Connecting off grid homestead to the grid--am I crazy?

[hwy17]

I agree with your thinking. If you can get service at the shed affordably there are many options. You could even run a thinner 240v to a charger at the battery bank.

 

[zanydroid]

I used to say $1/W for grid tie PV hardware, but with PV panel deals I think I can do it for $0.50/W, bringing cost of power down to $0.01/kWh (amortized over 20 years.)

This is for roof mount or self-built (IE lots of sweat equity) ground mounts though, right?

I guess with no inspections the ground mounts get a little cheaper.

 

[zanydroid]

That being said, it looks like if I loosen my voltage drop requirements a bit, running a wire still seems like it would be feasible. For example, this 2 AWG wire is $1200/1000 feet, and should handle 30 Amps with only a 13 volt drop. And with the added bonus of possibly selling power back to the grid at some point, seems like it might be worth the investment. Plus, virtually zero maintenance costs.

This is 3-wire cable, which is good before your service equipment/first disconnect, but not after. Though 4-wire probably doesn't cost that much more since you can use a much smaller conductor for ground.

Also 3-wire is on the POCO side of the system, it's possible they have minimum AWG standards (IE I would guess either #1 or #2 aluminum would be their minimum, since that is the minimum size that can handle 100A minimum service size for a dwelling. #2 is allowed to carry 100A @ 75C due to the extra allowance when serving full dwelling load).

Pretty sure all the direct-bury cable worth burying is 600V rated. In which case you have the option of using 120/240 <-> 480V transformers.

Also I like the idea of smaller conductor serving 240V battery charger at the cabin going into a battery, which is then used to supply loads. The PowerPro is easily able to supply 10kW of power for EG cooking for 1 hour or whatever. And then slowly recover that over a few hours via either grid or solar. This trick is used for certain kinds of EV chargers like Freewire.

 

[Tomthumb62]

I honestly haven't done a ton of research, but these estimates seem like an order of magnitude lower than anything I've found. Do you have any suggestions on where to look to find affordable panels and batteries like this?

We could definitely make 20 kW work for us in the winter.

Since you’re basing your costs on what neighbors have told you, they might be basing it on prices from 5, 10 or 20 years ago. Solar is getting cheaper. But as @Hedges said, what does your utility charge per kilowatt hour?

 

[halfmoonhomestead]

It is ituitive if you think in terms of power. The explanation from a physics standpoint is that wire capacity is based on current not voltage. For the same power, if you increase voltage the current decreases. That is why kilovolt distribution and transmission lines are so thin, because they run and thousands of volts.

Right, I understand Ohms law and the inverse relation between current and voltage. Transmission uses high voltage at low amperage, way more efficient across long distances.

The unintuitive part of these voltage drop calculations is that the needed wire size decreases as voltage increases, with the same amperage. I.e., pushing 30 Amps at 120 Volts requires a larger wire to achieve a 5% drop than pushing 30 Amps at 240 Volts. This is because 5% of 240 is twice 5% of 120! So instead of a 6V drop, we're talking about an allowable 12V drop for 240... meaning the wire can be smaller.

 

[halfmoonhomestead]

This is 3-wire cable, which is good before your service equipment/first disconnect, but not after. Though 4-wire probably doesn't cost that much more since you can use a much smaller conductor for ground.

Provided I run the wire directly from the meter on the shed to the panel at the house, I think I can get away without a ground, right? It's no different than having the ground and neutral bonded at the main panel, a common practice.

Of course, then there will be no power at the shed, which is kind of ridiculous... I'll have to look into whether a ground wire is really "needed" in this case, or if it's just code

 

[halfmoonhomestead]

Also I like the idea of smaller conductor serving 240V battery charger at the cabin going into a battery, which is then used to supply loads. The PowerPro is easily able to supply 10kW of power for EG cooking for 1 hour or whatever. And then slowly recover that over a few hours via either grid or solar. This trick is used for certain kinds of EV chargers like Freewire.

Yeah, this is a really good point. It seems like even a small conductor connecting me to the grid could potentially solve all our problems.

