In the previous two posts, we studied the electrical production from our 26 module, 8.58 kW array from 2020 to 2023 and compared it against our electrical consumption for the 2020 solar year.
The actual monetary savings of our photovoltaic array over the first three years averaged $1,257 per year, which is slightly more than we expected. At this rate, we are on track to make our $10,047 investment on the array back by year eight.
Looking to the future, if this savings rate continues, the array will have also paid for most of the $31,971.04 roof project investment (the cornice repair, parapet repairs, and reroofing) by year 25.
Slicing and dicing the savings
Our solar installer, Lisa Albrecht from All Bright Solar, shared an Excel spreadsheet with me that allowed me to take a detailed look at our savings. I input the various charges from our electrical bill plus the electricity we pulled from the grid, the electricity we fed back into the grid, and our monthly rollover credits, and it shows me what I would have paid without our solar array versus what we actually paid.
Our savings per solar year (April 1st through to March 31) were as follows:
| 2020 solar year | $1,175.76 |
| 2021 solar year | $1,232.94 |
| 2022 solar year | $1,361.86 |
| Three year total | $3,770.56 |
Our savings follow closely the Return on Investment (ROI) calculations that Lisa shared with us when planning the installation of our solar array.
Our out of pocket investment into the solar array was $10,047 after the various rebates. Subtracting the first year’s savings reduced our liability from $10,047 to $8,888 (prediction), or $8,871 (actual). In other words, our ROI for the first year exceeded the prediction by $17.
Subtracting the second year’s savings from the net gain/loss of the first year reduced our liability to $7,697 (prediction), or $7,638 (actual), with the ROI exceeding the prediction by $59 – and so on…
As I mentioned in a previous post, the state incentive we received is based on how much kilowatt hours our 8.58 kW photovoltaic array is predicted to produce over the first 15 years.
10% of that incentive is withheld until year 15 and released as long as we meet the predicted production target. Because our production is exceeding the prediction, it would be safe to assume that we can add another $1,160 incentive payout to year 15 in our ROI calculation.
So far we are on track to make our money back on our $10,047 investment by year eight, giving us an ROI of 12.5%. After that, we can pocket all the savings from our 8.58 kW photovoltaic array. If Lisa’s predictions hold true, we would also have saved around $31,838 on our electrical bills for our 4,500 sf building with its three apartments by year 25.
That $31,838 would cover 99.5% of the cost for our roof project (the reroofing, cornice repair, and parapet repairs).
That all said, I don’t expect to exactly meet these ROI targets, because the numbers don’t account for maintenance and repair costs we may face over the next 25 years. But we hope to get close to them.
At this point I feel I need to clarify again that the savings are not just because we bought into a renewable energy system and slapped a photovoltaic array onto our roof. These savings were made possible because our deep energy retrofit significantly reduced the overall energy load of our building first, which then was followed by a renewable energy investment.