Off grid or self consumption

Weapons120 said:

How much battery backup do you currently have?

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I have 2 eg4s but I have net metering so the grid is like a big battery that is never full. When I get more batteries, I will get rid of net metering and tell the sol ark to keep the power in the home

Goboatingnow said:

I find 46 units a month for a Lived in home astonishing low.

In my case 1600 sq feet , the standby load is 2 units per 24 hours and 4 units per day actively being used , the vast amount of the extra 2 units is daily dishwater and washing machine. ( I run these on timers as I have night rate electricity 1/3 of the day cost. ) this doesn’t include water heating , in winter this is via oil fired central heating but we mostly burn firewood to heat the house. In summer there is extra usage due to night time water heating as the is no house heating running ( may through sept ). All my appliances are less then 5 years old.

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My wife and I use about 75 kw a month in the summer with both the ac units running...
I harvest 45 kw a month from 400 watts in the summer...


Don't know how anyone is using over 100 kw a month....

Check your meter??

jvin248 said:

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Do you have a water well pump? That may require a split phase 2x120v (240v), unless you installed a DC well motor more suitable for solar when you built the house. That sets up your inverter requirements, if you need water...

My current path, still assembling parts, is getting the off-grid inverter sorted out and having some panels with the goal of a 'gasoline generator replacement' for emergencies. I'll add batteries over time, add solar panels over time. I bought a good number of panels since they are the 'engine' for grid-down scenarios earlier this summer. Ordered a camper-style inverter+battery to be the quick emergency plug-in 'generator' for now. I'm in a construction permit necessary type of place so drawings, forms, approvals are the longest time issue. Otherwise I'd have posts in the ground and panels up already.

Do a ground mount as it's a lot more flexible than trying to hang off the house roof.

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I'm on a well...375 foot deep one...
We have 2500+ sq feet...
2 central air units...

Still don't make it over 100kw a month

Monkeychops said:

My wife and I use about 75 kw a month in the summer with both the ac units running...
I harvest 45 kw a month from 400 watts in the summer...


Don't know how anyone is using over 100 kw a month....

Check your meter??

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My house is all electric. 100kwh a month is impossible.

How many constant watts are we talking?
What are you wanting to off-grid?

I off-grid everything in my home that was important for security...
That draws just shy of 4 amps constantly....

I have 2 200 watt panels on my roof..can easily be removed for any repairs....

Check out my channel ....

Bkord said:

My house is all electric. 100kwh a month is impossible.View attachment 112381

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And that kiddos...REALLY SUCKS for him...

I’m not sure I understand when you say “units” of power. I have almost 6,000sqft of conditioned space with two heat pumps. My power bill averages around $120 a month. How does that compare with what you guys are seeing ?

Weapons120 said:

I’m not sure I understand when you say “units” of power. I have almost 6,000sqft of conditioned space with two heat pumps. My power bill averages around $120 a month. How does that compare with what you guys are seeing ?

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They mean kWh, I think, but some are so confused by misreading your original post it's hard to tell what they're saying.

I'd start small. That way you'll make $800 mistakes instead of $8000 ones. The first solar kWhs you produce each day are the cheapest, ones you store and use at night cost much, much more.

I'd reconsider net metering. It's usually a sweetheart deal for early adopters. And you'll probably get grandfathered in when more people sign up and they're forced to change to more realistic terms.

If you're dead-set against net metering, I'd recommend buying only enough panels for daytime loads at first. Let the grid fill in when clouds pass over, and at night. You'll over-generate at times, but it's OK to waste a little. Your mom won't scold you about power-starved children in Africa.

In time you might figure out ways to soak up that excess generation. If you have a well maybe pump water to a holding tank on a high spot. Maybe run the A/C before noon to pre-cool the house so you won't have to run it as much later when the sun gets low and panel output drops. Maybe get an EV on a smart charger programmed to only use excess generation. Lots of possibilities. Maybe even add a small battery to experiment, after you've grabbed the low hanging fruit.

If you want to kick self-consumption up to 90% or so you'll have to do more analysis and spend more money. Let's say 50 kWh/day average is your seasonal peak. And let's say 12 kW of panels at your location can supply 50 kWh/day on average in August. That might cost $8-10k (plus your free labor, ha). Now let's say 20 kWh of your daily consumption is after sunset. That's 25 kWh of LiFePO4 battery (80% DoD), so add 10k or so. Plus power electronics, cabling, etc.

