Is off grid (PV+Battery) better than grid-tie?

[lonestarcanuck]

Note - I live in Texas just north of Houston.

Currently, I have 1500 (5x315w) PV tied to a 1000W grid-tie inverter.

Goal to reduce my 60-100kWh (daily peek around 9100w) per day grid consumption by at least half and also have essential circuits on battery in case of Power outages.

I would like to do this in steps, maybe a 6000W inverter on one leg (120v) and eventually add a 2nd inverter (6000) on leg 2 (120v) for a combined L1/L2 = 240v at 12000w with 5 to 20kWh of battery (48v)

dilemma - we lose power at most we are down 2-10 hours per year - I live in the country. Ignore the winter a few years ago - that was once in 100 years.

Because of this dilemma, I am leaning towards a grid-tie and a possible UPS for essential circuits.

I am looking for some ideas or recommendations on maybe a Hybrid inverter that allows the best of both worlds or anyone else in similar situation and what you are doing?

 

[SeaGal]

I'm not familiar with US-based products, but sounds like a grid-tied hybrid will give you the flexibility that you are looking for. We have that here, also with typical outtages of 2h per year or so.

My only thought is that that, depending on whether those 10 hours are in one batch or more, you'll likely need more battery than 20kWh with the demand you use.

You didn't mention it, but assume you will be increasing the PV capacity to match the 12kW of inverters you are considering.

 

[Ampster]

It all depends on where you are standing. I am in California and my winter loads are greater than production so I need to use the grid as a seasonal battery. I am in a self consumption mode most of the time and at True Up have a small credit balance.

 

[lonestarcanuck]

I'm not familiar with US-based products, but sounds like a grid-tied hybrid will give you the flexibility that you are looking for. We have that here, also with typical outtages of 2h per year or so.

My only thought is that that, depending on whether those 10 hours are in one batch or more, you'll likely need more battery than 20kWh with the demand you use.

You didn't mention it, but assume you will be increasing the PV capacity to match the 12kW of inverters you are considering.

When I saw 10 hours per year, it usually means 15 minutes to maybe 2-3 hours. yes I will be adding 10-20 more
PV panels my goal is 8-12KW.

 

[lonestarcanuck]

It all depends on where you are standing. I am in California and my winter loads are greater than production so I need to use the grid as a seasonal battery. I am in a self consumption mode most of the time and at True Up have a small credit balance.

I believe I am standing in "Texas"
my demand in the winter falls a lot

8/29/2022​	3133​
9/27/2022​	2407​
10/27/2022​	1710​
11/28/2022​	1475​
12/28/2022​	1637​
1/26/2023​	1405​
2/27/2023​	1575​
3/29/2023​	1390​
4/28/2023​	1472​
5/30/2023​	1687​
6/27/2023​	2672​
7/27/2023​	3326​

This is my last 12 months of consumption - June/2023 was 2670kWh for the month vs under 1500kWh for winter months.

 

[Hedges]

If grid-tie net metering is available (1:1 credit for backfeed), that is most cost effective.
Even if backfeed is only credited 1/2 or 1/4 of what you pay to buy power, depending on how cheaply you install PV, it can be more cost effective than batteries.

Many states are doing away with net metering, pushing people toward batteries.
Zero-export and using power when you produce it (e.g. variable speed water pumping) may be an alternative.

If you have time of use rates, price when you produce and when you consume can change that equation.

Backup with PV & batteries is nice when grid is down. It comes at a cost. The less backup you need, the cheaper it is.

Batteries are expensive, but 48V batteries are the most economical. Some inverters use more proprietary high voltage batteries, and those cost more.

SolArk is popular, and can build high wattage split-phase or 3-phase systems.

I use SMA Sunny Island and Sunny Boy, which work well but may not be available with features required for new grid-tie installs. Will see what new models do later.

 

[lonestarcanuck]

If grid-tie net metering is available (1:1 credit for backfeed), that is most cost effective.
Even if backfeed is only credited 1/2 or 1/4 of what you pay to buy power, depending on how cheaply you install PV, it can be more cost effective than batteries.

Many states are doing away with net metering, pushing people toward batteries.
Zero-export and using power when you produce it (e.g. variable speed water pumping) may be an alternative.

