Archive for the 'Solar Obsessed' Category

20 Megawatt-hours

20,000 kWh meter pic

Today we generated our 20th megawatt-hour.

It took 837 days to generate 20,000 kilowatt-hours, or roughly 28 months.

Since we moved into the house January 1, 2012, we’ve generated 15.3 MWh and used 10.6 MWh.


Second solar anniversary

Last month marked our second solar year. We produced 8,519 kWh and used 6,410 kWh for a net of -2,110 kWh from June 2012 to June 2013.

At $0.04 / kWh that works out to a credit of $86.41 from the electric company.

That’s a 46% decrease from last year when we generated a surplus of 3,650 kWh and a credit of $159.68.

Not only did we produce less this year, we used more.

Note: with the new plug-in hybrid, we’ll be using even more of our surplus, and saving more. We’re spending roughly 13 to 19 cent’s per mile in gas.  We’re saving an estimated $400 to $600 in gas each year by using electricity (13 miles/day * $0.19 = 2.47/day * 250 days) which the electric company would only pay us about $55 (1,400 kWh * $0.04) if we sold it back as surplus.

Net metering update

Back in our June performance update, we mentioned that June was our first year anniversary for our solar PV system. In New York, the utility keeps track of the amount of power we use and generate (net-metering) over the course of a year and on the anniversary date credits the owner with any surplus power generated. We generated a surplus of 3,650 kWh from June 1, 2011 to June 1, 2012.

After several calls to customer service and waiting 75 days, we finally got our credit from the power company.

Are you sitting down? /joke/


That works out to roughly $0.04 / kWh. That would be what the utility calls the ‘avoided rate’, the price they pay for not having to generate the electricity we sent back to the grid.

Oh well, at least it will pay for almost 10 months of “Delivery Service” fees in the coming year.

Now if New York could just get it’s act together and pass legislation creating a state-wide Solar Energy Renewable Credit (SREC) market. We generated over 8 megawatt hours in our first year of operation. SRECs in nearby Massachusetts are currently going for about $271 per megawatt hour. So 8 megawatt hours in Massachusetts would equal $2,168.

$2,168 sounds a lot better than $159.82 doesn’t it? It would also speed our payback period significantly and get a lot more people interested in solar.

February performance and fun with charts

February was generally warmer and sunnier than January (14% less heating degree days, 38% more sun), not to mention 2 days shorter. This partially resulted in 24% lower energy usage in February. (I say, ‘partially resulted‘ because we don’t have heating energy values separated out from the total load yet.) If you look at it from a daily usage perspective we’re down 18% from January. That almost got us close to netting out to zero for February.

All values in kWh (except HDD) Jan 20121 Feb 20122 Mar 2012
Solar PV generation 369 597
Usage 873 666
Net usage or (generation) 504 69
Average daily usage 28 23
HDD (base temp 68F)3 1,2124 1,0455

1 January values based on meter reads.
2 February values based on TED data.
3 Heating Degree Days (a measure of how many outside degrees in a day it is below a target inside temperature)
4 Downloaded from, Station ID: KALB (Albany International Airport).
5 Calculated from my HOBO outdoor weather monitor hourly data.

I put together a few charts to compare a cloudy day where the temperatures are dropping throughout the day (February 2nd), and a relatively sunny day where the temperature is rising (February 3rd). There’s always a spike in the morning, the heat, hot water, water pump, and coffee maker all generally go on around the same time. But you can see in this first chart that the HDD day values are low in the morning, meaning it was fairly warm outside in the upper 30’s. No need for the heat pump to kick in. There’s little green on this chart meaning we were not generating a lot of solar power on this day. It also means the house inside temperatures were not getting much help from the sun. Notice how the HDD is getting bigger as the day progresses. It’s getting colder out, down in the mid 20’s. There is clearly more energy being used in the evening as a result.

Compare with the next day below. It continues to get colder until about 8am when it reaches 18F outside. Notice that the heat pump has popped on a few times in the early morning before the morning rush. Then the sun takes over and the temps start to rise, meaning the HDD values get smaller. Very little energy used after the sun kicks in. Evening power spikes a few times for cooking and cleaning.

