by Sarah Latimer, Survival Blog:
(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).
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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.
