Greenhouse Water Storage Calculator
See how many days your rain barrels or water tanks will keep your greenhouse watered between rains, and how much storage you need.
Please note: these results are estimates
This calculator gives general estimates based on typical conditions and the information you enter. How long your water lasts depends on the weather, the type and size of your plants, your watering method, evaporation, local rainfall and how full your tanks start. Your actual results may be different, so use these numbers as a starting point for planning, not a guarantee. Always follow the manufacturer's instructions, and talk to a qualified professional before making important decisions. Questions? Call us at 678-408-8222.
How it works
How long will my rain barrels last?
A greenhouse in summer uses roughly 0.1 gallons of water per square foot of floor each day, a little more for big, thirsty plants and in hot, dry weather, and about half that in spring and fall. Drip irrigation wastes less, so the same water goes about 30% further.
Days = Water stored (gal) ÷ (Floor (sq ft) × Daily use per sq ft × Crop × Watering method)
We also show how much rain refills your storage, using the same greenhouse roof: about 0.5 gallons per square foot for every inch of rain, after losses. For the full picture, try our Rainwater Calculator.
Planning a more self-reliant garden? Read our guide to going off the grid with a greenhouse.
Questions
Water storage FAQ
How much water does a greenhouse use per day?
About 0.1 gallons per square foot of floor on a summer day. A 10 x 12 ft greenhouse uses about 12 gallons a day in summer, and around half that in spring and fall.
How many rain barrels do I need for a greenhouse?
Enough for two weeks without rain is a good goal. For a 10 x 12 ft greenhouse in summer, that is about 170 gallons, or three 58-gallon barrels.
How can I make my stored water last longer?
Use drip irrigation, water in the early morning, and mulch the beds. Linking two tanks together, or adding a larger tank, gives you more of a buffer between rains.
Can I link rain barrels together?
Yes. A tank connection kit joins two barrels or tanks at the bottom, so they fill and drain together like one larger tank.
More tools
Other greenhouse calculators
- Heater Size CalculatorHow many BTUs it takes to keep your greenhouse warm on the coldest night.
- Heating Cost CalculatorWhat a winter of heating will cost with electric, propane or natural gas.
- Fan and Ventilation CalculatorThe exhaust fan CFM and vent openings that keep summer heat down.
- Snow Load CalculatorHow much the snow on your roof weighs and when to brush it off.
- Foundation CalculatorConcrete, gravel, pavers and lumber for your greenhouse base.
- Greenhouse Size CalculatorHow big a greenhouse you need for the plants you want to grow.
- Shade Cloth CalculatorThe right shade percentage and cloth size for your greenhouse.
- Grow Light CalculatorHow many grow lights it takes to give your plants enough light in winter.
- Rainwater CalculatorHow much rain your greenhouse roof can catch, and how many barrels you need.
Want a second opinion?
Tell us about your greenhouse and where you live, and we will help you get it right.
Call 678-408-8222Send us a message