First timer - Thinking about 30,000 kwh ish system!

[SoloCon]

Hello there! I'm in the great state of Arizona and looking into a DIY ~30,000 kwh ish system.

I'm basing my system usage off my last 3 years of elec use with APS (power company here in AZ). As seen in image one, I used 29,189 kWh's between 2019 and 2020. Between 2020 and 2021, I used 26,183 kWh's. This was in a older home (built in early 2000's), 2 story home with about 2600 SF in Phoenix AZ

I recently built a new home here in Arizona and so far for 2021--2022, I've used 14,205 kWh's (9 months of the year so far, with the hottest months of the year just ahead of us)

My new home is about 2500 SF, single story. I don't have any shading on my rooftop. I do plan to add an RV garage here in the next 3-5 years and add a mini split? AC unit in the current garage along with the RV Garage.

Based on what I'm seeing so far with my new house, I'm using about half the usage from my old house, but as stated, I want to leave some wiggle room from 2x mini splits and maybe a EV in the future.

I would like to be grid-tied and to sell back to the power company if need. I would also like to have the system stay on line if we lost power and the grid went down.

I have a budget of ~35K for everything.


Some questions regarding hardware:
I'm not sure what I need. I plan to have this on my roof and currently working with a company to do the design on my roof. They are building it off my blue prints of the home. So far, they are recommending 50 SolarEver 410w panels with IQ8+ micro inverters.

• Regarding the solar panels, how is SolarEver compared to Jinko? Do they both use micro inverters?
  • New/used, does it really matter? I'm looking at buying from SanTan Solar which is here in AZ.
    • New SolarEver 410w will run me about $250 each. X50 = $12,500
    • Used Jinko 400w will run me about $130 each X 52 = $6,760 (adding two more to cover the extra watts... this is just my basic math)
      • Can I use used solar panels in a grid tied system?
• I'm thinking about going with 2 Sol-Ark 15K systems as recommend by someone on Facebook, would this cover my needs?
  • Good? Bad? Cheaper options?
    • I'm not trying to go "cheapest" route as I want something that can grow if needed and as needed and not tied to one company. But don't want to spend extra money if not needed.
• Batteries - I got a recommandition of something like a 40 kwh system. Does this sound correct? How long would this last me? Looking back at my largest month in the last 3 years, I used 4,769 kwh for the month of Aug, 2020
• What else should I be researching regarding hardware? I just don't know what else I will need. I understand some wiring and a mounting system, that's simple enough. But what other parts to the solar system will I need for a grid tied, battery backed system?

Thank you so much for reading my novel. I'm just starting to research more and more of this and figured it would be best to have it all in one place as I come up with more questions, just easier to follow for me when it's all in one place.

Thanks again!

 

[Warpspeed]

I'm thinking about going with 2 Sol-Ark 15K systems as recommend by someone on Facebook, would this cover my needs?[/QUOTE}
Yes, but for 30,000kW you would need 2,000 of them.

Batteries - I got a recommendation of something like a 40 kwh system. Does this sound correct?

For 30,000 kW a 40kwh battery will last 40/30,000 of an hour or roughly .0133 hours or about 48 seconds.

 

[robby]

Something seems off with the size of the house and the consumption.
4769KWh in a month is some serious amount of power. That is 150+ KWh per day.
A 40KWh battery pack might give you 6 hours per night of power.
Yes you would need a sol-ark 15k but before buying two you need to confirm your monthly consumption.

 

[adamantium]

Based on your numbers...

14205 kWh / 264 days = 53.8 kWh/day
53.8 kWh/day * 365 days/year = 19640 kWh/year
53.8 kWh/day / 24 h/day = 2.24 kW

So your yearly consumption is about 20000 kWh per year and your current average load is about 2.25 kW.

Assuming you get on average around 8 hours of full sunlight a day every day of the year, you will need a solar array of 3 * 2.25 kW = 6.75 kW minimum to cover your current usage. Make that 8 kW just to be sure (20 panels).

An average mini split uses 600 watts/hour. Two of them will add 1.2 kW/h.

An EV requires huge power in the range of 50 - 100 kW per full charge (real world is around 75 kW maximum). Assuming the maximum and fully charging every day, you will require 100 kW in 8 hours of full sunlight. That's 12.5 kW per hour. So you would need 8 kW + 1.2 kW + 12.5 kW = 22 kW of solar power every day to run everything. The would require 55 x 400 watt panels or 54 x 410 panels.

Your number of panels is in the same ball park, but it seems like a large system. The EV would require more than half the system, and the size and complexity is high for a first time DIY system. Without the EV you would be down in the 10 kW range which still seems a little large for a 2500 square foot house. Do you plan to install 55 panels on your roof? Is there room?

You also need to work out the deal with micro, grid-tie, string, and hybrid inverters. Since you haven't provide information on how you plan to put it all together, I suspect that you don't know yet, and may not understand the purpose and differences between them. You need to decide how you are going to connect the PV system to the grid or the inverter. I think it might be good to consider a string inverter configuration unless you have shading or angle issues on your roof.

