(Continued from Part 1.)
Question: How is my system size being determined?
Question: How many hours per day of power production will I have?
Here is where a little ‘art’ comes into all this ‘science’. Panels come in a few different sizes, usually around 325 to 425 Watts. The most common seems to be 400 Watts of generation. What they try to do is balance your usage with the size of panels. In the above case, it would take about 50 panels @ 400 watts per panel to equal the 19kW system (actually 20, but that is where the ‘art’ comes in).
BTW, this would be a huge array. Not something likely to fit in your backyard, and unless you have a much larger house than I’m familiar with, it probably wouldn’t fit on your roof either. I’m using round numbers for demonstration purposes. My actual system is a 16kW system of 40 panels and it still is about 60 feet long and over seven feet high. (See photo.)
I took you through that so you’d understand the basic process, but also to show the flaw.
First, most of you may have noticed. This means the solar array is only offsetting your power consumption for 6.5 hours per day. The rest of the day – and night – you are still relying on grid power. Not only that, you may still be without power when you need it most. I’ll come back to this topic in the Storage section, in Part 4.
The catch is that you also don’t want to over-produce. Depending on the agreement you have with your grid operator, they may charge you a distribution charge if you produce more than expected and send it back to the grid. Remember, their systems and distribution network is designed to provide electricity for your neighborhood, so they built infrastructure to support that. If you start overwhelming that infrastructure by sending a lot more energy than the system can support, they will have to upgrade. This costs money and since you’re essentially the cause and you’re sending more than they expect, you get to pay for it.
Question: Will I be over-producing and what will that cost?
Net Metering
One of the greatest benefits of ‘going solar’, with just panels is called “net metering.” Maybe it is called that everywhere, but that is its name, locally. This is where you generate more electricity than you use (say the extra 1kW for 6.5 hours in our example, leads to 6.5 kWh of over-production). This electricity is sent back to ‘the grid’ and the grid provider gives you credit for this generation. That credit is then applied to your electric bill. This means that you not only save while you are producing and not taking in power from the electric company, but you are also offsetting the cost of the electricity that you do use.
Please note that I am using the terms ‘grid provider’ and ‘electric company’ to denote separate entities. In my area, and yours may be different, we have a state-wide grid provider (Oncor) as well as local power generation companies. Most of the local companies are cooperatives, or co-ops (member-owned, smaller companies). Co-ops are usually the power generation company as well as the sales company. Oncor generates most of the power and maintains most of the electrical distribution in the state. Then we have electric companies that resell the power generated and distributed by the grid provider. For me, the grid provider enters into the agreement for energy generation and gives ‘permission to operate’ (PTO) a power generation station. The electric provider offers plans that may or may not compensate you for your excess generation. Where there are coops locally, many do not offer net metering nor do they offer plans to buy back customer-generated power.
Many people have been able to offset their entire electric bill using net metering. Unfortunately, this is becoming less available. Many electric companies are now only offering a reduced rate for the power you generate versus the power you consume from the grid. Some companies also allow you to apply the over-production credits to your base customer fee (the one they charge you just for being a customer) whereas others do not. The end result is that whether you can offset your electric bill with grid-tied solar depends on many factors; some of which you can’t control.
JWR Adds: For preppers, there are some huge drawbacks to grid-tied PV power systems. One of the biggest is increased vulnerability to EMP and solar flares. Those many miles of power lines are essentially a big antenna to collect EMP or Carrington Event-style spikes. The other drawback to most grid-tied systems is that they usually lack battery backup, so they do not provide true backup power, for disasters. Depending on their design, in the absence of grid power, some non-battery grid-tied PV power systems provide NO power to your home, at all. Others provide power only when the sun is shining. Be sure to research this thoroughly, before you invest in a system! A grid-tied system may not be right for you.
Question: Is net metering (or consumer-production buy-back) offered by your grid provider and / or electric company?
Question: Which electric companies offer the best Net Metering arrangements locally?
Once my system was ready to go, the grid provider had to upgrade the transformer to my house, which delayed PTO, thus delaying any buy-back agreement I could get with an electric company. Many times it won’t be known what upgrades will be required. Chances are, the newer the equipment your provider uses, the more likely you’ll not need an upgrade. In more rural areas, it is more likely upgrades will be needed. In my case, the grid provider paid all those costs, so it is more of a timing issue than anything, but it is still good to know. If there is a long delay, you could even face paying for your system without being able to sell back your over-production, again impacting your cost analysis.
Question: Are upgrades needed to the grid before I can get PTO? What are the estimated timelines?
The next consideration as far as net metering goes is whether it is actually available with the system you are considering. One company presented me with a roof-mount, (despite my request for a ground-mount) panels-only system and said I would be selling back over-production to the grid. These guys had several red flags, and I found out later that my local grid provider requires batteries on systems in order to establish net metering. Something about averaging out production spikes, etc. In the end, that meant I would have been stuck with paying full rates for all my grid power during non-production hours had I chosen that type of system. This can really change the cost equation for many people.
Question: Do I need equipment beyond solar panels for the grid provider to buy my over-production.
Check out the section on Storage later in the article for more considerations about other equipment.
output Optimization
This is probably the place where I least understood how things worked. Like I said above, I understand electricity and I’ve studied solar. I have small solar power stations (a.k.a. ‘solar generators’), and I have a solar well pump. All these things help, but they do not fully prepare you for a commercial-built solar production array.
Let’s talk basics first. When I’m recharging my compact solar power station, I consult my handy-dandy chart to determine the best angle for production. I used this site to determine the best angle for my property’s latitude, and recorded it in my notebook. It says:
Year Round Tilt Angle:
28.1 degrees from horizontal
SPRING tilt angle:
28.1 degrees
SUMMER tilt angle:
13.1 degrees
FALL tilt angle:
28.1 degrees
WINTER tilt angle:
43.1 degrees
When I go to set up my little portable system solar panels to recharge my power stations, I use those angles and get pretty close to optimum output.
It never even crossed my mind to think how my huge, 60′ long array was going to be tilted. Notice, there is a major difference between summer and winter. This is where the pros have come up with a shortcut. But this shortcut may not be best to suit your desires.
Since most people are still offsetting at least some of their electrical costs with net metering, the pros set the angle of the panels to optimize credit generation. You generate the most credits when you have clear skies and the sun is up most of the time, thus most commercial installers set the panels to optimize summer production. The consumer builds credits during the summer to offset costs during less productive months.
JWR Adds: A shallow summer-optimum angle might work well in southern states, but note that this comes at the cost of increased risk of hail damage. In northern latitudes, where snowfall is frequent, a steep panel angle is your friend. So I would advise northerners: Unless you have an easily-adjustable rack, it is best to lock it down at your winter-optimum angle. Winter is when northerners will need PV power the most.
That is a great mindset if your goal is to offset your electric bill. For many of us though, especially readers here, the goal is to be more self-sufficient. This means that you may not want to be optimized for one part of the year only to rely heavily on your electric provider during another part of the year. You (as I) may want to take a more balanced approach.
(To be continued tomorrow, in Part 3.)