Also, I'd like to note that we haven't even purchased this house yet... set to close any day now. This might all be moot once we see how much power the system really can put out, and how much we need. But being connected, if doable, just seems to make sense.

 

[hwy17]

Provided I run the wire directly from the meter on the shed to the panel at the house, I think I can get away without a ground, right? It's no different than having the ground and neutral bonded at the main panel, a common practice.

Yes this will work. I have an outbuilding that way. Downside is just some people might shake their head at you for it, but it's a free country (for you in no permit land, not the rest of us lol). You would then want a good ground rod at the house of course, like any normal main panel would have.

 

[zanydroid]

There might be some rules like how far the first OCPD can be from the meter and whether there needs to be a bond at that point.

I think at some point in the past you were allowed to run 3-wire to outbuildings and then form a new N-G bond at that point.

 

[ricardocello]

URD Cable (Direct Burial) | WireAndCableYourWay.com

URD is used for underground secondary distribution and service entrance applications at 600 volts or less. Shop duplex, triplex, quadruplex & single conductor.

www.wireandcableyourway.com

They have Quadruplex and Triplex depending if you want to run the separate ground or not.
The ampacities look favorable for smaller wire gauge, but 800 ft of voltage drop would be painful.
AWG Aluminum Wire Table

​

AWG	Diam. (mils)	Circular mils	Ohms/1000ft	Fusing Current	Pounds/1000ft
0000	460	212000	0.0804	-	195.0
000	410	168000	0.101	-	154.0
00	365	133000	0.128	-	122.0
0	324.85	105000	0.161	-	97.0
1	289	83700	0.203	-	76.9
2	258	66400	0.256	-	61.0
3	229	52600	0.323	-	48.4
4	204	41700	0.408	-	38.4

For #2 AWG, at 50A, voltage drop is 2 * 0.8 * 0.256 * 50 = 20.48 V (240V at the shed would be 219.5V at the house, 8.5% drop)
2 is both conductors, 0.8 is 800 ft/1000 ft, 0.256 is from the table, and 50 is amps.
Lower current would obviously have less voltage drop.
(Edited to use #2 because they don't sell #1).

They have {1/0 1/0 1/0 #2} Quadruplex, that would be
For 1/0 AWG, at 50A, voltage drop is 2 * 0.8 * 0.161 * 50 = 12.88 V (240V at the shed would be 227.1V at the house, 5.3% drop)
2 is both conductors, 0.8 is 800 ft/1000 ft, 0.161 is from the table, and 50 is amps.
$3.40 /ft. Qty 800 ft. $2,720.00

 

[CB350G]

I’m new at this, but here goes…

Aren’t most utility hook-ups 240v 1P? So run 100A service to the ’shed’ to a 100A box. (to keep the utility company happy). Then run whatever size wiring you see fit to the house. Run it as 240v, using appropriate breaker size. At your house, you can install a smaller breaker box, with normal 240 and 120 circuits. Never know when you might need 240 in the future.

On the flip side: Electric service will likely have a minimum monthly fee, regardless of usage. A small back-up generator might be cheaper, and definitely easier.

 

[zanydroid]

On the flip side: Electric service will likely have a minimum monthly fee, regardless of usage. A small back-up generator might be cheaper, and definitely easier.

How much is a weather-proof Generac and fuel tank that's big enough to buffer several days of bad winter production?

 

[CB350G]

How much is a weather-proof Generac and fuel tank that's big enough to buffer several days of bad winter production?

The only things that need to be ‘big enough’ are the battery bank and the fuel tank. From the OP, sounds like electrical loads are small.

If daily usage is 10 kWh /day, a small 3.5 kw inverter generator could recharge or top off the batteries each day.

Honda 3200 has a 2600w rated output and 3.3 hr run time on 1.2 gal. Allowing 80% eff, that’s 4.6 hrs of run time and less than 1.8 gallons. A 55 gallon drum would last a month. All theory, give or take.

No, not as cheap as utility juice, but if you’re just trying to get through a dark spell, it’s one option.

 

[zanydroid]

The only things that need to be ‘big enough’ are the battery bank and the fuel tank. From the OP, sounds like electrical loads are small.

