Going Off the Grid with a Greenhouse

Even the Pentagon is planning for 90 days off the grid. Here's a simple, four-step plan for making your family more self-sufficient with a greenhouse: pick an efficient one, catch your own rainwater, use a little solar power, and grow more fresh food in a small space.

โœ… Quick answer

  • A greenhouse will not replace an emergency kit. It adds fresh food, saved water and more peace of mind.
  • Step 1, greenhouse: the walls decide how much heat you keep. Twin-wall polycarbonate loses roughly 40% less heat than single glass, and 16 mm triple-wall about 60% less.
  • Step 2, water: every inch of rain on 1 sq ft of roof gives about 0.623 gallons. A 10 x 12 ft greenhouse can catch about 60 gallons from a 1 inch rain, after losses. Our Graf rain barrels hold 45 to 345 gallons.
  • Step 3, power: solar fans and heat-powered vent openers keep a greenhouse cool with no grid power. Electric heat on solar is rarely practical.
  • Step 4, food: grow up with shelves, grow more in raised beds, plant in small batches and extend the season with cold frames.
  • Our free greenhouse calculators help you size each part.
  1. Step 1๐Ÿก Greenhouse
  2. Step 2๐ŸŒง๏ธ Water
  3. Step 3โ˜€๏ธ Power
  4. Step 4๐Ÿฅฌ Food

In the news

Why is everyone talking about going off the grid?

Two preparedness stories made headlines in October 2026. Neither one is a reason to worry. But they are a good reminder that a little self-reliance at home is a smart, calm thing to plan for.

The Pentagon's "FORTRESS" plan

On October 25 and 26, 2026, Fox News and then Fortune reported on a Pentagon plan called FORTRESS. It is developing a requirement for major US military bases to keep operating for at least 90 days without the civilian power grid.

The UK's "Be Ready" campaign

On October 22, 2026, the UK launched its "Be Ready" campaign. It asks households to be ready for 3 days of disruption, with 3 litres of water per person per day.

What the US asks of families

Ready.gov says households should be ready to "survive on your own for several days," with 1 gallon of water per person per day.

Sources: Fortune, October 26, 2026 and Ready.gov: Build a Kit.

๐Ÿ“Œ Important: the 90-day goal is for military bases, not for families. No government is asking households to store 90 days of food or water. For your home, follow the Ready.gov guidance above.

Be realistic

What does off-grid mean for a backyard grower?

For most of our customers, "off the grid" does not mean leaving town. It means being a little less dependent on the store, the water bill and the power line. A greenhouse is a great tool for that.

  • It grows fresh food close to your kitchen, for more months of the year.
  • It can catch its own water from the roof, in barrels you control.
  • It can run its fans on the sun and open its vents with no power at all.
  • It builds skills, like seed starting, composting and saving water, that you keep for life.

What a greenhouse does not do is replace a full emergency kit. You still need stored drinking water, food, a first aid kit, medicines, a flashlight and a radio. Ready.gov has a good checklist on its Build a Kit page. Think of your greenhouse as one more layer of resilience, not the whole plan.

Want the bigger picture? Our article From Food Security to Self-Sufficiency: Why Families Are Turning to Greenhouses covers why so many families are growing their own.

Step 1 ยท Greenhouse

How do you choose an energy-efficient greenhouse?

Everything else in this guide depends on the greenhouse itself. An efficient greenhouse holds its heat on cold nights, stays cooler on hot days and needs less help from the power line. Here is what to look for.