There’s no big surprises here, but it is fun to see the correlation in data.

We also generated our 6th megawatt in February. It took roughly 61 days to generate this megawatt.

Date Days
0 Jun 2 2011
1 Jul 7 2011 35
2 Aug 8 2011 32
3 Sep 13 2011 36
4 Nov 1 2011 49
5 Dec 29 2011 58
6 Feb 28 2012 61

If you have any questions (or spot any errors), let me know in the comments.

Nice curve (cloudless day)

The curve above represents our power generation for February 26, 2012 from 6am to 5pm. It is the first fully cloudless day since I’ve been monitoring our energy usage and solar generation. Note that TED tracks solar generation values negative and usage/load values positive.

It’s nice to see the power generation capability when there are no clouds for an entire day. The two dips in the morning represent two clusters of pine trees low in the morning sky.

Last update of 2011

Lot’s of news this week. We got our Certificate of Occupancy (C.O.) on Wednesday! We can officially occupy our home this weekend.

We worked like crazy last week and over Christmas to finish all the odds and ends for the final inspections. We finished all the electrical Wednesday, 12/21, and had the final electrical inspection the Friday before Christmas. Our water test results arrived Christmas Eve. We spent the rest of Christmas weekend finishing up the porch railings and temporary stairs for the final inspection on Tuesday, 12/27. Our inspector gave us the thumbs up and faxed us the C.O. on Wednesday.

But wait, there’s more… Our contractor Warren entered the Energy Star program with our house. In order to complete the program and qualify under the 2011 rules, we had to get our final inspection and blower door test before the end of the year. This happened Thursday, two days before the end of the year. Final blower door result was 131 cfm, an improvement of 28 cfm from the shell test we did back in September. We’ll post more information on the Energy Star process next month when things settle down. It’s the only certification we’ve chosen to do for the house.

Our kitchen counter tops also arrived yesterday and were installed. The counters are Cambria Quartz (color: White Cliff.) We chose a manufactured quartz counter because we wanted something durable and low maintenance. And we chose Cambria because it’s the only American company manufacturing quartz counter tops. It looks fantastic.

And we generated our 5th megawatt Thursday. It took us almost 60 days to do it. That’s 5 megawatts for half a year. The system went online June 2nd.

We have a few finish work projects to complete. As we were running short on time, Jill found tile contractor, Chad Greenslet, out of Bennington to finish our shower tile job. He installed the Schluter and tile in 2 days, but ran out of tile. We thought we had ordered extra, but somehow miscalculated. The extra tile arrived today, so that project should get finished up next week. Jill is also working with a local glass supplier to install a frameless shower door.

The site-cut maple intended for our stairs is still drying out in our basement. At some point soon we’re going to have to decide if it will be ready in time, or if we should purchase other material for the stair.

95% of the trim is installed. The holes have to be filled and cracks caulked before it gets painted. Doors have to be painted too. Jill is hoping to get the two bedrooms finished this weekend so we can start moving some stuff into them.

Also, a few pieces of siding trim for the basement entry have been sealed and are awaiting installment.

But that is about it. We’re down to the final punch list. We have to be finished in two weeks for the mortgage appraisal. That is our other task – converting our construction loan over to a mortgage. More on that process soon as well.

Solar Update

We generated our 4th megawatt yesterday. Here’s a running tally of the number of days it’s taken to generate each megawatt.

Date Days
0 Jun 2
1 Jul 7 35
2 Aug 8 32
3 Sep 13 36
4 Nov 1 49

You can tell by the number of days that late September and October were very cloudy, not to mention the shortening of the day light hours. As the days get cooler we’ve been using more electricity in the form of leaving the lights on to keep the space warm overnight. Since we’ve installed all the insulation, the interior temperatures have not dipped below 58 degrees.

Here’s for hoping there’s a bit more sun and few less clouds for the month of November.

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