Archives February 2021

Going Solar, Part Six: Results!

West-facing panels, note anti-pigeon fencing

We have ignition!

NV Energy replaced my meter and gave me thumbs up on January 6, so I pulled the handle to connect my panels to the grid (and my home). That afternoon, the panels generated 4.441 kWh of AC energy. The first full day was 18.292 and we were just getting warmed up as the days after that registered 24 kWh or more per day. Overall trend was increasing production as days grew longer.

January 2021

I started getting data from NV Energy on 1/16/21 so for the last 16 days of the month I know I received 370 kWh from the grid and delivered 200kWh of solar power to the grid. My total consumption of electricity for those 16 days was 529 kWh, so by my calculation the panels saved about $20. Add in the 10 days without data and I may have cut my expected $65 bill to $35. I’ll let you know exact numbers after I receive my first bill.

These numbers are in line with the estimate from my solar contractor that my panels would generate approximately 628kWh every January. From 1/6-1/31 (25.5 days) they actually generated 593, average 23 per day. 23 x 31 = 713 for a conservative estimate of what total January production might have been. PVWatts was a little optimistic predicting I might generate 902 kWh, but they apparently assume mostly-sunny days, whereas about 1/3 of the days this January were cloudy or partly cloudy. Daily production ranged from 8 kWh to 36 kWh depending on amount of sunshine.

Is it worth it?

Considering that I made the first of 144 loan payments of $182.71,saving $30 on my first monthly bill might not be cause for much celebration. Fortunately, the savings should be much greater in warmer months, and the up-front $5800 tax credit reduces the cash flow pain significantly.

A lot depends on how much I get for delivering excess solar power to the grid during summer peaks. In July I should be able to generate 1500 kWh and deliver much of that back to NV Energy for about 22 cents per. That’s a big chunk of change if I use the AC sparingly during peaks and don’t crank it up too much in the off-peak hours.

The future

Assuming my installation proves reliable and free from major maintenance costs, most other factors seem likely to increase cost-effectiveness of my investment:

  • Summer days grow hotter
  • Electricity rates increase
  • Public perception of the value of solar panels increases

Meanwhile, I can take some satisfaction that I am reducing my carbon footprint (particularly important in US with its inefficient carbon-based generating plants) and have somewhat limited the risk of climate-related impact on energy costs for my home. After one month of production, my monitoring program cheerfully informs me I’ve saved the planet from 1,222 pounds of carbon, the equivalent of planting 9 trees.

At this early stage, it appears I may go a very long time without paying anything for electricity. I will have to pay a small monthly fee to remain tied to the grid.

First Bill (January)

Today I received my first post-solar bill from NV Energy. It covers the day of installation (1/6/21) to 1/28/21, 22 winter days. The combination of TOU Rates and Solar Power are saving a lot of money.

The grid delivered 423 kWh and the panels sent 323 kWh out of about 500 kWh generated from solar panels to the grid, for a net 100kWh billed at full rate, total $6.25. Various fees on the full 423 kWh were $1.36. Electricity costs total $7.61 or $0.35 a day. The base service was $9.53 for the partial month, making the total bill $17.24, an average of $0.78 per day.

Last year my daily average was $2.24, $1.46 more per day. This year we are using a lot more electricity due to the pandemic. Last year we used about 15 kWh per day but this January we used almost double, 27kWh per day.

27 kWh at full rate would have been about $1.69 per day (base service additional.) TOU saves about $1 of that. My original projected solar savings, pre-TOU were $0.12 per day, so it looks like my projections were very conservative.

These numbers will be very different in summer (June-September), when costs and savings (in sunny hot Nevada) will be higher, and conservation during peak hours will be more essential.

February, 2021

For the period 2/1/2021-2/28/2021, my solar panels generated 971kWh. That exceeds the estimates from PVWATTS (924) and my contractor (790). I used 449kWh from the grid and sent back 703kWh for a net of 254kWh to my credit (for use in summer.) My total consumption was 717kWh (971-703+449) which would have cost $47.11 from the grid. Instead my bill was an effective credit of $9.89 for a savings of $57.00.

March, 2021

Solar panels generated 1274 kWh. This exceeds the estimate from my contractor (1100) but didn’t quite reach PVWATTS (1278). I used 486 kWh from the grid and sent back 993 kWh for a net of 507 kWh to my credit. The credit does not go toward the base (about $15) but it pays for electricity including basic delivery fees for the grid (about $1.50 for the 486 kWh). My accrued credit so far is about $30 which will probably be used up in summertime.

In March my total consumption was 767 kWh (1274-993+486) which would have cost $50.37 pre-solar, but combined with my credit of ($21.06) makes a total savings of about $71.43 for March. This is based on TOU rates which are about half normal rates from NV Energy during non-peak hours.

April, 2021

Solar panels generated 1475 kWh. This exceeds the estimates from my contractor (1386) and PVWATTS (1404). It was was a sunny, cool month with only 2 or 3 overcast days in Las Vegas. The average of almost 50kWh per day is probably getting close to maximum production from my 7.92kwP system for any month. Production usually peaks from 6-7 kWh around noon, with occasional spikes above 7. Those spikes may be due to a passing cloud cooling the panels followed by a burst of intense sunlight on the cooled panels.

I lost 1/2 day production due to inverter malfunction. A simple reset fixed it, and it was a good reminder to keep an eye on it every morning.

I used 549kWh from the grid and sent back 1139kWh for a net of 590kWh to my credit. My accrued credit so far is about $55 which will be used up in summertime.

In March my total consumption was 889kWh (1475-1139+549) which would have cost $58.45 pre-solar (TOU rates), but combined with my credit of ($24.35) makes a total savings of about $82.80 for March.

Last year’s bill was at standard rates, before I discovered TOU. At standard rate (0.1134 incl tax) my electricity cost would have been $100.81! So I saved $42.36 by using TOU rates, and $82.80 from solar. Last April’s bill was $128.20 for 1136kWh, this year’s was $13.18 (for the base).