Batteries are rated in amp hours. So you need to convert your power needs from kWh to amp hours to determine how large of a system you will need and how much it will cost. Lead acid batteries typically range from 200 - 400 amp hours each @ 12VDC. Lithium (LiFePO4) typically range from 100 - 300 Ah @ 3.65VDC. Your inverter will probably require 48VDC. Assuming 12V lead acid batteries (50% discharge), to get near 40 kWh of usable power, you will need 2 x 4 x 200Ah x 4 = 32 deep cycle batteries. Lithium will require four times the number of cells, so a total of 128 cells. Both would provide 800 Ah @ 48VDC. That is a fairly large battery. It would run your house for a few hours. Although it is fairly large, you have to remember that the EV needs 50 - 80 kW per charge, so a 40 kWh battery won't be able to fully charge the EV every day. If you really are planning to charge an EV with the system, you will need to feed the grid all day long and then use the grid to charge the EV. You will still pay for electricity. If you use the battery, you won't be able to store enough to do a full charge, and you will wear the battery out.

Sol-Ark is probably the most expensive option out there. Maybe I would buy them if there price wasn't three times the alternative. You should look at alternatives unless you have plenty of money. Maybe consider scaling back the system for now.

Your month of August number comes out to an average load of 6.62 kW all day and night for 30 days straight. That is 3 times as high as your current rate of consumption. You must have had central air running non stop for a month in 115 degree temperature.

Before you buy anything you need to do your own calculations to make sure its all correct.

 

[Supervstech]

Grid tie solar is fun to calculate.
You need to produce in 5ish hours all of your daily consumption.
Your daily average on the old house was around 84kWh
So far, the daily on the new house is around 53kWh, but heavy ac season hasn’t been included yet…
You ask about a system able to handle 30,000kWh a year, which would be 82kWh a day… divided by 5 sun hours is… 16.6 kW of solar panels. With 82kWh of batteries.
That’s a tall order.

 

[Don B. Cilly]

80 kWh of batteries... some $15K (if you assemble them yourself).
16kW of panels... some $30K.
Inverters/SCCs to deal with all that... a lot ;·)
Cables, fuses, and sundries, quite a bit.

I would try and reduce consumption to some 10kWh/day - yes, ⅛ (I use 3), do yourself (and your country) a favour, and then think about solar ;·)
-

 

[A.Justice]

I just wanted to add that I would go with the used panels. Make the system larger than needed and grab a few extra to make up for any possible future failures. My system has 15 year old panels that I got for ~15¢ a watt, and they work perfectly.

Plus, direct use recycling is a good thing.

Also, I think it might be prudent to try to reduce your use before you design your system. Make sure you have energy efficient appliances, good insulation, and practice turning off devices when not in use. It seems petty, but it can make a HUGE difference.

 

[RV10flyer]

Plan for $60-80K if you DIY. As mentioned above, start with the highest efficiency equipment/appliances that you can afford. 20 SEER HVAC or higher and a HP water heater are top priority. They are the two largest consumers on our all-electric homes.

 

[Hedges]

Grid tie solar is fun to calculate.
You need to produce in 5ish hours all of your daily consumption.
Your daily average on the old house was around 84kWh
So far, the daily on the new house is around 53kWh, but heavy ac season hasn’t been included yet…
You ask about a system able to handle 30,000kWh a year, which would be 82kWh a day… divided by 5 sun hours is… 16.6 kW of solar panels. With 82kWh of batteries.
That’s a tall order.

82 kWh of batteries and 84 kWh daily consumption would mean ability to run about 24 hours without PV production.
Traditionally for off-grid, people looked for 3 days autonomy during heavy overcast, so 3x that size, 250 kWh
For grid-backup, consider just enough battery to make it through one night. 12 hours, 42 kWh?
But, is night time consumption same as daytime, or less?
If so hot you need A/C at night, might be. But even then, A/C shouldn't draw as much as when sun is beating down.

A backup generator would be a cheaper way to cover days with grid down and insufficient sun.

I live in a mild climate (San Jose) with poorly insulated house. I run A/C on hot days, with oversize PV system.
My battery has 14 kWh usable capacity, just enough for several inefficient old refrigerator/freezers, but only if I turn off excess yard lights and a tube amplifier. If I only had newer efficient refrigeration, smaller battery would work.

The goal for that approach is running major loads while the sun shines, shed all but the minimum when the sun goes down. Some systems will control relays based on SoC.

PV panels - fine to get quality panels used. I would avoid panels known to be peeling or otherwise degraded. Research brands, because only some hold up well. For a system with batteries and inverters able to start large motors, PV panels are a fraction of the total cost.

Grid tie PV equipment should cost $1/watt or so (a bit more now that RSD is required, or microinverters as an alternative.) Over 20 years, power amortizes out to $0.025/kWh. For off-grid, this can be AC coupled to battery inverter, if it supports frequency-watts.

