For many reasons, decided that installing my home solar panels was the best approach the least of which is the significant labor and markup cost savings over contracting with professional home solar installers. After some investigation and research, I took a big gulp, then moved forward.
Sizing my own residential solar system was relatively easy for two reasons. The first is that our utility bills give the usage for each month for the past year. This eliminates the need to make up a whole system load chart. We could decide the size of the solar array we needed simply from these utility bill numbers. The annual total showed that we are using an average of 5.87 KWH per day, which I rounded up to 6 kWh per day.
The number of kilowatt-hours (kWh) we use continues to amaze me, even though I’ve known it for a while now. The average american home uses about 20 kWh per day. We live in a 1,200 square foot (110 m2) house, and have most of the modern appliances, except for a microwave and a dishwasher. We do all the things most households do, except that the television is only on for an average of hour a day or less.
It is said that for every $1 of efficiency measures, you save $3 to $5 in RE generation costs. This also means major savings if you are using grid electricity. It is difficult for me sometimes when I see how easy and cheap it is to save large amounts of energy, and yet most people simply aren’t awareof their energy use.
Solar array sizing was easy for us because of the limited roof space. I have only a small area of available south-facing roof. It is triangular, with a 25 foot (7.6 m) base and 12.5 foot (3.8 m)height, totaling 156 square feet (14.5 m2). Obviously, only a portion of that is usable, the part that can fit a number of rectangular solar panels without going over the edges. I drew up a small diagram of the solar system, and played with various sizes of rectangles, based on the sizes of the solar panels listed in the specs by the various manufacturers.
In the end, I decided on a little less wattage to be able to go with fewer large solar PV panels instead of more small panels. I liked the idea of fewer connections and fewer panels to install, fewer holes in the roof, and a quicker installation. I opted for six 165 panels, since the size and output was right. I could easily fit the six panels on the roof, and they added up nicely to 990 W and 144 V nominal when connected in series, enough for one string on a high voltage Sunny Boy 1800 watt inverter.
Putting it all together, I ended up with a very straight forward solar system design about 1 KW of solar panels and a Sunny Boy inverter. The SunnyBoy was a given. It’s a high voltage inverter, which makes for much simpler wiring, and the price is right.
One of the toughest part of the residential solar installation was working on the roof. It took almost a whole day to cut the cedar shakes away down to the slats so we could bolt the solar mount standoffs to the rafters, and then get the roof jacks over the standoffs and under the remaining roof shingles to make a watertight seal. Not a job I look forward to doing again I would probably hire this out next time.
Once that was done, it was all very easy. I am lucky to have a friend who is an electric vehicle whiz, who is expanding into solar, around to give me a hand. Early in the day, we got started. The six solar panels went up quickly,with the positive, negative, and equipment ground from the series string going into a weather proof solar junction box, and then into 1/2 inch EMT. The EMT goes over the roof line and gutter, under the soffit, and around to the DC disconnect, which is on the back side of the house. I wanted the solar inverter and disconnect on the back side of the house out of view, and in a place where I would have easy access to it, right out the back door. It is also important to note that inverters like the SMA Sunnyboy work better in the shade.
We used #10 (5 mm2) THHN electrical wire for the 25 foot (7.6 m)run from the panels to the inverter, which gave us less than 2 percent wire loss for 25 feet (7.6 m) at about 5 A. From the solar inverter, the AC also ran via #10 for the 70 foot (21 m) run to the AC disconnect. This was more than adequate for this distance, but again ensured minimal line loss.
The service panel for this house is on the detached garage about 25 feet (7.6 m) from the house, so we ran the wires in 1/2 inch EMT under the house, and made use of the underground 1 inch EMT that exists to bring the utility feed from the service panel into the house. This is where a good wiring fish tape was invaluable!
From there, it was a (relatively) simple hook-up from the AC disconnect to the service panel. This older panel uses stab-lock circuit breakers, and there wasn’t an available slot. So I had to buy not only a single-pole, 20 A breaker for the solar to connect up, but also a dual-pole, 20 A, 220 V breaker replace a 20 A, 220 V, four-pole breaker to free up a slot. That cost me US$97 for used circuit breakers! If it was myown house, there’s no question that I would have just upgraded the whole panel. Painful process just rewards and that was it. On a warm, sunny Sunday, we threw the switch and watched the SunnyBoy go through its initial checks. After 5 minutes, we saw it start producing clean solar electricity that we owned. We had a small party with champagne for all as we celebrated our (almost) solar energy independence.
As strange as it may seem, the most difficult part of the installing my own custom solar system was waiting for the rebate. I lost about five weeks on the installation time waiting for them to approve my application, which they lost, couldn’t figure out, couldn’t properly tell me what I was missing, and just basically abused. It was a trying experience, but in the end I got my rebate, and all was well. A lesson learned: triple-checking that you have everything in order can save weeks of time when people who don’t care to help are involved.
And now for the rewards! The house here isn’t an ideal place for a solar system, since I estimate that we are getting about 30 percent shading. We would see almost complete shading for the winter months of November through February, with the hours of available sunlight per day creeping up until finally at the end of April,we would get a full day of sunlight on the panels.
This proved to be the case, since we were getting less than 1 KWH per day when we put the system in, and about 5.2 KWH per day in late April and early May. Unfortunately,without the shading, this solar system would probably cover about 7/8 of our energy usage. With the shading, it covers a little over half. Still, to me it is worth it. Our DIY solar system is drawing significantly less off the grid. Overall, our journey into installing our own solar system has been an incredibly rewarding experience.
Used with permission. © Home Power, Inc.