How much rainwater can I harvest?

HOW MUCH WATER CAN I HARVEST?

The amount of rainwater you can harvest depends on the size of your roof, on how many downspouts you connect to, and how large a system you have.

So grab your calculator, find the square footage of your roof and let’s work it out.

Calculate your homes rainwater harvest potential.

If it rains 1 inch in one day, a 1000 sq. ft. roof will yield 623 gals of water per day.

Home Rainwater harvest formula.

Number of gallons of rain fall harvested = 1 inch of rain x 0.623 x your roofs square footage


Example:
The average home can harvest 1246gal = 1” x 0.623 x 2000sqf

 

Calculating your rainwater harvest per year.


So to get a relatively accurate forecast of your homes rainwater harvest potential. Check the rainfall for your closest city. For instance the province of Ontario on average has only 19” of rain per year. While the city of Toronto gets an average of 50” of rain a year.

A Homes yearly rainwater harvest formula

Number of gallons of rain fall harvestable per year = inches of rain per year x 0.623 x your roofs square footage

 

Example: The average home in Toronto can harvest 63,546 gal of rain per year = 51” x 0.623 x 2000sqf

How much is your rainwater worth?

To calculate the value of your homes rainwater harvest. Find the cost of water per gallon from your local municipality and multiply it by your yearly rainwater harvest. The 2019 municipal Rates for water in Toronto, Ontario is $0.01797927/gal

A homes yearly rainwater value formula. 


Number of gallons of rain fall harvestable per year = inches of rain per year x 0.623 x your roofs square footage x the price of a gallon of water.

 

The average home in Toronto can harvest the value of $1,080 of rainwater per year = 51” x 0.623 x 2000sqf x $0.01797927/gal.