Water Harvesting System vs Solar Panels? Which ones pays for itself the fastest?

a1234555

I've been wondering whether a water harvesting system which connects to 2 toilets, outdoor tap for garden and washing machine (I think I managed to convince the missus to connect it to the washing machine if we get it) would pay for itself faster than solar panels where the install costs about the same ££. 

We had solar done last year and the scaffolding alone was about £1k. We were told our panels (and battery) will pay for themselves within 11 years or so but i heard they can pay for themselves in 9 years nowadays. With the rainwater harvesting system there is no need for scaffolding but you do need to dig for it...

I was wondering If one was to decide between panels and a rainwater harvesting system, which one would pay for itself faster? 

I came across some info that on the washing machine alone, a family of 4 could save 20k litres per year. With 2x toilets connected and an outdoor tap (we almost never use ours since we have a water but but in occasional dry spells in the summer we resort to the outdoor tap), how fast could it pay for itself?

subjecttocontract

Well in my case, I have a water meter & my total water/sewerage bill is only about £350 a year. So there ain't much to save on the water bill is there. Whereas with electric I have solar panels (no battery), I export to the grid so my total annual savings are about £600-£700 a year. Electricity savings win hands down every time.

Rodders53

We have a water harvester that was installed during the build of this and five other homes on a small development.  It has a tank buried in the garden holding some 3-4000 litres.  That needs a big hole digging along with drainage pipework alterations.  Not cheap to do after a build. 

That tank runs out in drier months and then mains water is used to automatically part-refill the tank for normal use.  (Or one can by-pass the tank and mains pump to use mains water until the rain comes again).  The last year or two we've not run out, though.
There are alternatives to storing water to the underground system I believe.

It's plumbed to the washer area (but also has H & C taps available).  The whole house had a softener added later.  I'd not want to wash clothes with the harvested water at low temps judging from the toilet flush water residues in the bowls.  SWMBO would prefer the limescale!  Potentially better filtration would help, but would need more maintenance / cleaning.

I reckon with just the two of us it saves around half our water bill.  We now consume around 3 cu m per month and that costs us £240 per annum (inc sewerage).  It was 6 cu m per month in our last home.

Operating costs are for the electric pump and repairs / replacements.  At least one neighbour no longer uses their harvester.  The submersible pump consumes around 800 Watts when running, for around 2-3 minutes every flush of 6 litres?

Car washing is almost streak free from harvested water.

I'd suggest solar is far less disruptive and more likely to be a better investment.  Storing rainwater in a few large butts makes sense for watering the garden and perhaps washing the car and would likely be relatively cheap to do.

Albermarle

Saving £20K litres of water a year, would probably reduce your bill by about £100 pa, or thereabouts . So unlikely to payback in for a long time.

twopenny

I've found ways to save on my water bill, including baths and hose pipe because I grew up with people who had a well and tank so I'm well under the average.
But you'd have to train a family 

I have yet to find a way to save on electric.
So yes, I'd say solar if you have the room and right facing roof.  Room for a turbine.

Slinky

No way would I wash clothing or even the car in water that's harvested from our roof unless there was a seriously good filtration system in place. The grit off the tiles, the bits of moss and bird poo that collect in our water butts show me it's good for nothing more than watering the garden, or perhaps flushing the loo if you don't mind the issues described above.

edwink

We have a rainwater harvesting system set up here that we installed ourselves and also solar panels.