For occasional grid failures, backup can be with lead-acid batteries. They can last 100 to 1500 deep cycles depending on type and cost, and will cost maybe $0.20 to $0.50/kWh of cycle life. That is what I have (AGM) due to price comparison two years ago.

Lithium batteries used to cost just as much, with higher price and longer life. Today "server rack batteries" may be $1600 for 5kWh and have claimed 6000 cycle life, could be $0.05/kWh over 16 years (if they actually last that long.)
In addition need battery inverters able to start and run loads like A/C.

 

[nscottsdale]

Careful with APS imposed max power size if you are going to be grid tied. I believe they go by your panel amp size. 200 amp service panel you can have a max of 15kw of solar (if you are grid tied). AND there is some other calculation where APS will look at real historical peak demand usage. For example we are frugal now but expect to be more liberal when we have solar - when exploring the grid tie APS they reduced our planned Tesla 15kw to 11kw max because we didn't historically use enough of the high priced power. We are installing non Tesla , non grid tie DIY now (in az and with solarever panels).

 

[Quattrohead]

I would size your system to cover the HVAC load and worry about something to charge an EV if you get one.
I don't see anything wrong with having more than 1 PV system doing individual tasks.
And on the EV side, do you have a full gas tank every morning and an empty tank every night in your petrol car ??? No, so you won't be filling your EV battery every night.

 

[robby]

Some questions regarding hardware:
Looking back at my largest month in the last 3 years, I used 4,769 kwh for the month of Aug, 2020

 

[tcj2001]

Correct me if I am wrong, If I have a 180kw consumption per day, i.e. 7.5kw per hour and If I have a solar panel of (3x7.5kwh) 22.5 kwh with 5.5 hrs. of sunshine I will generate 123kwh and will consume 41.25 kwh from the panel in 5.5hrs, I can send back 82.5kwh of excess to the grid which i can use back in the night. So I will only need a backup for remaining 7.5hrs x 7.5kwh = 56.25kwh battery storage for a 100% coverage.

 

[Danke]

Correct me if I am wrong, If I have a 180kw consumption per day, i.e. 7.5kw per hour and If I have a solar panel of (3x7.5kwh) 22.5 kwh with 5.5 hrs. of sunshine I will generate 123kwh and will consume 41.25 kwh from the panel in 5.5hrs, I can send back 82.5kwh of excess to the grid which i can use back in the night. So I will only need a backup for remaining 7.5hrs x 7.5kwh = 56.25kwh battery storage for a 100% coverage.

Depends on your power company’s Net Metering agreement.

For me it is not worth sending any back to grid, as they limit the size of solar system and only give $0.04/kWh that I’d send back.

 

[tcj2001]

Depends on your power company’s Net Metering agreement.

For me it is not worth sending any back to grid, as they limit the size of solar system and only give $0.04/kWh that I’d send back.

I live in Oklahoma currently they give dollar to dollar ratio. If I send 82.5 kw and I can use the entire 82.5 kw with in the year

 

[adamantium]

Yes. 180kwh - ( 22.5kw x 5.5h ) = 56.25kwh required per day. 82.5kwh back to the grid in 5.5 hours is 15kW per hour. So it is possible on a 100A service. You would need a 1500Ah battery capable of 80% depletion to do that every day. As mentioned above if you can't get back what you put in at 100% then you need even more to break even. Something is really wrong with the proposed consumption in this case. There is no way to put 50 400 watt panels on a 2500 sq ft house roof. There is no reason to need 180kwh of power every day unless you are charging two EVs a day and running AC all the time.

 

[robby]

There is no way to put 50 400 watt panels on a 2500 sq ft house roof. There is no reason to need 180kwh of power every day unless you are charging two EVs a day and running AC all the time.

Thanks! Everyone is running around doing the Math and I kept saying something is not right with his numbers.

 

[Shimmy]

Don't size for the future; your old house (based on construction year) was likely an energy hog. If/when you build the RV Garage consider adding more PV. I would size the battery at 2kWh/kW PV if you intend to remain grid-tied. Much more is unlikely to be economical. The RV Garage can integrate more later if you desire.

Buying used panels order 10% spares.

 

[SoloCon]

Something seems off with the size of the house and the consumption.
4769KWh in a month is some serious amount of power. That is 150+ KWh per day.
A 40KWh battery pack might give you 6 hours per night of power.
Yes you would need a sol-ark 15k but before buying two you need to confirm your monthly consumption.

He's a spreadsheet of monthly hours and total I was charged VS what I paid, along with how much power I used and when.
Hope this helps.

 

[robby]

He's a spreadsheet of monthly hours and total I was charged VS what I paid, along with how much power I used and when.
Hope this helps.

So what is the Goal?
Are you trying to just cut down the Bill and by how much?
The first thing I would do is go through the house and see what is consuming all of this power. I can see that it is happening in the Summer but a 2500Sq/ft house should not be using this kind of power. Is your Insulation good? Are the AC units fairly new and have the been cleaned?
Something is not adding up and you need to solve that first and then build the system based around a more energy efficient house.