  • ๐Ÿงฑ1. Insulated walls and roofThe glazing is the biggest factor. Thicker, multi-wall panels trap air and hold heat much longer. See the table below.
  • ๐Ÿงญ2. Face it to the sunRun the long side east to west so it faces south, and pick a spot with at least 6 hours of winter sun.
  • ๐Ÿ“3. The right sizeSize it for what you grow (about 4 sq ft per tomato plant). More air volume also means steadier temperatures.
  • ๐ŸŒฌ๏ธ4. Enough ventsAim for roof vents equal to about 15โ€“20% of the floor area. Automatic openers work them for you, with no power.
  • ๐Ÿ—๏ธ5. A tight base and doorsA level, sealed foundation and well-fitted doors stop cold drafts. A strong frame handles wind and snow.
  • ๐Ÿ’ง6. Room for rain catchingGutters and a downspout turn the roof into a free water supply. Ask us which models include gutters.

Glazing at a glance: which walls hold heat best?

R-value measures how well a material holds heat. Higher is better. These are typical values, and each brand's numbers vary a little.

Glazing Approx. R-value Light Best for
Single-pane glass about R-0.9 Very clear, about 90% Spring to fall growing, mild winters like Georgia's, and classic good looks
8โ€“10 mm twin-wall polycarbonate about R-1.6 to 1.7 Soft, diffused, about 80% Year-round growing in most of the US, at a lower price
16 mm triple-wall polycarbonate about R-2.4 to 2.5 Diffused, about 70โ€“75% Cold winters and the lowest heating bills
22 mm dual-pane insulated glass about R-2 or better Clear Four-season growing with the look of glass

๐Ÿ’ก What the numbers mean: heat loss through the walls goes down as R-value goes up. Moving from single glass (R-0.9) to twin-wall (R-1.6) cuts that heat loss by roughly 40%. Triple-wall (R-2.4) cuts it by about 60%. That means a smaller heater, less fuel and more growing days when the power is out.

Greenhouses to consider

Here are a few of our customers' favorites, from a budget starter to a fully insulated four-season greenhouse.

  • Riverstone MONT 8x12 polycarbonate greenhouse in black
    Best value starter

    Riverstone MONT 8' x 12'

    From $4,149.99

    A sturdy polycarbonate greenhouse in sizes from 8' x 8' up to 8' x 24'. It pairs with the made-in-USA MONT solar fan kit.

    See the MONT โ†’
  • Hoklartherm Riga 3s arch greenhouse with twin-wall polycarbonate
    Year-round, small yard

    Hoklartherm Riga 3s 8' x 11'

    From $5,499

    A German arch greenhouse with twin-wall polycarbonate, built for growing in every season. The Riga family runs from 8' x 7' to 14' x 30'.

    See the Riga 3s โ†’
  • Hoklartherm Riga 4 arch greenhouse
    Best seller

    Hoklartherm Riga 4 10' x 14'

    From $8,099

    Room for a real food garden, with 8 mm twin-wall on the main body and 10 mm on the front and back walls.

    See the Riga 4 โ†’
  • Hoklartherm Nelke 4 Pro greenhouse with 16 mm triple-wall polycarbonate
    Extra insulation

    Hoklartherm Nelke 4 Pro 10' x 14'

    From $11,499

    Thick 16 mm triple-wall polycarbonate, our pick for cold-winter areas and the lowest heating bills in its size.

    See the Nelke 4 Pro โ†’
  • Janssens Royal Victorian VI23 8x10 glass greenhouse in a garden
    Classic glass

    Janssens Royal Victorian VI23 8' x 10'

    From $9,799

    Crystal-clear glass and an aluminum frame from Belgium. Bright, beautiful and ideal for spring-to-fall growing and mild winters.

    See the VI23 โ†’
  • Livingten insulated glass greenhouse
    Most insulated glass

    Livingten 22 mm Insulated Glass

    From $48,000

    22 mm dual-pane glass and thermally insulated aluminum frames, in 12' x 15', 12' x 17' and 12' x 20'. A true four-season garden room.

    See the Livingten โ†’

๐Ÿ’ฒ About prices: prices shown were checked in November 2026 and can change at any time, up or down, as manufacturer prices and promotions change. Please check the product page for today's price.

Found a lower price from an authorized dealer? See our Price Match Guarantee and its rules.

