Your Ideal Offgrid New Construction Setup

Consumerbot3418 said:

Having been off-grid for about two years now, I’ve learned a lot of lessons.

If you have a frugal mindset, you might find yourself constantly worrying about “wasted” power when your solar batteries are fully charged. Or you might stress about avoiding the use of generator power during shortfalls. It seems there’s constantly either too much power, or not enough. It's a source of constant frustration for me, which I need to learn to be at peace with. Power will inevitably end up being wasted on sunny days, and I will end up burning diesel on dark winters days. My desire to optimize means I'll never be satisfied...

Another significant lesson I’ve learned is the importance of having solar arrays pointed east and west. While a south-facing orientation maximizes yield for grid-tied systems, off-grid setups benefit more from capturing power earlier and later in the day.

My 2¢, hope it helps.

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I ran this through PVWatts with the "hourly" csv for my location. Basically a 10kwh system facing due west and 10kwh system facing due east, vs a single 20kwh system facing due south. All were 35 degree tilt (and maybe that's the flaw?). What the numbers gave was that production was about 10% less overall for the East/West system, but quite a bit better 6-8am and 4-5pm in the summer, as expected. But what was unexpected was when looking at winter numbers, the due south system actually produces better in early morning and late afternoon; and winter is what most off-grid are trying to maximize.

I did the same calculation with 10kw facing 135 and 225 degrees (90 degree angled V of panels), and it was better, but same deal. 20kw due south beats 10/10 facing due SW and due SE in early/late hours in the winter, the 10/10 beats in early/late hours in the summer.

Obviously, its only a calculator, but its a tool many rely on. So I'm wondering from actual real-life experience - is that just flat out wrong? Is the East/West panel recommendation specific to certain seasons or certain latitudes? Are certain tilts recommended?

CVCPJared said:

I ran this through PVWatts with the "hourly" csv for my location.

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I've done the same with PVWatts for my location in Maine (~44.5 longitude) and spent a lot of time staring at the sky as well. I've come up with the same conclusion for maximizing winter production: Face 'em all due south! There's just precious little sun to the east or west from Nov - Feb. In June-July I could get massive production facing east or west, but not so much in winter, when I need it. There's a guy on YouTube in the midwest US who tried various azimuths, collected and plotted out the data over a year, and reached the same conclusion. If he had infinite ability to add panels he could maximize production with more east & west panels those extra strings would help. But for most of us with only so many panels and so much room, south is your best bet.

Madcodger said:

Wood boilers (commonly outdoor, although indoor units also available) are wonderful beasts, but they consume very large quantities of wood and require care and feeding 2-3x per day. This is not the same as putting a couple of logs in the woodstove, but more like putting a day's worth of woodstove wood into the boiler at each "feeding". And unlike a woodstove, you can't generally just let them go out and sit unattended for days or weeks if you decide to go away for a winter vacation because you have this pesky tank of water (and pipes) surrounding the boiler, and it can freeze.

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I'm always surprised reading this from our friends in a cold climate across the ocean. Over here most, if not all, of the wood boilers are indoor units (I've never seen an outdoor wood boiler here). These nowadays tend to be highly efficient gasification units. They are also coupled to a large buffer tank (mine is 3000L), and you make one fire a day on the coldest of winter days (and otherwise a fire every other day or couple of days) and store the energy in a buffer. The wood boiler burns the wood as hot and efficiently as possible, and there is no need to add any wood or keep the fire going.

Most, if not all, systems are also using a glycol mixture so you can leave them go cold in winter without issues and all you need to do if you are away for extended periods of time is flush the hot and cold water pipes. The tank, boiler (and floor heating) are a closed glycol system, the hot domestic water is taken from the buffer with a heat exchanger (copper coil).

I also have an air-to-water heat pump hooked up to the same buffer, and this means I have to burn less, if any, wood in spring and autumn periods where I need heating and hot water, but still have plenty of sunshine as well. Since these units are self-contained (monoblock), it's simply hooking up two pipes to the buffer tank. I bought my 8kW heat pump for under 2k Euro and installed it in a few hours.

@mecdatlanta and others, this is my heating set-up with the details:


My heat pump is mentioned in this entry:

CVCPJared said:

I ran this through PVWatts with the "hourly" csv for my location. Basically a 10kwh system facing due west and 10kwh system facing due east, vs a single 20kwh system facing due south. All were 35 degree tilt (and maybe that's the flaw?). What the numbers gave was that production was about 10% less overall for the East/West system, but quite a bit better 6-8am and 4-5pm in the summer, as expected. But what was unexpected was when looking at winter numbers, the due south system actually produces better in early morning and late afternoon; and winter is what most off-grid are trying to maximize.

I did the same calculation with 10kw facing 135 and 225 degrees (90 degree angled V of panels), and it was better, but same deal. 20kw due south beats 10/10 facing due SW and due SE in early/late hours in the winter, the 10/10 beats in early/late hours in the summer.

Obviously, its only a calculator, but its a tool many rely on. So I'm wondering from actual real-life experience - is that just flat out wrong? Is the East/West panel recommendation specific to certain seasons or certain latitudes? Are certain tilts recommended?

Click to expand...

Madcodger said:

I've done the same with PVWatts for my location in Maine (~44.5 longitude) and spent a lot of time staring at the sky as well. I've come up with the same conclusion for maximizing winter production: Face 'em all due south! There's just precious little sun to the east or west from Nov - Feb. In June-July I could get massive production facing east or west, but not so much in winter, when I need it. There's a guy on YouTube in the midwest US who tried various azimuths, collected and plotted out the data over a year, and reached the same conclusion. If he had infinite ability to add panels he could maximize production with more east & west panels those extra strings would help. But for most of us with only so many panels and so much room, south is your best bet.

