Going with Offgrid Solar

[kmakar]

We've been running our house "part time" on my self designed offgrid solar setup for about 2 years now and it's worked out well. We used the solar power during the day, and at night it switched back to line power (automatically). We cut our electric bill in half and at the same time had had full time power in the event of a power outage from the power company without the need of a generator.

With the cost of LifePO4 batteries (lithium iron phosphate) dropping considerably (we had been using sealed lead acid deep cycle batteries), we decided it was time to make the jump to the new LifePO4 batteries. We also decided that the current setup of using 2 decent sized inverters (one was 6,600 watts, and the other 6,000 watts) introduced additional hurdles to overcome (by splitting out our electrical panel to use the power of each inverter to split the load), so we also got a much larger inverter (18kw with a 30ms surge rating to 54kw).

We are still waiting on 2 more LifePO4 batteries (we currently have 600 amp hours, but are adding 2 more for a total of 800 amp hours). I finished the upgrade yesterday and after the batteries get their first full solar charge today, we'll be going full time solar (flipping the transfer switch to full time solar).

I still have to design, build, and weld a steel rack to house and protect the batteries, but I just held it together with wood for now.

I did all the electrical work myself. I used to be a general contractor, so for me it's rather simple.

Here is what our setup looks like.... I was testing the loads on the new inverter last night and everything performed perfectly.

If you have questions regarding offgrid solar, I'll do my best to answer questions or help.

 

[Nashville Cat]

I have 2 sets of 16 LiFeP04 batteries coming (3.2 volts each) which make 2 - 48 volt packs of 280AH each. A total of 26 kw battery storage.
Assuming I use 50% of the storage, that's 13 kw overnight.
I hope to run a 2.5 ton heat pump, refrigerator & separate freezer and heat pump water heater. With 24 -440 watt panels and inverter to be determined ?

 

[kmakar]

I have 2 sets of 16 LiFeP04 batteries coming (3.2 volts each) which make 2 - 48 volt packs of 280AH each. A total of 26 kw battery storage.
Assuming I use 50% of the storage, that's 13 kw overnight.
I hope to run a 2.5 ton heat pump, refrigerator & separate freezer and heat pump water heater. With 24 -440 watt panels and inverter to be determined ?

I have 30.5 kWh of batteries (just ordered another 4 to make it a total of 51kWh). The best way to calculate your needs is to find out what is your normal kWh used per month from your electric bill, divide your monthly usage (heaviest usage month) by 30 (30 days per month) and that should tell you how much battery storage you'll use, but you'll also have to calculate for cloudy days too (if you plan on running 24/7 offgrid solar).

With the right inverter you can run everything in your house without an issue. If the charge on my batteries is close to 95% to 100% when the sun goes down (no longer getting power from the panels) my 30.5 kWh drops to 40% overnight (hence why I'm adding more batteries).

 

[Nashville Cat]

With the right inverter you can run everything in your house without an issue. If the charge on my batteries is close to 95% to 100% when the sun goes down (no longer getting power from the panels) my 30.5 kWh drops to 40% overnight (hence why I'm adding more batteries).

I'm going to see if I can run my 2.5 ton heat pump at first. Then I will add the freezer & fridge and sort that out. Finally adding the water heater and lights/tv/computer.

 

[kmakar]

I'm going to see if I can run my 2.5 ton heat pump at first. Then I will add the freezer & fridge and sort that out. Finally adding the water heater and lights/tv/computer.

I think I should have specified that your inverter must be properly sized to handle capacitor surge of motors starting. Even if the inverter is large and can run the 2.5 heat pump, it's the startup surge that would be the killer.

Alot of the chinese made ones have 3 times the surge for startup, so that's probably where you should look first.

I have an 18kw inverter that has 3 times the surge capability and I know it's quite oversized, but it also doesn't tax the inverter and push it to its limits. I run everything in my house with no issues (and can run everything at the same time), but it came with a hefty cost of $4,415 delivered.

 

[Nashville Cat]

I think I should have specified that your inverter must be properly sized to handle capacitor surge of motors starting. Even if the inverter is large and can run the 2.5 heat pump, it's the startup surge that would be the killer.

Alot of the chinese made ones have 3 times the surge for startup, so that's probably where you should look first.

