Your Ideal Offgrid New Construction Setup

• Location: North Georgia Mountains
• Family size: 5; 2 adults and 3 kids
• Lot size: 10 acres, sloping lot
• Home size/type: ~4k square ft / modern mountain design
• We have one EV and use it the most, but also have a gas-powered vehicle
• Electricity from the utility company is an option, but it would cost $30k just to run the line to our house. Hence my push to go completely off-grid (among other reasons),

• Solar array + battery system to cover most, if not all of our energy needs
• Build a ground-based solar rack system (as opposed to adding panels to our roof)
• Propane-powered generator for when the sun doesn't shine enough
• Heat pumps to heat/cool house
• A hot tub (I know, not great to have on a solar system, but we'd be willing to not use it during low energy periods, if that helps!)

• Heat pumps
  • Do we use an air-to-air or air-to-water system?
  • Do we go with dual fuel, or stick with electric and use the propane generator to charge the batteries to power the heat pumps when solar is insufficient?
• Hot water
  • Do we go with a standard hot water tank (KISS), and focus more on the solar + battery side of things, or do we do something a little more creative like:
    • heat pump hot water tank
    • using the water side of an air-to-water heat pump to help heat the water we use
    • use a solar water heating system on our roof
  • Do we go with a tankless system?
• Solar Panels
  • How many do you think we need?
• Batteries
  • Given the fact that we will likely need two heat pumps, do we need a high surge type battery like the Power Wall 3?
  • What total capacity do you think we need?

Hedges said:

I doubt electric heat from PV in winter is practical. Check an insolation calculator.
A/C from PV should be great.

Heat with wood, oil, propane?

How much will this project cost?
Is paying $30k for power connection unreasonable? Will utility reduce that on account of adjacent properties which could eventually be developed?

Propane generation of electric may cost $1/kWh, but run the numbers. I've heard that for diesel.
CHP, combined heat and power, could be attractive. Use waste heat from exhaust and water cooling system to heat house, while also generating electricity.


Some people use low-priced import inverters. Keeping a spare, wired or on the shelf, is affordable and a good idea. Don't know their lifespan yet.

There are also tier-1 brands including Schneider, Outback, Midnight, SMA, Victron, and others. Those can still fail, but 20 year lifespan is reasonable to expect.

PV is 20% efficient. Solar hot water may be 60% efficient. PV to resistance or heat-pump water heater is likely the way to go, given price and reliability of PV. And same panels can serve other purposes, like powering the A/C.

Have backups for everything.

Water supply? Well?
Some pumps are the largest load you'd have to deal with. Grundfos offers zero surge inverter drive pumps.

Instant water heater? zero benefit.
A storage water heater is another energy storage method, cheaper and more reliable than batteries.

LiFePO4 is the way to go for off-grid. It needs to be kept above freezing to charge, and not to hot.
Best if it is not in the house, to eliminate fire risk. Which is low but non-zero for that chemistry. Earth-sheltered?

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mecdatlanta said:

...
If you were us, what would you do? We're just trying to figure out the major pieces before we reach out to vendors. If you would change any (or all of) what we think we want, please say so. My wife will kill me if she has to sweat it out in the hot GA summers!

Don

Click to expand...

mecdatlanta said:

Greetings All,

This site is amazing and I am learning a ton. But I feel like I know enough to get my family into some potentially hot - or worse yet - cold (due to insufficient energy planning!) water.