METERED WATER.....We are on metered water use here so we installed 2 x 1,000ltr rainwater harvesting tanks outside in our front garden which is fairly enclosed on level ground and these tanks are hidden inside a wooden low type shed with a door that opens on the front of each tank so we can check the water levels when the weather is dryer. Also this low shed roof has two flap up type entrances for us to be able to fill tanks up ourselves although both tanks are connected together. The reason we put two flap up entrances in the roof was to enable us to gain access to both tanks should they need cleaning out.  We have only ever hoovered both tanks out once and that was about 5 years ago. This was done with a pond hoover and the waste water was just let to run onto the front garden as the front garden is long and slopes downwards. These tanks collect the rainwater that falls on the house obviously but we also linked them via pipework from the bath, shower and wash hand basin from the bathroom which is also at the front.  So even in drier weather these tanks still get filled from having a shower or a bath.  We have only ever run out of water once in the summer in 9 years.  So when that happened we pumped the water from all of the 6 x 100ltr water butts that are sited down the side of our house that collect rainwater from our house roof and also our single storey rear extension. We use a pond pump to do this and just lower the pump into each water butt but not right to the bottom and connect a long hose from it to one of the rainwater harvesting tanks to fill up with the total of around 500ltrs.  Those water butts are always full all the time mostly.  So we have never run out of water to do this.  Once in 9 years is pretty good, we think.  But, the more people living in a house and using the shower or the bath with this type of set up could or would stop this being needed because of extra shower or bath use.  But, of course the 2 toilets would need to be flushed more too.

For the 2 x 1000ltr rainwater harvesting tanks we have a DAB Well Pump in the nearest to the cloakroom harvesting tank and the electrics for this pump are through a vent in the living room wall and just plugged into an electrical socket by the vent. Off the top of my head I think the DAB Well Pump is 600 or 700 Watts and runs for about 1 minute after flushing one of the toilets.  As we have solar panels also we flush either of the toilets when the solar panels are awake and only if really needed at other times. So all of our loo flushing is covered by the rainwater, bath or shower water and covered electric wise by our solar panels. About twice a year we put a couple of bottles of bleach into one of the harvesting tanks to keep it fresh. With the tanks being enclosed they do not get any daylight or sunlight at all. We also have the facility to switch back over to mains water supply for the toilet flushing too just to be on the safe side so we can cover the amount of water needed, but we have never had to do this ever.

We have several filters positioned in the guttering to collect leaves and moss on the edges or corners and clear these when needed once a year.

SEWERAGE....With the sewage part of our water bill we receive an abatement because we deal with our own grey waste water. We had a large soak-a-way put under our patio before the patio was laid. This soak-a-way takes the water from our kitchen sink, washing machine and dishwasher. This is filtered via an old 2nd hand pond filter tank that is sited at the side of the house on the other side of the wall where the kitchen sink, washing machine and dishwasher are. This grey waste water goes into the tank and gets mostly filtered through washable sponge sheets and only some sediment settles in the bottom of the pond filter tank and is cleaned out once a year. Then the grey water runs along a 2" drain pipe down the side of the house to the back garden rainwater gully and is filtered again via netting which is tucked in at the very start of the soak-a-way gully. The grey waste then travels down the gully where there is a round cylinder filter that just slots into the soak-a-way entrance and the waste water goes through that and along another pipe which directs the grey water away from the house, this pipe has a left hand bend at the end with another pipe attached and this directs the water into the soak-a-way itself.

So for our water bill we have metered water costs and have a very large discount on the sewage side of it for having a soak-a-way. We only pay the sewage side of the bill for flushing our toilets as we can not deal with toilet flushing waste water ourselves.

Our average water bill is around £100 a year as we only pay for the amount of water we use and get we only pay 14% for sewage. 

It is not as complicated as it sounds to be honest and we have definitely covered the cost of installing everything many, many times over. The 1,000ltr tanks are the white opaque liquid farm tanks incased in metal frames. We were actually given those by a friend but they are widely available to buy online with a delivery charge. The Well Pump was around £160-£200 I think off the top of my head but this was over 9 years ago now when we bought it. It's a DAB Divertron pump. The pond filter tank was given to us by a neighbour which was formally used in their big pond and doesn't need electric to deal with the grey waste water so has no running costs. It is sited 3ft higher than ground level which allows the grey waste water to flow freely downwards to the soak away gully.

Hope that is some help.

Edwink