Not sure which one fits your yard? Try the greenhouse size calculator, read our Livingten insulated greenhouse review, or browse the full Riga collection. A good base matters too, so see our practical guide to a greenhouse foundation.

Step 2 ยท Water

How can a greenhouse collect its own water?

A greenhouse roof is a ready-made rain catcher. Add gutters, a downspout and a rain barrel, and you have soft, chlorine-free water right where your plants need it.

Gallons โ‰ˆ Roof sq ft ร— Inches of rain ร— 0.623

Some water splashes, evaporates or overflows. Our rainwater calculator multiplies by 0.8 to allow for that, which works out to about half a gallon per square foot for every inch of rain. This is an estimate, and your real numbers will vary.

Example: a 10' x 12' greenhouse has 120 sq ft of roof. A 1 inch rain gives 120 ร— 1 ร— 0.623 = about 75 gallons. After losses (ร— 0.8), you can plan on about 60 gallons.

Graf Top Tank 345 gallon rain water tank in a garden
The Graf Top Tank stores 345 gallons and comes with a brass tap and a downspout connection kit.

What size rain barrel does your greenhouse need?

Size your barrel to hold the water from one good 1 inch storm. Here is a quick guide, using the footprint of the greenhouse as the roof area.

Greenhouse size Roof area Water from a 1" rain* Barrels that fit
8' x 8' 64 sq ft about 32 gallons Madera, VASO or Linus (58 gal)
8' x 12' 96 sq ft about 48 gallons Arondo (66 gal) or Terranova (73 gal)
10' x 14' 140 sq ft about 70 gallons Venetia (80 gal) or Stone 2-in-1 (93 gal)
10' x 20' 200 sq ft about 100 gallons Quadro Slim (132 gal) or Venetia (133 gal)
14' x 23' 322 sq ft about 160 gallons Antique Amphora (158 gal) or CUBUS (264 gal)
Bigger, or a house roof 500+ sq ft 250+ gallons Top Tank (345 gal), or link two tanks with a connection kit

*After about 20% losses. Use the rainwater calculator for your exact roof and local rainfall.

Our Graf rain barrels and water tanks

Made in Germany by Graf, these closed barrels keep out mosquitoes, leaves and sunlight, and they are built from UV-stable plastic that won't rot, chip or crack like wood or clay. Many are in stock now in limited quantities.

  • Graf Quadro Slim rain water tank
    Tight corners

    Graf Quadro Slim

    45 or 132 gal ยท from $299.99

    A slim square tank with a small footprint. The tap fits in any of 3 outlet positions.

    See the Quadro Slim โ†’
  • Graf Venetia Amphora terracotta-look rain barrel on a patio
    3 sizes

    Graf Venetia Amphora

    63, 80 or 133 gal ยท from $359.99

    A graceful terracotta-look urn in tough HD-PE plastic, sized for a patio or a big vegetable garden.

    See the Venetia โ†’
  • Graf Madera wood-look rain barrel
    Wood look

    Graf Madera

    58 gal ยท $459.99

    Looks like a wooden cask but never rots. Removable cover with a child lock, so you can dip a watering can right in.

    See the Madera โ†’
  • Graf Terranova oval stone-look rain barrel
    Narrow spaces

    Graf Terranova Oval

    73 gal ยท $459.99

    Only 16" deep, with a stone-like texture. It tucks against a wall right where the downspout comes down.

    See the Terranova โ†’
  • Graf VASO 2-in-1 rain water tank with planter
    Tank + planter

    Graf VASO 2-in-1

    58 gal ยท $469.99

    A tall grey vase with an 8" deep plant cup on top. Water below, flowers or herbs above.

    See the VASO โ†’
  • Graf Arondo stone-look rain water tank
    Stone look

    Graf Arondo

    66 gal ยท $499.99

    A compact round tank with a lifelike stone finish and a childproof removable cover.