Here is our situation, as best I can describe it. Nothing is carved in stone, although we do have the house plan, the lot, and the need to start building in the next few weeks/months so our kids can be in school next Fall (2025), so I need to figure out the energy side of things pretty quickly:

• Location: North Georgia Mountains
• Family size: 5; 2 adults and 3 kids
• Lot size: 10 acres, sloping lot

Click to expand...

mecdatlanta said:

• Home size/type: ~4k square ft / modern mountain design

Click to expand...

mecdatlanta said:

• We have one EV and use it the most, but also have a gas-powered vehicle

Click to expand...

mecdatlanta said:

• Electricity from the utility company is an option, but it would cost $30k just to run the line to our house. Hence my push to go completely off-grid (among other reasons),

Click to expand...

mecdatlanta said:

What we think we want:

• Solar array + battery system to cover most, if not all of our energy needs

Click to expand...

mecdatlanta said:

• Hot water
  • Do we go with a standard hot water tank (KISS), and focus more on the solar + battery side of things, or do we do something a little more creative like:
    • heat pump hot water tank
    • using the water side of an air-to-water heat pump to help heat the water we use
    • use a solar water heating system on our roof

Click to expand...

mecdatlanta said:

• Do we go with a tankless system?

Click to expand...

mecdatlanta said:

Greetings All,

This site is amazing and I am learning a ton. But I feel like I know enough to get my family into some potentially hot - or worse yet - cold (due to insufficient energy planning!) water.

Here is our situation, as best I can describe it. Nothing is carved in stone, although we do have the house plan, the lot, and the need to start building in the next few weeks/months so our kids can be in school next Fall (2025), so I need to figure out the energy side of things pretty quickly:

• Location: North Georgia Mountains
• Family size: 5; 2 adults and 3 kids
• Lot size: 10 acres, sloping lot
• Home size/type: ~4k square ft / modern mountain design
• We have one EV and use it the most, but also have a gas-powered vehicle
• Electricity from the utility company is an option, but it would cost $30k just to run the line to our house. Hence my push to go completely off-grid (among other reasons),

What we think we want:

• Solar array + battery system to cover most, if not all of our energy needs
• Build a ground-based solar rack system (as opposed to adding panels to our roof)
• Propane-powered generator for when the sun doesn't shine enough
• Heat pumps to heat/cool house
• A hot tub (I know, not great to have on a solar system, but we'd be willing to not use it during low energy periods, if that helps!)

What we don't know enough about:

• Heat pumps
  • Do we use an air-to-air or air-to-water system?
  • Do we go with dual fuel, or stick with electric and use the propane generator to charge the batteries to power the heat pumps when solar is insufficient?
• Hot water
  • Do we go with a standard hot water tank (KISS), and focus more on the solar + battery side of things, or do we do something a little more creative like:
    • heat pump hot water tank
    • using the water side of an air-to-water heat pump to help heat the water we use
    • use a solar water heating system on our roof
  • Do we go with a tankless system?
• Solar Panels
  • How many do you think we need?
• Batteries
  • Given the fact that we will likely need two heat pumps, do we need a high surge type battery like the Power Wall 3?
  • What total capacity do you think we need?

If you were us, what would you do? We're just trying to figure out the major pieces before we reach out to vendors. If you would change any (or all of) what we think we want, please say so. My wife will kill me if she has to sweat it out in the hot GA summers!

Don

Click to expand...

mecdatlanta said:

Greetings All,

This site is amazing and I am learning a ton. But I feel like I know enough to get my family into some potentially hot - or worse yet - cold (due to insufficient energy planning!) water.

Here is our situation, as best I can describe it. Nothing is carved in stone, although we do have the house plan, the lot, and the need to start building in the next few weeks/months so our kids can be in school next Fall (2025), so I need to figure out the energy side of things pretty quickly:

• Location: North Georgia Mountains
• Family size: 5; 2 adults and 3 kids
• Lot size: 10 acres, sloping lot
• Home size/type: ~4k square ft / modern mountain design
• We have one EV and use it the most, but also have a gas-powered vehicle
• Electricity from the utility company is an option, but it would cost $30k just to run the line to our house. Hence my push to go completely off-grid (among other reasons),

What we think we want:

• Solar array + battery system to cover most, if not all of our energy needs
• Build a ground-based solar rack system (as opposed to adding panels to our roof)
• Propane-powered generator for when the sun doesn't shine enough
• Heat pumps to heat/cool house
• A hot tub (I know, not great to have on a solar system, but we'd be willing to not use it during low energy periods, if that helps!)

