Friday, April 16, 2010

Should I get a rainwater tank?

At the moment, the SA government is offering rebates to get us onto rainwater tanks.

I'm interested - if I wanted to live off of rainwater, is it worth it?

25000L tank (3.4m diameter, 2.4m high, needs site leveling)
5000L tank (much smaller, can be stuck next to house)
Automatic or manual switch.

After crunching the numbers, it's pretty pathetic. My best bet is to fork out the $2359 for a 25000L tank and get it plumped into my house / site leveled, etc. Based on my current quarterly water usage ($34 actual water usage, the rest is sewerage and supply- ACK!); and assuming that I can get the tank filled from rain 4 times a year (unlikely!); it takes me 23.59 years to get my money back.

Given the roof size of my house and shedding, I wouldn't be able to fill 25000L four times a year.

You can play with the spreadsheet if you like.


Unknown said...

So did you buy the tank?

If you couldn't fill the larger one, doesn't a smaller one make sense, even if it takes longer to pay off.

You don't seem to have allowed for the cost of the money (ie having more money tied up without any possibility of bank interest)

Dan said...

Dead right - I deliberately ignored inflation for simplicity.

For my particular circumstances; the main costs involved are the sewerage and access parts of my water bill - actual usage is tiny.

I did get a solar panel quote; and despite higher initial costs; a 3 kw system would save around 11.5 million litres of water over a 25 year period.

That's a fair bit more than what I could actually capture.

So... that actually looks more appealing in that it will earn me money too!

Unknown said...

*scratches head*
a solar panel would save water?
I thought it might save electricity..

Dan said...

Steam spins turbines generally.

Unknown said...

very subtle :)