way.’
The full year looks like this:
Total cost for the year was $233. About $100 of this was for the meter, which we would have had anyway, so the net cost was about $133. After factoring the $39 that BGE paid us in May (this is an annual payment that zeroes out the surplus each year), our cost was $94.
I logged our accumulated production on 3/26 at 9.67 MWh. Adding this to our meter reading, it appears we used 10,120 KWh and produced about 9670 KWh this past year.
Using 0.13 per KWh for an average cost of electricity delivered to our home this year, without solar panels our annual electric cost would have been 10120 * .13 = $1315.
This means our savings this year was $1315 – $94 = $1221.
Understand that each year’s savings may differ due to the amount of solar output, our consumption, the cost of electricity delivered, and the value of SRECS.
We will receive $455 for our SRECs (the check for the Jan-March quarter comes later).
This makes our first year’s net gain work out to $1221 + $455 = $1676. That is just over 10% of our net cost (after tax credits from the federal, state, and local governments).
All things being equal we are looking at a payback of around 9-10 years.
Since trends never continue perfectly any change in the above factors will change this date. But the panels are supposed to produce well for at least 25 years.
It appears the net cost of electricity delivered is trending down towards 0.12 per KWh, so the payback might turn out to be a bit longer.
Still, it is nice to have no electric bill 8 months of the year, a small bill for 2 months and a reduced bill the remaining 2 months.
The picture above shows the lifetime production of each of my 34 panels. I remembered to take it a day or two after I hit the one year mark. There was also a software error in the application that captures this information, so in both ways this picture shows approximately what each panel produced.
The best panel produced over 318 KWh. The lowest producer was about 264 KWh. In general the best producing panels were at the top and on the right (east) side of the array.
It appears to me that if we had installed two more panels that were in this range, we would have broken even for the year (meaning we would have produced as much as we had consumed).
Please let me know if you have any questions about solar panels or any related topic you want me to cover.