What we don't know enough about:

• Heat pumps
  • Do we use an air-to-air or air-to-water system?
  • Do we go with dual fuel, or stick with electric and use the propane generator to charge the batteries to power the heat pumps when solar is insufficient?
• Hot water
  • Do we go with a standard hot water tank (KISS), and focus more on the solar + battery side of things, or do we do something a little more creative like:
    • heat pump hot water tank
    • using the water side of an air-to-water heat pump to help heat the water we use
    • use a solar water heating system on our roof
  • Do we go with a tankless system?
• Solar Panels
  • How many do you think we need?
• Batteries
  • Given the fact that we will likely need two heat pumps, do we need a high surge type battery like the Power Wall 3?
  • What total capacity do you think we need?

If you were us, what would you do? We're just trying to figure out the major pieces before we reach out to vendors. If you would change any (or all of) what we think we want, please say so. My wife will kill me if she has to sweat it out in the hot GA summers!

Don

Click to expand...

Bluedog225 said:

Propane for now seems wise.

Click to expand...

mecdatlanta said:

Heat pumps

• Do we use an air-to-air or air-to-water system?
• Do we go with dual fuel, or stick with electric and use the propane generator to charge the batteries to power the heat pumps when solar is insufficient?

Click to expand...

mecdatlanta said:

heat pump hot water tank

Click to expand...

mecdatlanta said:

Solar Panels How many do you think we need?

Click to expand...

mecdatlanta said:

Batteries What total capacity do you think we need?

Click to expand...

Bluedog225 said:

Whatever you do, keep in mind two things.

1. DIY is going to be a lot cheaper than purchase. But it will take time.

2. Don’t buy a single thing until you have a complete plan. The folks here can look at it for you.

Price a system based on your energy needs (watts per day and peak demand). Look at currentconnected.com and some cheaper places. And look at vendor reputations in this forum.

Propane for now seems wise.

Click to expand...

• cargo container - 30ft insulated- delivered to the lot
  • Have a concrete pad ready for it.
  • frame with steel studs
  • insulate the heck out of it - I know it is insulated but unless you pay for one for a freezer it isn't enough
  • Add a divider around 8ft from one end - totally
  • Add man sized fireproof doors at both ends.
  • The divider should be flame proof - as in steel studs, and firerock on both sides of the wall, rockwool inside
  • 8 x 3" pass-through - 4 on each side of the container - get caps for the ones that won't be used right off
  • figure you will use 2 of them to start - but it is way simpler to add them to start and low cost than figure out you are missing one.
  • Ventilation ducts at top and bottom that fall closed with loss of power - large ones
• Wall space will be a premium - decide early in the design on all-in-one or separate components and a vendor
• I picked UL listed Victron for my stuff - so---
  • MPPTs along the common wall
  • Inverters on the left wall - you would probably need 6 or 8 from your pie in the sky
  • AC components on the opposite wall with a cable tray above
  • Work out every detail before buying a thing
• In the opposite end of the container
  • Alcoves along one side with fireproof doors - 3
    • Walls lined with firerock and insulated with rockwool.
    • each alcove contains
      • Duct from the inverter part of the container
      • Temperature sensors - top/middle/bottom - RPi controller
      • LED light - bright one
      • Duct to the outside in case the temp rises indicating a fault/vent battery
      • Fire suppressant??
      • glass window to the outside - dual pane from oven glass (view port) - small 2"
      • One or more batteries
        • first one off the shelf batteries - 6 pack or so
        • The others - DIY batteries - 3 or 4 each
    • pass-through to a bus bar outside the room
    • The outside bus bar is connected via contactor to LARGE cables to the inverter part of the container
• Service entrance type setup from the inverter output - use AL SER wire to the house a ways away

robbob2112 said:

So, here are some WAGs I've thought about when I was in your shoes - having researched a LOT - and this is just for the container to house it in.