These are just guesses, but ballpark. You need to study your actual consumption patterns and use the PV Watts calculator to estimate monthly panel output. That gives you a starting point, but does not address daily variation. So you'll still have days when you throw power away and others where you need the grid.

Design the system so you can easily expand it after you've spent a year or so gathering data. But in general going after that last 10% is very costly. At least you already have a generator, so you don't need a 100% solution.

Weapons120 said:

Hi,

Looking to build my own solar system. Have been reading and watching a lot of videos. I struggle with going to large and the price turns me off. I do not want to do net metering…I am interested in either off-grid or self consumption. Willing to listen to the positive/negative for both setups. Is it alright to post my last months power use ? Just looking for some guidance/confirmation.


View attachment 112131

Thanks,
Nathan

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That gives your daily Peak but do you know your peak draw?

Like mine last month peak draw was 12Kw peak draw.

If you want back up entire house that will determine how much inverter you need.

Total Peak amperage draw at one time over a month.

20 kw array should be fine.

I have about 3-4 days of batteries but you may opt for less. I have about the same draw as you daily. Maybe little more during summer.

Weapons120 said:

I guess I’m not following…my average is 50kw per day. I used 1,650 for the month of august. I posted a screenshot of my energy usage for the month of August above.

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Sorry for the confusion. My bad! I looked at 48kWh and I thought that was per month. Sorry I didn't realize it was 48kWh per day.

I"m assuming that is mostly for air-conditioning? I'd suggest you are likely to really need 5-6kWh of power just keeping the lights on and the refrigerator cold. So, what you really need is ~40+kWh of power just keeping the home cool?

Is this central air, or multiple point units? Do you know what the real-time amp draw on your unit(s) is/are? It might be appropriate to look at those 40+kWh as divided 2/3 during the day, an 1/3 at night. So let's say you need to supply ~12-15kWh of power overnight to keep the air-cons running. So, assuming you don't want to draw the battery bank down more than 50% (even for Li), then that means at least a 30kWh battery. 48V territory. For the daytime use, a good rule of thumb is to have 2X the number of panel watts as is your largest single load. So, an air-con requiring 3000W to run would need ~6000W of panels.

Assuming you have central air, that most likely means 240VAC. Most likely a single large split-phase inverter might not be big enough to carry that load, so you are likely to need at least two inverters in parallel to power it.

Self Consumption is the self reliant path if you are not 100% confident of net-metering continuing long term for you.

Our packs cost $.053/kwh before tax credit to cycle or .037 after tax credit, so if you save more than that by keeping your energy stored and using it at night vs. Selling it for cheap in daytime and buying for retail at night then you should turn an eventual profit on a battery bank plus get backup power at the same time.

Monkeychops said:

My wife and I use about 75 kw a month in the summer with both the ac units running...
I harvest 45 kw a month from 400 watts in the summer...


Don't know how anyone is using over 100 kw a month....

Check your meter??

Click to expand...

Monkeychops said:

My wife and I use about 75 kw a month in the summer with both the ac units running...
I harvest 45 kw a month from 400 watts in the summer...


Don't know how anyone is using over 100 kw a month....

Check your meter??

Click to expand...

Can you show us your power bill? And what model a/c are you using.

Monkeychops said:

Don't know how anyone is using over 100 kw a month....

Click to expand...

Any larger all electric home in a hot or cold climate can easily use that in a day. Homes which use gas or other fuels for heating and hot water often use much less electrical energy.

That said, the OP should be looking at ways to reduce consumption before going over the top on the supply side of the equation.

We are an all electric home in a warm to hot climate. Not a particularly good home thermally. We started out with an annual average of 52 kWh/day consumption.

We are now down to under 30 kWh/day. Much more to do to keep reducing our demand.



My more recent efforts have been at further reducing our grid imports:


That includes power for a second dwelling from start off 2020.

Have just started powering the home overnight via a grid assisted off-grid system. The small off-grid PV array charges the batteries which power the homes overnight. During the day the grid-tied PV system provides the power.

With the smart PV diverter for hot water and the off-grid system, I am working to get our average grid imports below 10 kWh/day. I can't eliminate it as I'm not building enough off-grid capacity to run our ducted aircon (heating and cooling) system, so it will require some grid power (at night mostly).

Bkord said:

My house is all electric. 100kwh a month is impossible.View attachment 112381

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You are using 900 kw hours in May and 700 kw hours in June
How are you reading the graph ?
I use about 35 kw hours a day about during summer and about 25 kw hours a day during spring and fall