The cost to heat a greenhouse in winter is usually $50 to $450 a month with electric heat. Your number depends on three things: size, wall material and how warm you keep it. A well-insulated greenhouse can cost half as much to heat as a single-pane one of the same size.
✅ Quick answer
- A small, insulated greenhouse kept frost-free costs about $50 to $250 a month, depending on your climate.
- Keeping it at 60°F instead of 45°F costs about 1.5 times more in a cold month.
- Single-pane glass loses about twice the heat of double-wall polycarbonate or insulated glass.
- Electricity averaged about 18.6¢ per kWh in the US in early 2026 (15¢ in Georgia). Check your own bill for your rate.
- Size your heater for your coldest night, not your average night. The formula is below.
We are a small, woman-owned greenhouse business in Georgia. Heating is one of the questions our customers ask us most. So we did the math for real greenhouses we sell, using real electricity prices. Here is what we found.
What decides the cost to heat a greenhouse?
A greenhouse loses heat through its walls and roof. The heater has to replace that heat, hour by hour. Four things set the bill:
- Surface area. Count the walls and roof, not just the floor. A taller house has more glazing to lose heat through.
- Glazing. Each material has a "U-value." That number shows how fast heat escapes. Lower is better.
- Temperature gap. The difference between inside and outside. Keeping 60°F on a 20°F night is a 40-degree gap.
- Energy price. Your rate per kilowatt-hour (kWh) or per gallon of propane.
How much heat does each glazing lose?
Greenhouse Management magazine gives these planning U-values. They already include normal air leaks.
| Glazing | U-value | Heat loss vs. single glass |
|---|---|---|
| Single-pane glass | 1.25 | 100% (baseline) |
| Double-wall polycarbonate | 0.7 | About 56% |
| Triple-wall polycarbonate | 0.6 | About 48% |
| Double-layer insulated glass | 0.7 or better | About 56% or less |
University of Arkansas extension data rates double-layer glass the same as double-wall polycarbonate. We used that number for insulated glass to stay on the safe side.
How many BTUs do I need to heat my greenhouse?
Greenhouse engineers use one simple formula. You only need three numbers, and a calculator.
📐 The greenhouse heat formula
BTU per hour = Surface area × U-value × Temperature gap
Surface area = walls + roof, in square feet · U-value = from the table above · Temperature gap = inside °F minus coldest outside °F
Step by step
- Find your surface area. Add up all the walls and the roof. Quick way: (perimeter × wall height) + (roof length × roof slope length × 2) + the two end gables.
- Pick your U-value from the table above.
- Find your temperature gap. Take the temperature you want inside, minus your typical coldest winter night. Your USDA zone is a good guide.
- Multiply the three numbers. The answer is the heat you need, in BTU per hour.
- Convert to watts for an electric heater: divide by 3.412.
- Add 20% as a safety margin.
🧮 Worked example: a Riga 4 on a 0°F night
- Surface area (walls + roof): about 390 sq ft
- U-value for twin-wall polycarbonate: 0.7
- Keep it 45°F inside when it is 0°F outside: gap of 45°F
390 × 0.7 × 45 = 12,285 BTU per hour. Divide by 3.412 = about 3,600 watts. Add 20% = about 4,300 watts. One 240V greenhouse heater covers it.
Want the monthly cost? Use your average winter night for the gap. Multiply the watts by the hours the heater runs, divide by 1,000 to get kWh, then multiply by your electric rate.
How much does it cost to heat a greenhouse per month? (Real numbers by size)
We used the formula above to estimate a cold winter month for five greenhouses. Here are our assumptions, so you can adjust for your own yard:
- Average winter night of 20°F (a typical cold month in much of the northern half of the US)
- The heater works 14 hours a night for 30 nights; the sun handles most daytime heat
- Electricity at 18.6¢ per kWh, the March 2026 US average from the EIA
- Surface areas are our own rough estimates from each model's dimensions
| Greenhouse | Floor space | Glazing | Kept at 45°F | Kept at 60°F |
|---|---|---|---|---|
| Typical 8x12 glass kit | 96 sq ft | Single-pane glass | ~$250/mo | ~$400/mo |
| Riga 4 (10x14) | 135 sq ft | 8mm twin-wall poly | ~$155/mo | ~$250/mo |
| Riga XL 6 (14x20) | 280 sq ft | 16mm triple-wall poly | ~$255/mo | ~$410/mo |
| Livingten 6 (12x17) | 195 sq ft | 22mm insulated glass | ~$270/mo | ~$430/mo |
| Same 12x17, single glass | 195 sq ft | Single-pane glass | ~$480/mo | ~$770/mo |
These are estimates for comparison, not a quote. Your real cost depends on your weather, your electric rate and how you run your greenhouse.