YES, it is pie in the sky what I would do with endless funds - a simpler version would do the job I am sure. Your power requirements are pretty large - I would bet 400amp service if you went with the grid - insulate and prevent heat/cool loss as much as you can, save a ton by avoiding energy need at all where possible.

The others can guess at sizing - but I can say that geothermal heat pumps last longer and are more efficient that the air-air units. But for the price of having someone install it for you, you can afford a tiny backhoe used for $5k and do it yourself and come out money ahead. Especially when you factor in all the other uses there will be around the place.


Make sure your house exterior is as fireproof as you can get it - wildland urban interface windows inflammable exterior, deck/porch materials that won't burn. Better yet your recreation area away from the house a bit so anything directly outside the house can be sacrificed to fire without endangering the house itself.


I spitball this container at $12k to 15$ fitted out - this is just to house the $40k investment in gear and there will be another $20k in panels or more.

Start with the container and the minimum you think you need and you can add more equipment over time

• cargo container - 30ft insulated- delivered to the lot
  • Have a concrete pad ready for it.
  • frame with steel studs
  • insulate the heck out of it - I know it is insulated but unless you pay for one for a freezer it isn't enough
  • Add a divider around 8ft from one end - totally
  • Add man sized fireproof doors at both ends.
  • The divider should be flame proof - as in steel studs, and firerock on both sides of the wall, rockwool inside
  • 8 x 3" pass-through - 4 on each side of the container - get caps for the ones that won't be used right off
  • figure you will use 2 of them to start - but it is way simpler to add them to start and low cost than figure out you are missing one.
  • Ventilation ducts at top and bottom that fall closed with loss of power - large ones
• Wall space will be a premium - decide early in the design on all-in-one or separate components and a vendor
• I picked UL listed Victron for my stuff - so---
  • MPPTs along the common wall
  • Inverters on the left wall - you would probably need 6 or 8 from your pie in the sky
  • AC components on the opposite wall with a cable tray above
  • Work out every detail before buying a thing
• In the opposite end of the container
  • Alcoves along one side with fireproof doors - 3
    • Walls lined with firerock and insulated with rockwool.
    • each alcove contains
      • Duct from the inverter part of the container
      • Temperature sensors - top/middle/bottom - RPi controller
      • LED light - bright one
      • Duct to the outside in case the temp rises indicating a fault/vent battery
      • Fire suppressant??
      • glass window to the outside - dual pane from oven glass (view port) - small 2"
      • One or more batteries
        • first one off the shelf batteries - 6 pack or so
        • The others - DIY batteries - 3 or 4 each
    • pass-through to a bus bar outside the room
    • The outside bus bar is connected via contactor to LARGE cables to the inverter part of the container
• Service entrance type setup from the inverter output - use AL SER wire to the house a ways away

Stucco the outside of the container and put fans and a mini-split inside the inverter room and battery area.

The point of all this is to have a power room separate from the house in case there is a fire and separation between sections inside in case there is a fault at any one of them. Climate control by using waste heat as much as possible and if that isn't enough a mini-split and fans to exhaust heat and/or cool when that isn't enough

The stucco on the outside is to protect the power cargo container


And, note - we decided not to move for a few years so my pie will be stale and rotten when it is time to eat it

Click to expand...

mecdatlanta said:

• Heat pumps to heat/cool house
• A hot tub (I know, not great to have on a solar system, but we'd be willing to not use it during low energy periods, if that helps!)

What we don't know enough about:

• Heat pumps
  • Do we use an air-to-air or air-to-water system?
  • Do we go with dual fuel, or stick with electric and use the propane generator to charge the batteries to power the heat pumps when solar is insufficient?
• Hot water
  • Do we go with a standard hot water tank (KISS), and focus more on the solar + battery side of things, or do we do something a little more creative like:
    • heat pump hot water tank
    • using the water side of an air-to-water heat pump to help heat the water we use
    • use a solar water heating system on our roof
  • Do we go with a tankless system?

Click to expand...