Feast or Famine, The off grid solar dilemma.

[Mattb4]

Designing an off grid solar solution always seems to end up being a feast or famine situation. You either have more potential than you can use or you fall short of having enough due to battery capacity, Season, weather or unexpected loading. There is no question that the AIO's have helped with this by being able to utilize the grid (or a generator) to make up for shortfalls but since excess can not be sent to the grid for later use, or a compensation payment amount, PV production has to sit idle. Those people that are grid tie never encounter this since they upload to the grid whatever their panels produce in excess of house loads.

You see many folks trying to find a use for extra PV capacity by either manual load addition or automatic dump loads. Other folks add more battery storage so that they can go longer between PV production intervals. Most of the solutions bring their own problems. One being if you get dependent on the "dump" load you added than the times of lower PV production puts you further in the hole. In the case of added battery storage you can reach the limit of not having enough PV to charge back up your battery in a reasonable time frame if it gets drawn down too much. More PV than puts you back into a possible under utilized potential.

My latest setup allows me to manually transfer a hot water heater on if I see my batteries charged by midday. Or I can switch a window AC to run.

Curious of how other off gridders handle the feast and famine times.

 

[SeaGal]

I'm not off grid, but don't gain from exporting much... so no issue with the famine, but when I have a feast I get more washing and drying done ?

 

[SilverbackMP]

Point of order. Folks were using auto start generators and the grid well before AIOs. My parent’s 25 year old Trace had relays for generator auto start.

 

[OffGridInTheCity]

I'm off-grid w/grid-assist. No plans for grid-tie.

Originally, the main goal was to consume 100% of PV production and live comfortably with some conservation. This has been achieved for 8 months of the year with 14kw of PV. It's the 3-4 months of winter that are dismal - only 30% of minimum needs.

The last couple of years I've been enhancing the PV and battery and have come to terms (in my mind) with some wasted PV in spring/early-summer for the sake of better winter results. But even so, I have an unused hot-tub as a dump potential etc.....

I'm gradually adding another 4kw of active PV. I also have 10kw of 'emergency panels' stored under the house to temporarily deploy to the back yard in a 'huge emergency in winter'.

Bottom line - I'm OK wasting up to 30% of PV in spring/summer to get up to 50% of needs in winter. It's been a gradual, mental process for me as the realities have become clear over the last 5 years of actively producing power.

 

[Mattb4]

Point of order. Folks were using auto start generators and the grid well before AIOs. My parent’s 25 year old Trace had relays for generator auto start.

Well sure. Just like our primitive forebears used campfires for heating versus our modern HVAC.

 

[rhino]

Well sure. Just like our primitive forbears used campfires for heating versus our modern HVAC.

Outback as well has had inverters that could do this for 15+ years now. Auto generator start, grid backup, grid charge, sell to grid, etc..

 

[OffGridInTheCity]

Point of order. Folks were using auto start generators and the grid well before AIOs. My parent’s 25 year old Trace had relays for generator auto start.

From a prepper stand-point, solar panels don't need fuel. It takes significant fuel/generator to create 40kwh/day as in 40kwh * 120days of winter = 4,800kwh / 5kwh per gallon = 960 gallons of fuel for just 1 winter. Storing 1,000gal of fuel is just not realistic in my city/neighborhood.

 

[Adam De Lay]

Curious of how other off gridders handle the feast and famine times.

Right now when I see a "feast" coming, I'm frantically running around the house figuring out what extra things can be done. Dishes, laundry, etc. Trying to use all the potential possible while ensuring my batteries are full.

So how are you dumping power to the water heater?

 

[Mattb4]

My water heater has a switch for on/off and is fed from a MTS (manual transfer switch) with power from grid or PV.

 

[MrM1]

My water heater has a switch for on/off and is fed from a MTS (manual transfer switch) with power from grid or PV.

I'm doing water heater on grid / off grid via a Double Pole Double Throw contactor with a 120v control that I automate through a smart home receptacle.

Further, when the water heater is off grid it only heats water when the battery is 60% and above through another contactor and the midnite solar classic 12v automation feature.

 

[KITROBASKIN]

You know how some rich people have money sitting around? Well some of us are rich in solar panel generation capacity. Life is good. Gratitude.

 

[hwy17]

Point of order. Folks were using auto start generators and the grid well before AIOs. My parent’s 25 year old Trace had relays for generator auto start.

I'll double down on that. Delco Light Plants had auto generator start and stop in 1929.

