by B.S.V., Survival Blog:
(Continued from Part 3. This concludes the article.)
Question: Will I have power when the grid is down?
Question: Can I get net metering with a solar-only system, or do I need storage?
Battery size
With all the information above, you will be better situated to properly size your storage system. Just be aware that (unless you’re in a totally different socioeconomic class than I) you probably won’t get all the storage you want. I started off with the idea that I wanted to be three-days independent of the grid. When I found the cost of that, I scaled back. I couldn’t do it within my financial constraints. So I had to determine if it still made sense to go solar, or if another solution would be better for me. A whole-home generator would have allowed me to have the backup capability for less overall cost of equipment and installation. However, I would then have had the cost of that system as well as my usual electric bill, plus the upkeep, maintenance and associated fuel costs. For me, solar still made the most sense. However, it is important to step back from the excitement of ‘doing something’ to check whether your ‘doing the right thing’.
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Question: Now that I know what I know, is this still the right decision to meet my goals?
Charge Profile
There are so many different systems with so many different options that I can’t discuss even a fraction of them. I’ll focus on a couple of items that I think most reading this would be interested in.
First, let’s focus on how the battery is charged. Again, I am using the offset from my electric bill to pay for the system. This means reducing my draw from the grid as much as possible. In the early days, I saw that my batteries were drawing from the grid to recharge when there wasn’t enough solar to do the job – such as overnight. This is great for backup as it helps ensure that you always have ‘juice’ in the batteries, but it is not great when trying to reduce your draw from the grid. Check to make sure your charge profile is working to meet your goals. I only want solar to charge my batteries and not the grid.
Remember when we were talking about inverters above? Inverting DC into AC comes with a loss. So does changing AC into DC. So, when the grid charges the batteries, you lose power that you’re paying for and then when the batteries discharge the DC and convert it back into AC for the house to use, you’re losing power again. For me, that ended up be about 50 watts in both stages during prime usage periods. So it was like having a 100-watt light bulb going all the time. Not a huge draw, but if you can allow the grid to go straight to the house, then why waste any power on the conversion?
Question: Is the way the batteries are recharged optimized for my goals?
Second, think about how your batteries are discharged. This really will heavily depend on your goals. If you want the batteries set up as a standby system, so you always have emergency backup even in the early morning after a long dark day, you may not want your system to power your home at night. You may want to switch over to grid power at night and use your daily produced credits to offset the cost. Then you have to think about the cost of that backup system sitting there and not helping with cost savings during other periods.