    See the Arondo โ†’
  • Graf Linus 2-in-1 rain water tank with planter
    5-year warranty

    Graf Linus 2-in-1

    58 gal ยท $619.99

    Graf's premium compact tank, with a textured surface, a plant cup on top and brass threads.

    See the Linus โ†’
  • Graf Top Tank 345 gallon rain water tank
    Biggest storage

    Graf Top Tank

    345 gal ยท $699.99

    Commercial-grade, yet only 66 lbs empty. Comes with a brass tap and a downspout connection kit.

    See the Top Tank โ†’
  • Graf CUBUS garden rain water tank
    Most per dollar

    Graf CUBUS Garden

    264 gal ยท $769.99

    264 gallons in a square 32" x 32" footprint, which uses space better than a round tank.

    See the CUBUS โ†’
  • Graf Stone 2-in-1 rain water tank with plant cup
    Silver or Lava

    Graf Stone 2-in-1

    93 gal ยท $999.99

    A smooth stone column with a plant cup on top and brass threads for the tap.

    See the Stone โ†’
  • Graf Antique Amphora rain barrel with planter, 158 gallons
    Showpiece

    Graf Antique Amphora

    158 gal ยท $1,299

    An aged-terracotta amphora with handles and a planter on top. The piece your neighbors ask about.

    See the Antique Amphora โ†’

The add-ons that make it work

See them all in our rain barrels and water tanks collection.

๐Ÿ’ก Free heat from water: every gallon of water stores about 8.3 BTU for each ยฐF it warms up. A 55 gallon dark drum of water inside your greenhouse that warms 20ยฐF on a sunny day gives back about 9,000 BTU overnight. Rainwater is a free way to fill it.

โ„๏ธ Plan for winter: Graf says to leave the tap open when it freezes. Before a hard frost, drain the barrel with a water removal kit so it can't crack.

๐Ÿ“Œ Important: stored rainwater is for your plants, not for drinking. Keep your drinking water separate and follow Ready.gov. Rainwater rules also vary by state, so please check your state and local rules before you set up barrels.

For the full guide, see how much water plants need in a greenhouse.

Step 3 ยท Power

Can you run a greenhouse without grid power?

Yes, for the most important job: keeping plants from overheating. Fans, vents and controls use little power, so the sun can run them. Heat is a different story, and we cover that below.

Solar fans

Our solar powered greenhouse supplies include two complete solar fan kits:

MONT solar powered ventilation system for a greenhouse
The MONT solar ventilation system runs its fan on solar power.

Vent openers that need no power at all

Automatic window openers use a tube of paraffin oil that expands as the air warms. The Janssens automatic roof window opener and the Riga automatic window opener start opening at around 72ยฐF and push the window open up to about 14". When it cools, a spring pulls the window shut. No wiring and no battery.

The RSI 18" louver window also opens and closes on its own with a temperature-sensitive opener arm.

๐Ÿ’ก Tip: size your fan with our fan calculator, then size the panel and battery with our solar panel calculator. Our guide to a solar-powered greenhouse setup walks through it step by step.

Why is electric heat on solar impractical?

A heater uses far more power than a fan. Our solar calculator page works out that a 1,500 W heater running 8 hours a night uses 12,000 Wh. In a Georgia December, that takes about 4,600 W of panels plus a very large battery bank. For most people, that costs more than the greenhouse.

The better plan is to keep heat in with an insulated greenhouse (Step 1) and water for thermal mass (Step 2), then use propane or grid power for the heater when you need it. Size it with our heater calculator and see the options in our greenhouse heater collection. Our guides on heating a greenhouse without electricity and cooling a greenhouse without electricity have more low-power ideas.

Step 4 ยท Food

How do you grow more food in a small greenhouse?

You do not need a huge greenhouse to grow a lot. You need to use every layer of space and keep it full all year. Here are the four best ways, with the tools that make each one easy.

๐Ÿชด Grow up with shelves and seed trays

Use the space above your beds. Shelves hold seed trays, herbs and pots, and they free the floor for tall crops like tomatoes and cucumbers on strings or trellises.