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Try changing the tilt angle for winter production in your different tests? Having ground mounts that you can adjust throughout the year will help your winter production the most. https://www.solarpaneltilt.com/

There are a lot of reasons a full off grid install might prefer some slightly east/west panels. Like someone else said before you are effectively lowering your peak watts in the middle of the day and spreading it out during the rest of the day. This is helpful if you are routinely wasting power when your batteries are already 100%. So you could come out ahead in a situation like this. But with no obstacles or weather considerations, south facing panels will theoretically always come out ahead.

But even if you are not wasting power, your local weather can have a big effect on your production. So some panels facing more west and some panels facing more east can hedge your bets against weather or clouds affecting the middle part of the day. And if you are off grid, losing some yearly production to possibly gain some production on poor weather days is a good trade off.

Madcodger said:

But for most of us with only so many panels and so much room, south is your best bet.

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I think OP is in GA, which is going to be different from Maine.

In my location (probably GA, too), AC in summer is actually trickier than most winter days. (Another lesson learned—had made it through winter and thought the hard part was over!)

My largest array is due south, but the smaller east array has saved the day over and over, producing substantial power hours before the south array starts kicking in.

If I could only have one array, then south. If only two, I’d probably aim one array SW, and another SE. Three is probably best: one E-SE, one south, one W-SW. The east/west arrays can probably even share the same MPPT.

SolarFlares said:

And if you are off grid, losing some yearly production to possibly gain some production on poor weather days is a good trade off

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Well explained, thanks.

More south panels means a bigger midday peak, and counting on clear skies during that time period.

A more spread out power curve is not only hedging bets on weather, but also easier on batteries, since you lessen the peak charge current. And as a consequence of that, you can have more PV per watt of charge/inverting power.

upnorthandpersonal said:

I'm always surprised reading this from our friends in a cold climate across the ocean.

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I love my country, but we could learn much from others. Our history of abundant energy in decades past created bad energy habits that continue. Our approach has been to just dump huge volumes of energy into the equation, with little emphasis on conservation. As a result, we end up with only a limited set of options when it comes to equipment and those who might want to install it.

upnorthandpersonal said:

I bought my 8kW heat pump for under 2k Euro and installed it in a few hours.

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Well, that makes me envious! Air-to-water heat pumps are still rare in the US, and incredibly expensive. We (sadly) still much prefer to burn things (mostly fossil fuels) to make heat. In our rural area, the largest HVAC installer just told me they currently have no one trained to work on air-wter units as he was speaking to me to prepare a quote for our new system. So, we'll end up with a propane boiler for the hydronic and air-air mini-splits for cooling and shoulder season heat, and I'll quite possibly end up trying to install my own air-water unit and a larger buffer tank in a few years, when hopefully we have some selection and lower prices, as is now the case for air-air units (but only recently).

Consumerbot3418 said:

My largest array is due south, but the smaller east array has saved the day over and over, producing substantial power hours before the south array starts kicking in.

If I could only have one array, then south. If only two, I’d probably aim one array SW, and another SE. Three is probably best: one E-SE, one south, one W-SW.

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Well, forums are designed in large part for debate... I respect your opinion and you make some good points, but I can't say I agree, at least for everyone, on everything. I considered the E-SE/S/W-SW "fan" approach as I was designing my system, but the math didn't work as well for me as a south-only approach. So, depending on one's needs, location, and battery capacity, I'd encourage anyone to spend time on PVWatts figuring it out for themself.

A big part of the calculation can depend on battery capacity. If you are topping out by early afternoon but then using much of that stored energy as the day continues, a west-facing array can certainly be a game changer. The same can be said for an east array if you have a battery system that has given up much of it's energy overnight and now needs to be fed. But if you aren't generally going into or out of the night with huge worries, and can go for several days on battery alone, I respectfully suggest that planning for total monthly production is a good guide (along with a good generator for the stretches of no sun, when it all becomes moot, of course).

Madcodger said:

Well, forums are designed in large part for debate... I respect your opinion and you make some good points, but I can't say I agree, at least for everyone, on everything.

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Perhaps I should’ve shared my experience with the caveat that it may not apply to everyone? It’s just what I’ve found to be true in my location, with my system. YMMV.

Madcodger said:

But if you aren't generally going into or out of the night with huge worries, and can go for several days on battery alone, I respectfully suggest that planning for total monthly production is a good guide

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I can easily go several days on battery in winter. Summer is different. With highs over 100° day after day, overnight lows in the upper 80’s, and 90+% humidity, air conditioning basically becomes a requirement, and the biggest energy drain. The same batteries that easily last several days in winter can barely eek it through the night, and east/west arrays are a game changer.

Perhaps as battery storage gets cheaper, it’ll make sense for me to over provision (even further) on batteries, and point all panels south.

From a financial perspective, I’d rather get as far as possible on minimum batteries right now, as prices continue to drop, and advances appear on the horizon.

I do appreciate the food for thought, and counter perspective. I hope this discussion has been beneficial for OP.

Consumerbot3418 said:

I can easily go several days on battery in winter. Summer is different. With highs over 100° day after day, overnight lows in the upper 80’s, and 90+% humidity, air conditioning basically becomes a requirement, and the biggest energy drain.

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I mean from what I saw on PVWatts, if Summer is the season you are the most short of electricity, East/West makes perfect sense. Everybody has different environments and different needs

We've had a few days at 113 this summer already, but even then it cools down to high 60s/low 70s at night. We use more electricity in the summer but also generate much more, so it evens out