I have an 18kw inverter that has 3 times the surge capability and I know it's quite oversized, but it also doesn't tax the inverter and push it to its limits. I run everything in my house with no issues (and can run everything at the same time), but it came with a hefty cost of $4,415 delivered.

One thing that has been a little confusing : I've read that low-frequency inverters can handle surges much better than the other types.
Low frequency inverters weigh much more usually because of the heavy copper coils that they have.
The Sol-Ark 12k inverter is considered top-of-the-line but it doesn't weigh much and it's not low-frequency.
I'm leaning toward the MPP Solar LVX6048WP which is heavy (100 lbs) and is low frequency. I would need 2 in parallel to get 15kw capacity

Overstock LVX6048WP -WaterProof UL Grid Feedback 6kw Split Phase IP 65 Outdoor rated – SEE CONDITIONS – Watts247 Wholesale

watts247.com

 

[kmakar]

One thing that has been a little confusing : I've read that low-frequency inverters can handle surges much better than the other types.
Low frequency inverters weigh much more usually because of the heavy copper coils that they have.
The Sol-Ark 12k inverter is considered top-of-the-line but it doesn't weigh much and it's not low-frequency.
I'm leaning toward the MPP Solar LVX6048WP which is heavy (100 lbs) and is low frequency. I would need 2 in parallel to get 15kw capacity

Overstock LVX6048WP -WaterProof UL Grid Feedback 6kw Split Phase IP 65 Outdoor rated – SEE CONDITIONS – Watts247 Wholesale

watts247.com

Actually that's quite the opposite. Low frequency inverters don't handle heavy loads well at all, and they are much lighter.

High frequency inverters are much heavier and usually have heavy iron core transformers which give it the ability to handle the heavy loads.

As far as your inverter selection, according to the specs posted here and on their website, it bears no surge capability and would require you to add more of those inverters in parallel to get that capability (like to start your 2.5 ton AC).

To start your central AC, the inrush amps would be about 70 to 80 amps to start your AC fan/compressor, so that calculates to a bare minimum of three (3) of those inverters (if the starting amps are below 75), but you'd really be needing four (4) of those inverters.

You need enough inverter wattage to power everything, but surge capability is just as important.

 

[cage2592]

Dang I want to go this route so bad. My problem out in the country is size of the house, well pump, septic pumps, x2 A/C units and several fridges and freezers. this doesn't include the shop. I would also ground mount the panels.

I've always heard the batteries were the most expensive and need replacing every 5 yrs.

Id be interested in your thoughts what your total cost so far is.

Its going to be either Solar this next summer or a min 32K (min) diesel generator and a 500gal tank.

Mike

 

[kmakar]

Dang I want to go this route so bad. My problem out in the country is size of the house, well pump, septic pumps, x2 A/C units and several fridges and freezers. this doesn't include the shop. I would also ground mount the panels.

I've always heard the batteries were the most expensive and need replacing every 5 yrs.

Id be interested in your thoughts what your total cost so far is.

Its going to be either Solar this next summer or a min 32K (min) diesel generator and a 500gal tank.

Mike

I live rural and have a normal sized house (1,550 sq ft with a 700sq ft garage that has AC as well), and I am about to build an 1,800 sq ft shop that will be powered by the solar as well.

Batteries are the most expensive part if you go with the best. If you buy flooded batteries, they are the cheapest, but you'll be replacing them every 3 to 7 years depending on how much you cycle them (varying depths of discharge (DOD). I recently upgraded from sealed lead acid batteries to LifePO4 and it was a major hit (total cost for the batteries was about 18k), but they will last 25 years or longer (well after I'm dead). Buying solar panels is cheap, building your own ground mounts are easy with schedule 40 steel pipe, and the remaining components are not too expensive. I originally was going to buy a whole house generator, but when I calculated the ongoing costs, it was cheaper to go solar (for me), plus there is no noise and as soon as I add the next 4 batteries (waiting for delivery), I'll be 100% offgrid not needing the power company at all. One of the big things you can do to save money is upgrade your water heater to a hybrid. That saved me at least $30 to $40 a month.

Best place to start is look at your electric bill and see your total kWh used per month and divide that by 30 and that will give you your starting point for what you'd need to run on solar. I can help with the calculations if you'd like.

 

[cage2592]

So looking at my usage over the last 12mths, highest was 2464 KWh (AUG) and lowest was 1172 KWh (Last NOV). Adding up all 12 months is 25,378 KWh / 30 days = 845.93 KWh.