  • Janssens shelves and seed trays inside a Royal Victorian greenhouse
    For Janssens

    Janssens Shelves or Seed Trays

    From $280

    Made to fit Royal Victorian greenhouses. Choose shelves for pots or trays for seedlings.

    See it โ†’
  • Shelves for Riga greenhouses
    For Riga

    Shelves for Riga Greenhouses

    From $319

    Neat, sturdy shelving made for the Riga arch greenhouses.

    See it โ†’
  • MONT greenhouse shelves and workbench
    For MONT

    MONT Shelves & Workbenches

    From $399.99

    A work station kit designed for the 8 ft MONT greenhouses, with room to pot up and grow.

    See it โ†’
  • Riga heavy duty seed trays
    Seed starting

    Riga Heavy Duty Seed Trays

    From $60

    Strong trays that sit on Riga shelves, for starting seeds by the dozen.

    See it โ†’

๐Ÿฅ• Grow more in raised beds

Raised beds give you deep, loose soil that warms early and drains well, and they are easier on your back. Use them inside the greenhouse or right outside it.

  • Ergo Quadro stacking raised beds
    Stack to any height

    Ergo Quadro Stacking Raised Beds

    From $95

    Square beds you stack as high as you like, so you can garden standing up.

    See it โ†’
  • Eden deep root V-shaped garden table
    Deep roots

    Eden Deep Root V-Shaped Garden Table

    From $210.95

    A raised table with a deep V for tomatoes, peppers and carrots, at a comfortable height.

    See it โ†’
  • Juwel Kombi raised bed and cold frame
    2-in-1

    Juwel Kombi Raised Bed & Cold Frame

    From $219.99

    A raised bed with a cover, so it works as a cold frame in spring and fall.

    See it โ†’

โ„๏ธ Stretch the season with cold frames

A cold frame is a mini greenhouse for the ground. Start seedlings weeks early and keep salad greens growing into winter, right outside your greenhouse door.

  • Juwel year-round 4x2 cold frame
    Year-round

    Juwel Year-Round 4' x 2' Cold Frame

    From $229

    Dual-layer 4 mm polycarbonate cover, plus insect netting for summer.

    See it โ†’
  • Juwel BioStar 1500 cold frame 5x3
    Most room

    Juwel BioStar 1500 Cold Frame 5' x 3'

    From $524

    A roomy premium cold frame with a no-drip design, for lots of early plants.

    See it โ†’

๐Ÿ‚ Feed the soil with compost

A composter turns kitchen and garden scraps into rich, free food for your beds. It closes the loop, so you buy less soil and fertilizer.

  • Eco Master compost bin in two sizes
    Simple start

    Eco Master Composter

    From $110

    A classic Graf compost bin in two sizes, easy to set up in a corner of the yard.

    See it โ†’
  • Mr. Spin dual compartment compost tumbler
    Turn and done

    Mr. Spin Dual Compost Tumbler

    From $199

    A 43 gallon tumbler with two compartments: one cooking, one filling.

    See it โ†’
  • Aerobin 400 insulated composter
    No turning

    Aerobin 400 Composter

    From $549

    Insulated, with a built-in aeration core, so it composts without turning.

    See it โ†’

๐ŸŒฑ Plant in small batches: sow a short row of lettuce or radishes every couple of weeks, so you harvest a little all the time instead of all at once. This is called succession planting, and it keeps a small greenhouse producing all year.

๐Ÿ’ก Tip: use the greenhouse size calculator to see how much space your plants need. It allows about 4 sq ft per tomato plant. Then check the grow light calculator to see if winter crops need extra light.

๐Ÿ’ฒ About prices: prices were checked in November 2026 and can change at any time. Please check each product page for today's price, and see our Price Match Guarantee rules.