If daily usage is 10 kWh /day, a small 3.5 kw inverter generator could recharge or top off the batteries each day.

Honda 3200 has a 2600w rated output and 3.3 hr run time on 1.2 gal. Allowing 80% eff, that’s 4.6 hrs of run time and less than 1.8 gallons. A 55 gallon drum would last a month. All theory, give or take.

No, not as cheap as utility juice, but if you’re just trying to get through a dark spell, it’s one option.

A wire from the utility has the user experience of a standby generator (weather proofing, automatic start wiring, convenient fuel plumbing, convenient auto-run to keep the juices lubricated). Honda 3200 is missing many of those.

If there is low production, it's a high probability that the weather is bad enough that you want a weatherproof generator.

 

[42OhmsPA]

Welcome to the forum @halfmoonhomestead .
My opinion, I would not want a grid line running to a location like that but I'm trying to find land so I can build without a grid line....

Have you done a power audit to determine your needs?
Have you looked at the pre packaged kits at Current Connected?

EG4 6000XP Inverter & SOK 48V Server Rack Battery Kit | Current Connected

Kit Includes: EG4 6000XP Off-Grid All-in-One Inverter/Charger SOK 48V 100Ah PRO Server Rack Battery (x3) 9" Pair of 1/0 AWG Pure Copper Battery Cables (x2) 7' Pair of 1/0 AWG Pure Copper Battery Cables Rich Solar 400W Solar Panels (x12) 100ft Raw PV Wire Solar Quick Connectors (x5)...

www.currentconnected.com

Also check out altE solar.

I'm in agreement with others, you can put together a diy kit at very affordable prices; saving even more if you build your own large battery bank.

 

[Checkthisout]

Rent an excavator, dig a trench and set the conduit for the power company so they can set a transformer close to your house.

This should greatly decrease cost.

Yes, get the grid connection. If you have to sell the money will have been better spent as well as ease of life.

You can then tinker with solar for backup and power savings.

 

[Madcodger]

Talk to your utility. Some are really good about providing free drops of xxxx feet with reasonable rates for various things. (others not so much) Some allow you to buy the conduit and bury it and they pull their wire in it. 800' will be high voltage with a pad mount transformer.

If you can get grid power for less than 10K certainly do that. That doesn't prevent you from spending another 5K-10K on solar and reducing your reliance on the grid.

I'd argue this is the best advice in this thread, and the only good place to start. If you are OK with potentially having grid power (some just don't want it, even with no install cost), then start by seeing what they're willing to do, at what cost. Everything else flows from there, with that information in hand. Don't rely on info from others. I've found "neighbor info" to be horribly unreliable. Most utilities will give you an estimate without cost. Start there.

 

[halfmoonhomestead]

I'd argue this is the best advice in this thread, and the only good place to start.

I'll be reaching out to the utility company soon asking for quotes for a new service at the road, and I can ask about other options.

Perhaps I don't fully understand, but I don't see how running conduit and having the utility company pull wire through it could possibly be cheaper than a $1200 triplex 2 AWG direct burial for a 30 amp service. I mean, the conduit alone must cost $1/foot at least. But, never hurts to ask I guess.

For reference, my parents were recently quoted $40,000 to run service 1200' down their driveway. They decided to go off grid with a real beefy system for about the same price.

 

[AZ Solar Junkie]

Do you have a stream with some flow and drop? Even seasonal?

Photovoltaic has become extremely economical. I think even with batteries you can do it for under $0.10/kWh. What does your utility charge?

A 2kW PV array can be had for $500, maybe $300 these days. In other words, 20kW of PV panels is affordable, biggest cost it mechanical mounts. How would 10x in production help your winter months?

Wow - how can you come up with a 2kW PV array for $500 let alone less? I'd love to find that kind of deal.

 

[zanydroid]

Wow - how can you come up with a 2kW PV array for $500 let alone less? I'd love to find that kind of deal.

For solar panels? Just look at any of the solar panels deals threads. $500 for just panels is easy. That number can’t possibly include inverter balance of system and racking though.