If you have time of use rates, price when you produce and when you consume can change that equation.

Backup with PV & batteries is nice when grid is down. It comes at a cost. The less backup you need, the cheaper it is.

Batteries are expensive, but 48V batteries are the most economical. Some inverters use more proprietary high voltage batteries, and those cost more.

SolArk is popular, and can build high wattage split-phase or 3-phase systems.

I use SMA Sunny Island and Sunny Boy, which work well but may not be available with features required for new grid-tie installs. Will see what new models do later.

I don't really care if the utility gives me money, I just want to get m bill down to as close to zero as I can our rate is constant and my rural rate is 09.3 cents. our summer bills are $300-$400 and winter $150-$220 range. we are cooling 3400SF and 1000SF shop as well. its been over 100F for the last 6 weeks so bill is running closer to $400 ATM

so I am thinking two 6000W hybrid inverters or maybe just 6000W off grid and put 8 circuits it with grid as a fall back so (PV/Batter priority and Grid 2nd)

 

[Hedges]

It's not being given money, rather being given credit on your bill.

If PV creates 1kW continuously, and your A/C draws 2kW but is on 15 minutes, off 15 minutes, you still buy half the power (assuming zero export PV). With net metering, the meter spins back and forth, nets out to zero. (used to be mechanical and spinning, today is electronic.)

GT PV hardware costs me $1.00 or so per peak watt of production. Typical sunshine hours, works out to $0.025 or $0.03/kWh amortized over 20 years.

Turnkey installed maybe $2 to $4/W, works out to break even with your $0.09/kWh utility bill so you save nothing.

Batteries may cost as little as $0.05/kWh by the time they wear out (some forum members, optimistic about cycle life, come up with $0.025/kWh.) Other batteries may be $0.10/kWh, some cost $0.50/kWh.

So I favor more PV, less battery if possible. Given that my system is grid-backup, not full-time offgrid. I have a small battery good for only one night.

Considering purchase price, installation labor, and anticipated lifetime, see what it will cost you to make and maybe store your own power.

 

[lonestarcanuck]

It's not being given money, rather being given credit on your bill.

If PV creates 1kW continuously, and your A/C draws 2kW but is on 15 minutes, off 15 minutes, you still buy half the power (assuming zero export PV). With net metering, the meter spins back and forth, nets out to zero. (used to be mechanical and spinning, today is electronic.)

GT PV hardware costs me $1.00 or so per peak watt of production. Typical sunshine hours, works out to $0.025 or $0.03/kWh amortized over 20 years.

Turnkey installed maybe $2 to $4/W, works out to break even with your $0.09/kWh utility bill so you save nothing.

Batteries may cost as little as $0.05/kWh by the time they wear out (some forum members, optimistic about cycle life, come up with $0.025/kWh.) Other batteries may be $0.10/kWh, some cost $0.50/kWh.

So I favor more PV, less battery if possible. Given that my system is grid-backup, not full-time offgrid. I have a small battery good for only one night.

Considering purchase price, installation labor, and anticipated lifetime, see what it will cost you to make and maybe store your own power.

I know my meter is the new electronic with the arrows going both directions and cycles through the usage and pushed back, I guess need to talk to the utility about making sure I am getting credit, although with 1.5KW I am not really sure I am impacting my bill al lot by only producing about 9-10kWh with my current setup.

I am an electrical engineer and live in the country/Texas and will do most of the work myself. not a fan of turnkey.

 

[timselectric]

"Is off grid (PV+Battery) better than grid-tie?"

There's no right or wrong answer. It's just personal preference.

That said,
off grid is the only way to go.

 

[SamDeleted]

Is it better ? YES

Is it more expensive, also yes ...

