Saving money with rainwater 💦 harvesting from your commercial building


  • ✔️Step 1: Find the historic rainfall levels in your area from Met Eireann:
    Met Eireann Monthly Data
  • ✔️Step 2: Calculate your building’s roof collection area from Google Maps:
    Google Maps Right Click in map, select measure distance, draw a line around the roof and it will calculate the Roof Area in m²
  • ✔️Step 3: Calculate your potential Annual rainwater yield:
    Annual rainwater yield = P x A x R
    P = annual rainfall in mm
    A = Roof collection area in m2
    R = Roof Co-efficient

Let’s look at an example:

Site Location : Dublin 15
Roof Area : 10,028m²
Roof Co-efficient : 0.8**
Rainfall : 757.9 mm/ Mean avg. / Year
Weather Station : Dublin Airport Station
Potential Water Savings : 757.9 x 10,028 x 0.8 = 6,080,177 Lt/Year
Area Potential Rainwater Water Savings: 6,080,560.45 Litres/Year or 6,080m3 /Year
Financial Savings : 6,080m3 x €1.99* = €12,099 / Year!
*Dublin Water Charges: Supply m3: €1.16, Wastewater Services m3: €0.83, Combined m3: €1.99
**typically you should expect to collect 80% of this rainwater each year due to losses in filtering and small rainfalls that do not generate enough runoff

If you need any further information or help, do not hesitate to contact us