💡 What this table shows: the Riga XL 6 has nearly three times the floor space of a small glass kit, yet its heating bill is about the same. That is what good glazing buys you. The same 12x17 house in single-pane glass would cost about $200 to $340 more every month.
How does your climate change the number?
Here is the Riga 4 kept frost-free at 45°F in three climates, with the same assumptions as above.
| Winter climate | Avg. winter night | US avg. rate | Georgia rate |
|---|---|---|---|
| Mild (much of the South) | 35°F | ~$65/mo | ~$50/mo |
| Cold (Midwest, Mid-Atlantic) | 20°F | ~$155/mo | ~$125/mo |
| Very cold (northern states) | 5°F | ~$250/mo | ~$205/mo |
Your real bill will vary. Cloudy weeks push it up. Sunny days and a lower thermostat bring it down. Rates also vary by state, from about 12¢ in North Dakota to over 30¢ in parts of New England.
Which greenhouses are cheapest to heat?
For the size you get, double- and triple-wall polycarbonate and insulated glass win. Here are the three models from our table.
Hoklartherm Riga 2s to 5: the efficient all-rounder
The Riga 4 uses 8mm twin-wall polycarbonate on the main body and 10mm on the end walls. Its listing gives it 135 sq ft of floor space and a 15-year frame warranty.
The manufacturer is clear about why this matters. Greenhouses with thinner than 8mm twin-wall are "season extenders." They cost too much to heat through a real winter. See the full range and today's prices in our Riga greenhouse collection.
Riga XL 5 to 9: the most growing space per heating dollar
The Riga XL steps up to 16mm triple-wall polycarbonate. That is the lowest heat-loss glazing in our comparison. The Riga XL 6 offers 280 sq ft and four roof windows with automatic openers.
If you want to grow a lot through winter, this is where your heating dollar goes furthest. Our customers in snowy states often choose the XL for that reason.
Livingten: insulated glass for year-round living and growing
The Livingten is the choice when you want clear glass and low heat loss. It uses 22mm dual-pane glass (4mm glass, 14mm gas gap, 4mm glass). Its aluminum profiles are thermally insulated, which stops the frame from acting as a cold bridge.
It comes in three sizes: 163, 195 and 225 sq ft. Roof windows with solar-powered automatic openers, roll-up shade curtains and an LED light bar are included.
Our table likely overstates its heating cost a little, since we used a cautious U-value. Even so, it costs about half as much to heat as a single-pane house of the same size.
📌 About prices: greenhouse and heater prices change during the year, and we often run sales and manufacturer promotions. The price on each product page is always the current one. Any prices in this article are a guide from the time we wrote it (October 2026), not a quote or guarantee. Found a lower price for the same model at an authorized retailer? We offer a Price Match Guarantee - please check the rules first. Call us and we will confirm today's price and any current deals.
What size heater do I need for my greenhouse?
Monthly cost uses your average night. Heater size must cover your coldest night. Using the formula above on a 0°F night, here are our estimates:
| Greenhouse | Heat needed at 45°F | Heat needed at 60°F | Good heater match |
|---|---|---|---|
| Riga 4 | ~12,300 BTU/hr | ~16,400 BTU/hr | One 240V heater |
| Riga XL 6 | ~20,100 BTU/hr | ~26,800 BTU/hr | 240V heater plus backup |
| Livingten 6 | ~21,200 BTU/hr | ~28,200 BTU/hr | Two heaters |
Which heater fits which greenhouse?
We carry several electric heaters and one propane heater. All of them, with current prices, are in our greenhouse heater collection.
- Milkhouse heater: 120V, 1,300 or 1,500 watts, thermostat from 50 to 90°F. A good fit for small greenhouses up to about 150 sq ft in mild-winter areas, or as a backup heater.
- Bio Green Palma: 110V, 1,500 watts, splash-proof (IPX4). Also sold with the Thermo 2 digital thermostat. Best for small greenhouses in mild climates.