 

[SparkyJJO]

If I was off grid I'd just expect to build out to cover the winter, and excess in summer is just that, excess. It can help run the AC. Charge up the battery powered zero turn mower. Maybe I'd come up with something fun to use the excess power for during the summer. Don't know. But if it got "wasted" well ok then. Am I "wasting" sunlight that I'm not collecting on solar panels? Hm. Not really...

 

[SilverbackMP]

Well sure. Just like our primitive forebears used campfires for heating versus our modern HVAC.

I would take a good 25 year old Tace/Xantrex system over almost all Chinesium crapola that’s now being flogged. Yep. More trust in the old reliable.

No trust in the EG4s and Growatts and all of that kind of crap lasting anywhere close to that long (not to mention the excessive ghost loads from the inverters themselves).

That’s kinda of a critical thing when there’s no Ameren UE, PG&E, or Duke energy to call to come fix you sh!t.

 

[SilverbackMP]

Outback as well has had inverters that could do this for 15+ years now. Auto generator start, grid backup, grid charge, sell to grid, etc..

Yep, the folks that developed and created Trace sold it to Xantrex. Which in turn sold to Schneider (even kept the same color scheme and ascetics through all of that).

Then the original Trace folks started and developed Outback. And later sold that and started Midnite. And I think Magnum might have its roots in all of that too.

 

[dougbert]

I'm off-grid w/grid-assist. No plans for grid-tie.

Originally, the main goal was to consume 100% of PV production and live comfortably with some conservation. This has been achieved for 8 months of the year with 14kw of PV. It's the 3-4 months of winter that are dismal - only 30% of minimum needs.

The last couple of years I've been enhancing the PV and battery and have come to terms (in my mind) with some wasted PV in spring/early-summer for the sake of better winter results. But even so, I have an unused hot-tub as a dump potential etc.....

I'm gradually adding another 4kw of active PV. I also have 10kw of 'emergency panels' stored under the house to temporarily deploy to the back yard in a 'huge emergency in winter'.

Bottom line - I'm OK wasting up to 30% of PV in spring/summer to get up to 50% of needs in winter. It's been a gradual, mental process for me as the realities have become clear over the last 5 years of actively producing power.

this is me, my model as well

9kw of PV, in Utah, April to Oct now I am effectively "off-grid" in that the grid breaker is in the OFF position. Last winter was a winter where I used more grid assist than the prior 3 winters. One cause was the 3 weeks that took me to swap inverters from a 120v only to a 240v XW Pro. From Sept of 22 to the End of March 23, I had to buy 1840 kwhs, which in reality is only 2 months of energy consumption in my house

I have a dual set of 50 gallon electric water heaters which is my diversion load for when the battery is full. this occurs mostly in the summer period.

I like the idea of 10kw of stored panels for a winter deployment, I will ponder that.

Panels are so much cheaper today than in 2000 when I deployed my first 12 100 watt panels. Each cost $475 to $500 at that time. Having extra panels to "waste" no longer hurts like it use to. they still product 50 to 60 watts now, and I just sold them for $10 each to a friend for him to start playing wit solar

thanks for your report

 

[dougbert]

I would take a good 25 year old Tace/Xantrex system over almost all Chinesium crapola that’s now being flogged. Yep. More trust in the old reliable.

hey I have a Xantrex SW+5548 sitting idle (my last inverter) and am pondering to keep or sell

 

[SilverbackMP]

hey I have a Xantrex SW+5548 sitting idle (my last inverter) and am pondering to keep or sell

I’m keeping our old stuff. Not much money in selling it and you never know when you might need it. Mishmash of Trace and older Outback.

 

[OzSolar]

It's been years since I designed and installed an off grid system with more than one day of battery storage and it's worked out just fine.

It's an interesting quandary that I can only guess at. Unfortunately I don't have any hard numbers to back it up but my 30+ years of experience of designing, building and maintaining a few hundred full time off grid systems my humble opinion is that most are much better off with the simplest possible set up. From what I've seen the more money you spend thinking that you're enhancing resilience adds needless complexity and ultimately leaves you in a worse place with a far more expensive system that no one can fix.

It's the classic but ironclad 80/20 rule. 20% of the effort (and or cost) will get you to within 80% of ideal. Any attempt to make a dent in the remaining 20% is very time consuming and expensive.

 

[time2roll]

It's the classic but ironclad 80/20 rule. 20% of the effort (and or cost) will get you to within 80% of ideal. Any attempt to make a dent in the remaining 20% is very time consuming and expensive.

Is it realistic to just do without during difficult times? People did get by without electricity at all and not that long ago.