June 13, 2020

Solar Project: How's It Going?

Our solar project was to put my freezer and a small chest refrigerator on solar energy. We started with the freezer (last January) and added the fridge toward the end of March.

My freezer and upright chest fridge on our back porch.
The fridge was converted from a freezer—how to here.

Since getting both appliances off the grid, we've gotten two electric bills. We're now averaging 11 kWh per day. To put that into perspective, back when we used the HVAC for heating and cooling, we averaged about 25 kWh per day. After we quit the HVAC in 2015, our average usage dropped to 18 kWh per day. Until now. 😎 I'm excepting our numbers to go up during summer because we rely on ceiling and box fans for cooling and to keep air circulating in the house. Plus, I use my electric stove more in summer for canning.

The other thing we've been curious about is how long our battery bank will last during a string of cloudy days. We've had a lot of those lately, which has given us the opportunity to answer that question. The battery bank lasts pretty much as long as I calculated—about two days. But the panels still produce at least some electricity on cloudy days, and our charge controller optimizes that, so I can't simply count cloudy days. I have to keep an eye on the battery bank to make sure we don't drain it too low.

One method to monitor the battery bank is by the batteries' state of charge (SOC). Technically, this refers to the specific gravity (i.e. chemical composition) in each battery cell, but bank voltage gives an approximate idea of what's going on. This varies by battery type and manufacturer, so my figures are pulled from our battery user manual.
  • 100% SOC is 12.73 volts
  • 90% SOC is 12.62 volts
  • 80% SOC is 12.50 volts
  • 70% SOC is 12.37 volts
  • 60% SOC is 12.24 volts
  • 50% SOC is 12.10 volts

The SOC is measured when the batteries are neither being filled nor powering something. So the best time to get the most accurate reading is at night when neither appliance nor cooling fans are running. (The charge controller, inverter, and battery box vent fan all draw their energy from the batteries too.)

About 10 a.m. on a partly cloudy day with the inverter fan running.

Typically, folks say not to let the batteries drain below 50%. However, they will last longer if not drained even that low. I keep my eye out for 12.4, which is about 75% SOC. If the voltage is that low at bedtime when nothing is running, then I turn the inverter off for the night and wait for the batteries to refill the next day. A refrigerator is said to keep things cold for 24 hours with no electricity, and a freezer for 3 days. So as long as I don't open them, I have a time window to work with. If it's darkly overcast the next day and the panels aren't putting out much, I plug the appliances back into the grid. They are on a power strip, so if I need to plug into the grid it's easy to do. If the grid is down, well, then I have to move on to plan B, just like everybody else.

So far, we've had one power outage this spring due to high winds. I was so thankful my freezer and fridge were still running.

Things that help us get the most out of the system.

1. Adjusting the panel array angle to get the most sun.

We've been adjusting the array angle every two months. This enables us to take advantage of the sun's seasonal position in the sky and make the most electricity we can. (How we do that in this post, "Adjusting Our Solar Panels.") Here it is for June -

Array angle adjusted for early June.

Here was the angle for January -

Array angle adjusted for late January.

Quite a difference, isn't it?! Makes me glad we abandoned the idea of installing them on the roof, where they would be pretty much fixed. For quick angle adjustment in the future,  I've been marking the channel strut with the number of the month by the slot.

Positions marked for June and April.

2. Something else that helps is keeping an ice bottle in the fridge. It's a two-quart juice bottle, and it takes days to defrost, which helps keep the fridge temperature cool.

The interior must be wiped out occasionally because of condensation.

I know several of you were curious as to how this was working out, so there's my report. I hope I covered everything you were interested in. If not, just ask. For anyone interested in the whole story, it starts here.


tpals said...

Thanks for the update. Very informative.

Michelle said...

The only other thing I'd be interested in is a calculation, based on the energy you're saving per day, of how long it will take for the total investment into your solar set-up to pay for itself, even though I know cost savings isn't your only focus.

Leigh said...

Thanks tpals!

Michelle, it depends on how you look at it. I look at it from a food savings perspective, because that's why we installed the system. Because we grow and preserve a lot of our own food, that's a huge food budget savings.