- Dr. Infrared DR-988: 5,600 watts at 240V, about 19,100 BTU at full power. Needs a dedicated 30-amp circuit. Made for large houses like the Riga XL.
- Riverstone Heating System: 2,500 to 5,000 watts at 240V, up to about 17,000 BTU. It mounts on the ceiling at 6 feet or higher, so it saves floor and bench space.
⚠️ Safety first: a 240V heater needs a dedicated circuit. Have a licensed electrician run it, and use a GFCI-protected outlet in a damp greenhouse. We always suggest a second, smaller heater as a backup. A failed heater on the coldest night of the year can wipe out a whole season.
Is electric, propane or passive heat cheaper?
Electric heat is clean and easy. It needs no venting, and a thermostat makes it precise. For most backyard greenhouses, it is the simplest choice.
Propane can cost less per BTU in some areas. Our RSI radiant propane heater puts out up to 18,000 BTU. It is a ventless heater, so it releases moisture and combustion gases into the greenhouse. Always give it fresh air as the manual directs, and use a carbon monoxide detector. Compare your local fuel price per BTU before you choose.
Passive heat costs nothing to run. Water barrels, stone and dark surfaces soak up sun by day and release it at night. It will not replace a heater in a cold climate, but it can trim your bill. Our guide to heating a greenhouse without electricity covers ten ways to do it. For a side-by-side look, read greenhouse heating options explained.
How can I lower my greenhouse heating bill?
Small changes make a big difference. These are the tips we share most with our customers:
- Turn the thermostat down. Many cool crops are happy at 40 to 45°F. Dropping from 60°F to 45°F cuts the bill by about a third or more.
- Seal the base. A tight foundation stops cold drafts. See our practical guide to a greenhouse foundation.
- Insulate the north wall. It gets little winter sun anyway. Foam board there cuts heat loss.
- Add thermal mass. Dark water barrels under benches store free solar heat.
- Use a fan for air circulation. It stops warm air from pooling at the roof, so the heater cycles less.
- Heat a smaller zone. Group tender plants on one bench and wrap that area.
- Use a thermostat with a remote alarm. You will know right away if the heater fails.
Is it worth buying a better-insulated greenhouse?
Usually, yes, if you plan to grow all winter. Better glazing costs more up front. But it saves money every cold month for as long as you own it.
💰 The savings add up: in our 12x17 example, insulated glass instead of single-pane saves roughly $200 to $340 a month in a cold winter. Over four cold months, that is about $800 to $1,300 a year, and you can buy a smaller heater too.
Insulated houses tend to be stronger too. Our list of the most durable greenhouses for wind, snow and harsh winters includes several of these models. Only need to guard against light frost? Then a single-pane glass greenhouse can still be a lovely choice.
Not sure which way to go? We answer every question personally. We also offer free shipping to the continental US and optional assembly crews.
Frequently asked questions
How much does it cost to heat a greenhouse in winter?
Most backyard greenhouses cost about $50 to $450 a month to heat with electricity. Small, insulated houses in mild areas sit at the low end. Large or single-pane houses kept warm in cold areas sit at the high end.
How do I calculate how many BTUs my greenhouse needs?
Multiply the surface area of the walls and roof by the U-value of your glazing, then by the temperature gap between inside and your coldest night. Add about 20% for safety. Our worked example above walks through it.
Is it expensive to heat a greenhouse in winter?
It can be if the glazing is thin. Single-pane glass or thin polycarbonate loses about twice the heat of double-wall or insulated glazing. Choosing good glazing is the biggest money saver.
What temperature should a greenhouse be in winter?
Keep it above 40 to 45°F for hardy greens and to overwinter most plants. Tomatoes, peppers and tropical plants want 55 to 60°F at night. Each degree warmer adds to your bill.
Can a 1,500-watt heater heat a greenhouse?
A 1,500-watt heater gives about 5,100 BTU per hour. That is enough for a small, insulated greenhouse in a mild climate. In colder areas or larger houses, you will need a 240V heater.
What is the cheapest way to heat a greenhouse?
The cheapest heat is the heat you don't lose. Start with good glazing and a sealed base, then add thermal mass. After that, an electric heater on a thermostat is usually the simplest and most reliable option.
Need help choosing?
Tell us where you live, what you want to grow and how warm you want it. We will help you match the right greenhouse and heater, and let you know about any current sales.