We have plenty of area to ground mount any panels and would probably do it in stages if it would save money. I was thinking, just getting all the power distribution required to be completely off grid minus the batteries and mounting/running it all. Then several panels the next month with adding following panels every month until I got what is needed. Then the batteries. This would be just for this house currently. The initial power distro would need to be able to handle at a later date, the shop, in-law suite, maybe pool.

Thoughts or questions Sir.

Mike

 

[kmakar]

So looking at my usage over the last 12mths, highest was 2464 KWh (AUG) and lowest was 1172 KWh (Last NOV). Adding up all 12 months is 25,378 KWh / 30 days = 845.93 KWh.

We have plenty of area to ground mount any panels and would probably do it in stages if it would save money. I was thinking, just getting all the power distribution required to be completely off grid minus the batteries and mounting/running it all. Then several panels the next month with adding following panels every month until I got what is needed. Then the batteries. This would be just for this house currently. The initial power distro would need to be able to handle at a later date, the shop, in-law suite, maybe pool.

Thoughts or questions Sir.

Mike

First off, don't call me sir, I'm a regular guy just like you and I put my pants on the same way you do (unless you're deformed or something).

The highest bill is what you need to go by, but that begs to ask, what is causing that to be so high at 2464kWh? Your 1172kWh sounds more normal. Older house? Un / under insulated?

 

[kmakar]

So looking at my usage over the last 12mths, highest was 2464 KWh (AUG) and lowest was 1172 KWh (Last NOV). Adding up all 12 months is 25,378 KWh / 30 days = 845.93 KWh.

We have plenty of area to ground mount any panels and would probably do it in stages if it would save money. I was thinking, just getting all the power distribution required to be completely off grid minus the batteries and mounting/running it all. Then several panels the next month with adding following panels every month until I got what is needed. Then the batteries. This would be just for this house currently. The initial power distro would need to be able to handle at a later date, the shop, in-law suite, maybe pool.

Thoughts or questions Sir.

Mike

How much land do you have, and do you have clearings south and west?

 

[cage2592]

No clearings currently where id want them but do have availability and access to clear what is needed on 25 acres.

 

[kmakar]

Okay, that works. Based on the highest usage and wanting to add the guest suite and future shop, you'd need (rough estimate) forty eight (48) 440 watt solar panels (about $8,000), 4 solar charge controllers (about $2,400) to start with, then once that's done (or close to it) add the inverters, and a small bank of batteries to start. What is your goal? 100% offgrid, or emergency power only?

 

[cage2592]

Our ultimate goal is off grid. Pending costs, I was looking to do in stages. First Emergency, then during daylight hours, then phasing in the large cost of batteries over time.

You know how we are in hurricanes and random power outages in rural areas.

Mike

 

[kmakar]

Our ultimate goal is off grid. Pending costs, I was looking to do in stages. First Emergency, then during daylight hours, then phasing in the large cost of batteries over time.

You know how we are in hurricanes and random power outages in rural areas.

Mike

Piece of cake. Batteries will be your biggest expense, but you can get the cheapest for now (lead acid), and buy much better later (that's what I did to break into solar).

When you are ready, let me know and I'll help spec out what would work for you. I don't sell any equipment nor to I get kickbacks mind you, I'd just be helping you.

 

[kmakar]

Our ultimate goal is off grid. Pending costs, I was looking to do in stages. First Emergency, then during daylight hours, then phasing in the large cost of batteries over time.

You know how we are in hurricanes and random power outages in rural areas.

Mike

We can get you started with an emergency system, and grow it from there. An emergency system capable of running the well, lights, fridges, freezers, and the basics would run about $7,500.

 

[77cruiser]

Do the batteries have to be in out of cold? I'm in a different climate that you guys.

 

[kmakar]

Do the batteries have to be in out of cold? I'm in a different climate that you guys.

Batteries are best when kept at moderate temperatures (above 50 degrees and below 90 degrees). The batteries which suffer the least are lithium ion and lithium iron phosphate (LiFePO4).

Most people keep their batteries in the garage or in the basement. All batteries kept indoors should be sealed (more specifically advanced glass matt (AGM)).

 

[77cruiser]

I didn't think outside in winter up here would be ideal.