Browse all of our greenhouse shelves, garden beds, cold frames and composters. For more ideas, read how to maximize space in a greenhouse and our month-by-month planting guide.

Plan it

Your off-grid greenhouse checklist

  • โ˜€๏ธPick a sunny spotAt least 6 hours of winter sun, good drainage and a short walk from the kitchen.
  • ๐Ÿ Choose an efficient greenhouseSize it for your crops. Twin-wall, triple-wall or insulated glass if you want to grow through winter.
  • ๐ŸŒง๏ธCatch the rainGutters, a downspout kit and a closed rain barrel sized for one good 1 inch storm.
  • ๐ŸŒฌ๏ธVentilate without the gridHeat-powered vent openers plus a solar fan with a thermostat.
  • ๐Ÿ”ฅHold heat in winterInsulate, add water as thermal mass and keep a propane or grid heater as backup.
  • ๐ŸชดGrow up and grow moreShelves, raised beds, trellises and small, frequent sowings.
  • ๐Ÿ‚Close the loopCompost scraps and use the compost to feed your beds.
  • ๐ŸงฐKeep a real emergency kitStored drinking water, food and supplies, following Ready.gov.
  • ๐Ÿ“žAsk usCall 678-408-8222 and we will help you plan your setup.

Free tools

Free calculators

Questions

Off-grid greenhouse FAQ

Is the government telling families to store 90 days of supplies?

No. The 90-day figure comes from a Pentagon plan for major military bases to run without the civilian grid. For households, Ready.gov says to be ready to survive on your own for several days, with 1 gallon of water per person per day. The UK's Be Ready campaign asks households to be ready for 3 days.

Can a greenhouse make my family self-sufficient?

It can make you more self-sufficient, with fresh food, rainwater for plants and less need for grid power. It does not replace an emergency kit with stored drinking water, food and supplies.

What is the most energy-efficient type of greenhouse?

One with insulated glazing, a south-facing position and a sealed base. Twin-wall polycarbonate (about R-1.6) loses roughly 40% less heat than single glass (about R-0.9), and 16 mm triple-wall (about R-2.4) about 60% less. Insulated dual-pane glass, like the Livingten, gives the look of glass with much better heat retention.

How much rainwater can a greenhouse roof collect?

About 0.623 gallons per square foot of roof for every inch of rain, or about 0.5 gallons after losses. A 10 x 12 ft greenhouse can collect about 60 gallons from a 1 inch rain. These are estimates.

What size rain barrel do I need for my greenhouse?

Pick a barrel that holds the water from one 1 inch rain: about half a gallon per square foot of greenhouse footprint. An 8 x 8 ft greenhouse needs about 32 gallons, a 10 x 14 ft about 70 gallons and a 10 x 20 ft about 100 gallons. For more storage, link two tanks with a connection kit.

Can solar panels run a greenhouse?

Solar works well for fans, vent controls, sensors and small pumps. Electric heat on solar is rarely practical, because a heater uses far more power than a fan. Use insulation, non-electric vent openers and a propane or grid heater as backup.

Do automatic vent openers need electricity?

No. Wax or paraffin-oil openers expand as the air warms and push the window open. A spring closes it again when it cools.

What is the best way to grow more food in a small greenhouse?

Grow up with shelves and trellises, use raised beds, sow small batches every couple of weeks, and extend the season with cold frames and good insulation.

Ready to plan your off-grid greenhouse?

๐Ÿ… BBB Accredited ยท A+ Rating๐Ÿšš Free Shipping, Continental US๐Ÿ’ฒ Price Match Guarantee

We are a small, woman-owned, family-run greenhouse business in Atlanta, Georgia, and we answer every call ourselves. Tell us your yard, your climate and what you want to grow, and we will help you plan your greenhouse, water, power and growing space.

Call us Monday to Friday, 9 AM to 6 PM, or Saturday, 10 AM to 3 PM (Eastern). Live chat and email are open almost around the clock.

Call 678-408-8222 [email protected]