Total cost for the system was about $2800. If I estimate that it saves us $400 per month on food, then it will take about 7 months to pay for itself. (That would change depending on how I calculate my food budget.) If we looked at it from a straight cost perspective, it will take longer. My electric bill for the past two months was $49 plus change. This time of year is the lowest we usually see, so if I use that for my example, then it will take a little over four and a half years to pay for itself. Our actual average will be a little higher for the reasons mentioned above, so realistically, it will take a couple months less than that.

daisy g said...

Very interesting. Solar is on my wish list. Sounds like it's worth the investment.

Sam I Am...... said...

Very interesting and I especially like the "heads up" about roof vs. ground install since the roof would be fixed, as you say, and not be able to be adjusted based on the angle of the sun.

Mama Pea said...

Leigh, I'm curious to know how you are getting along with your chest type refrigerator. Do you find it large enough for your needs and how about the convenience of the everyday "getting at" the items you want? When I look at all that I keep in my upright refrigerator in the kitchen (that is all refridge, no freezer) PLUS the second/spare refridge we have in the entry room, I wonder if I'm fooling myself thinking I couldn't function with the size space you have in the upright refridge. I know you cook from scratch (more needed ingredients) and have the milk from your goats . . . I need the space for kefir, kombucha, yogurt, extra eggs, pot of leftover soup, vegetables, on and on. (Slightly off topic of this informative post, but I keep wondering.)

wyomingheart said...

Great update, Leigh! I was very curious about off the roof installation, and your update has me rethinking some things. The frame that you have mounted your panels on, is really beefy, but we have such strong wind currents at the top of the ridge...it’s concerning. Have you experienced much wind since the installation, and if so, how did it do? I know there must be some very awesome peace in having the freezer running while in a power outage, which I look forward to experiencing! Thanks for the informative post, and get a good week!

Leigh said...

Daisy, I think it was worth the investment. Peace of mind for food storage is priceless!

Sam, I'm sure there are ways a roof-mount array could be adjusted, but I'm guessing it wouldn't be much of an adjustment and it wouldn't be easy (or cheap). It would mean climbing up on the roof to make adjustments, or installing some expensive techno-gadget to push-button adjust it from in the house!. Maybe someone who does it will share their experience with us.

Mama Pea, the chest fridge is an adjustment. For one, I really miss that extra freezer space from the old upright fridge. I'm having to rethink what I can store in the freezer, prioritize, and make adjustments.

Concerning size, I wish I could have gotten the next larger size (7 cu ft) rather than the 5 cu ft model we have. It was an issue of room. The lifting of containers to get to bottom layers is a nuisance, so I try to use that as my storage area for bulk grains, seeds, etc.; things that I get out less frequently.

The hardest thing right now is that I don't have a table immediately next to it to set removed containers on. I don't like setting them on the floor, because this is our porch, and we do track in a lot of dirt. I have a small folding cart with wheels I may set up for that.

So there have definitely been adjustments and relearning of habits. Even with all that, I'm still glad we went this route.

Wyomingheart, yes, great peace of mind! And yes, high winds are a concern, although we probably don't get them as often as you do. We get them on occasion, usually early spring. They are the reason we didn't put the panels on a pole rack. Dan made his rack stout and heavy for that reason.

This spring we had several tornado watches, with winds knocking down trees and branches, and blowing away all sorts of stuff that wasn't fastened down. The panels were fine, however. I think one thing that helped is our row of Leyland cypresses along the road front. They act as a windbreak. If you know the direction most of your wind comes from and can determine the way solar panels would need to face, you probably could plant a strategic windbreak as well.

Kelly said...

Looks and sounds like it's working really well for you! So far, we've been very pleased with our solar set-up, too. As large scale storage cells improve, we might look into getting off the grid at some point, but for now we're happy with what we have.

Leigh said...

Kelly, that's good to hear. We'd love to expand ours someday too, but for now, it's a blessing as it is.

Toirdhealbheach Beucail said...

