ᐅ Annual Garden Water Demand – Is a Rainwater Harvesting System Worth It?
Created on: 18 May 2020 13:41
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Brainstorming
Hello everyone,
I am currently trying to estimate whether installing a rainwater cistern is worthwhile for our new build. We will have about 100 sqm (1,076 sq ft) of garden/lawn to plant. According to various online cistern calculators, I need roughly 8,000 to 11,000 liters (2,113 to 2,906 gallons) of water per year for this area in our region, which receives about 550 mm/sqm (22 inches/sq ft) of rainfall. The price for water and wastewater is approximately 2 euros per cubic meter. Based on this calculation, the cost for garden irrigation without a cistern would be around 22 euros per year.
If I now install a cistern with a capacity of 1,000 liters (264 gallons), I expect costs for the cistern, pump, and roof drainage connection to be between 1,000 and 1,500 euros. Assuming a budget of 1,000 euros, it would theoretically take more than 45 years for the cistern to pay for itself (without considering rising prices or repairs).
Am I missing something here? Could you possibly share your garden water consumption? Maybe the online calculators don’t match real-life usage.
Thanks
I am currently trying to estimate whether installing a rainwater cistern is worthwhile for our new build. We will have about 100 sqm (1,076 sq ft) of garden/lawn to plant. According to various online cistern calculators, I need roughly 8,000 to 11,000 liters (2,113 to 2,906 gallons) of water per year for this area in our region, which receives about 550 mm/sqm (22 inches/sq ft) of rainfall. The price for water and wastewater is approximately 2 euros per cubic meter. Based on this calculation, the cost for garden irrigation without a cistern would be around 22 euros per year.
If I now install a cistern with a capacity of 1,000 liters (264 gallons), I expect costs for the cistern, pump, and roof drainage connection to be between 1,000 and 1,500 euros. Assuming a budget of 1,000 euros, it would theoretically take more than 45 years for the cistern to pay for itself (without considering rising prices or repairs).
Am I missing something here? Could you possibly share your garden water consumption? Maybe the online calculators don’t match real-life usage.
Thanks
S
Stefan2.8418 May 2020 20:06Today we finished the excavation work for the cistern. I would have liked to have more capacity, but due to the very rocky soil, we could only make space for 7000 liters (1850 gallons). This is not for economic reasons. It’s more for peace of mind.
Vicky Pedia18 May 2020 20:29Stefan2.84 schrieb:
We finished the excavation work for the cistern today. I would have liked to have a larger one, but due to the very rocky soil, we could only make space for 7000 liters (about 1850 gallons). We’re not doing this for financial reasons—it’s more for peace of mind. A cistern is generally not cost-effective. I have a 10 m³ (about 2650 gallons) cistern myself and two 1 m³ (about 265 gallons) containers for my garden (approximately 70 m² / 750 sq ft), but only because I work in construction and got them for free. It’s a nice feature when it’s there, but I wouldn’t recommend building one purely from a financial standpoint.
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Brainstorming18 May 2020 20:42Fuchur schrieb:
Are you seriously talking about wastewater fees at €2.xx per m³ (cubic meter)? I have moved around Germany quite a bit, and wastewater fees have usually been around €4.xx, nowadays more like €5.xx.
Still, we won’t install a rainwater harvesting tank but a garden water meter instead, so we only pay for the freshwater.In our case, the sewer service charges for wastewater are €1.62 per m³ (cubic meter).
schubert7918 May 2020 20:44A cistern is not cost-effective.
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Stefan2.8418 May 2020 20:51No. It’s not cost-effective. But I think it’s a cool idea.
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