 

[1201]

are you already grid tied with PTO from POCO? IF so dont waste your time with batteries.

the reasons people go off grid are:
1. there is no grid
2. they want "freedom" from the government who is watching their energy use.
3. we dont want to deal with jumping through hoops to get PTO

 

[Texican]

I live in NE Texas, The net metering in Texas is not real good.
The first 10 years I gave away for free all my excess kwh from my grid tie 11kw system
because I still had a lot of grid usage and the deals they offer for solar buyback charge a big premium over a regular plan, so it was overall cheaper to give the excess for free

18 months ago ,we added an off grid 12kw system with 30kwh batteries, now being mostly off grid it was cheaper to get the best buyback deal available here.
thats about 4 cents kwh equal to what you send them, and then 18 cents per kwh above what you send them

a lot of your load must be 240v (hvac) so 1 inverter at 120v may not help much
12 kw of panels and at least 20 kwh batteries would cut your usage 8 months out of the year almost completely
covering the hot summer here is harder
I have 23kw of panels total, my july bill was 34 dollars, but august I estimate about 125

 

[Hedges]

I know my meter is the new electronic with the arrows going both directions and cycles through the usage and pushed back, I guess need to talk to the utility about making sure I am getting credit, although with 1.5KW I am not really sure I am impacting my bill al lot by only producing about 9-10kWh with my current setup.

I am an electrical engineer and live in the country/Texas and will do most of the work myself. not a fan of turnkey.

Find out what the terms are, and if you can increase system size.
There is inverter size, and then there is array size which they don't really need to know about if you expand. Multiple orientations, and you can boost output 40% above what a single orientation could deliver.

We've had changes to plans, and expanding could land us on a new schedule.

Yea, I do virtually 100% of everything myself, so it takes a while.

Plan out what you may want for the future, and put in equipment that supports it.
You might add a smaller grid-interactive backup system, separate from existing. Or, you might AC couple to existing.

If using lithium batteries, best to have communications between BMS and inverter, although some people here make systems that don't talk. If I go lithium, I expect to use REC BMS for compatibility with my Sunny Island.

 

[wattmatters]

Goal to reduce my 60-100kWh (daily peek around 9100w) per day grid consumption by at least half

I know you are asking about the energy supply side (solar PV and battery, on/off grid), but what about the energy demand side of the equation?

Do you have options to reduce your energy demand? What is consuming all that energy?

We had pretty high energy demand as well with our first full year averaging 52.2 kWh/day, (high of 66kWh/day for the Summer quarter, low of 40 kWh/day for Autumn qtr) and aside from adding both grid-tied PV and eventually also off-grid PV + battery, we also took steps to reduce our energy consumption.

We've managed to reduce our home's annual average consumption by 20 kWh/day. I'm still working on that, more to do.

This makes the job of self energy supply and bill reduction much easier and cheaper as you need less PV and battery plus of course less energy imported from the grid.

Below shows our quarterly average daily energy consumption split by the source of energy supplying it (grid vs our own production) over the past nearly eight years:



This includes the additional second occupied dwelling added at start of 2020.

Our annual average grid imports are down by 45 kWh/day.

 

[wildbillpdx]

I'm in the process of setting up an off-grid AIO with batteries. We already have a New, grid-tied 9.2kWh system we just installed since we had to re-roof. We had an old (17yrs) PV grid-tied system and had a bunch of 200watt panels after we replaced our system. Purchased an EG4 6000ex and three EG4 LifePower4 batteries (48v) to use partially as backup and partially to help offset more of our monthly power bill. The Sanyo panels are mounted on the ground for the AIO. Going to use existing manual transfer switch to make the connection to some of our circuits, which has been powered by a gas generator for year, and will still be around for additional backup.

 

[Shimmy]

For cutting your bill in half, you need about 10kW of PV, and depending on how your time of use/nighttime loads goes likely about 10-15kWh of battery storage to absorb the excess solar.

If that is a good match, the EG4-18kWPV inverter and single PowerPack (14kWh) from Signature Solar would give you a nice clean install.

 

[SamDeleted]

2. they want "freedom" from the government who is watching their energy use.

It's more about independence than freedom from spying eyes

 

[1201]

It's more about independence than freedom from spying eyes

For you sure, but I'm on several off grid solar forums and invisibility from the spying government is one of the common motivators I've seen.

Hey there are people out there who honestly KNOW the earth is flat, and only 6000 years old ?

 

[SamDeleted]

For you sure, but I'm on several off grid solar firms and invisibility from the spying government is one of the common motivators I've seen.

Hey there are people out there who honestly KNOW the earth is flat, and only 6000 years old ?

Yea there's crazy people everywhere..
like all you loony evolutionists and round earthers ?