Thank you for the update Leigh. Sounds like it was a very reasonable investment and will "pay for itself" rather quickly (arguably, anything that has allowed you to stay off the grid has already paid for itself).

The movable panels are genius. I am surprised these are not contemplated more as they would make solar more feasible.

Leigh said...

TB, my guess would be the number of panels may make it difficult to put them anywhere else but on the roof. It's common to see 20 panels or so on a rooftop, which is a lot of panels. On the other hand, if the angle is fixed, then more panels are required to make up the difference for not being adjustable. Most systems are calculated for winter, with least amount of sun. I assume contractors know how to factor in more panels for the angle of the roof. If I was doing it myself and had to have a fixed angle, I'd probably aim for the angle needed on the equinoxes. Then we'd get maximum production at least twice per year!

Cockeyed Jo said...

As it stands right now I only go into my freezer once a week to "shop." so your schedule sounds doable. My refrigerator is another story. On average every two hours especial in hot weather. As far as freezer size goes, I always err on the too big rather than too small. I kept my 27 CU Ft freezer for a decade after I became an empty nester.

Leigh said...

Jo, a 27 cubic foot freezer sounds fantastic.

Ed said...

Solar energy is getting better and easier to use but I think it still falls into the realm of best utilized by the tinkerer type. I'm hoping perhaps in my kids lifetime it will become as common as filling up a gar with gas is now.

Retired Knitter said...

One additional savings I don't think was mentioned was - you guys installed this yourself. While most of your readers probably would/could install a system themselves (because homesteading requires a do-it-yourself mind set generally) - most of the world that does have this or a similar system - pay for someone else to install - adding to the initial cost. Very interesting post.

Leigh said...

Ed, it does seem to be getting more common. and there is a learning curve, whether one DIYs or hires a commercial outfit to do it. It also requires lifestyle changes, another part of the learning curve! If it became more affordable, I think more folks would do it.

Leigh said...

RT, yes, good point. Hiring someone to install the system hugely ups the cost. More people probably fall into that category than the DIY group.

Phantomrijder said...

What a great post Leigh. Thanks so much for all the input and time it has taken to make it. It helps all us readers so much. It saves us having to discover for ourselves what you and your's have found. We live in SW France on 2ha, south facing on a hill - ideal for solar. Your post added to our enquiry into solar and what we could do to reduce our environmental footprint. Our house is 350 years old and our property is all you would ever think of idyllic France. We have a well, stables, grow our own and so on. Your investment was modest, we loved your way of getting to include in pay-backs, your savings on food. Fundamentally though isn't it not about pay-back? It's about living responsibly. That's where we are. And we know that's where you and all your readers are. Well, we will continue to look at our priorities; deepen the well, start with alpacas, solve moles tunneling and undermining us and then, with all your good post in our minds ... start on solar.

Mike Yukon said...

Thanks for the update. It sounds like your solar plan is working perfectly. I'll bet it feels good to not have to be dependent on grid power for the all-important frozen/refrigerated food storage. A few more panels and batteries and you will be off-grid entirely. Happy days for sure! :-)

Leigh said...

Phantomrijder , you're welcome! I hope everything I write about is an encouragement to others with similar goals. Your place in France sounds fantastic; like an ideal set-up. I love the idea of alpacas!

I agree, going solar (or any homesteading decision) usually has several reasons behind it. I thing that's a good thing, because it's expensive and there's a lot to learn. So it takes a level of commitment to see it through. If you ever have any questions about your own going solar, please ask. I'm far from an expert, but I'm always happy to encourage.

Mike, actually, we have two more panels the same size. :) And I wish we had a larger battery bank, but we bought as many batteries as we could afford! We continue to cut back our use of grid electricity, so who knows. Maybe someday we can make the full transition.

Chris said...

Another project paying off, although not without it's challenges in the operations dept. This is great food security, and utilising natural resources to save money on energy consumption. A win-win. Thanks for the update.

Leigh said...

Chris, it's a relief to have it working out so well. I'm amazed at how much electricity we make in summer. Not so much in winter, but it's enough, so we count this project as a huge success.