29 November 2023

Is rain harvesting worth it?

Whilst we might have known it for some time, recent drought conditions in New Zealand have really brought home the fact that water is such a precious resource that many of us take for granted.

It is only in times when water restrictions are in place that we take a step back and consider what it means when we take that extra-long shower or leave the sprinkler on in the garden. We get so used to turning the tap and having ready access to clean, fresh water.

When we are told that we can’t use it as freely as we have become used to or that we need to reduce the time we spend in the shower, for example, it’s only then that we start to think about the repercussions of our water use and the impact on the environment around us.

Rainwater harvesting in New Zealand is not something new. Many houses, both old and new, still rely on harvesting rainwater in tanks as their only supply of water. Other houses have adopted a hybrid model whereby the property will be connected to the mains, however, they use harvested rainwater as and when they can depending on how much they are able to collect.

During times of drought and water restrictions, more people start to think about the benefits of rainwater harvesting and ask – is it worth it? The question of whether rainwater harvesting is worth it is usually twofold:

·         What will be the impact on the environment and waste?

·         What is the potential return on investment of installing a rainwater tank at home?

In this post, we will aim to answer these questions and provide you with the pros and cons of rainwater harvesting here in New Zealand.

How is rainwater harvested in New Zealand?

Most of us in New Zealand still rely on mains water for our daily water needs. In Auckland, a recent study found that on average, people use between 140 and 170 litres of water a day. This water is sourced from reservoirs that are located throughout the country, making up the majority of the rainwater collection in New Zealand.

Outside of the main dams, reservoirs and rivers that supply mains water throughout New Zealand, many homes are fitted with rainwater tanks that vary in size from 200-litre barrels to 30,000-litre tanks that are typically buried under the ground but can also be stored above ground if room permits.

These rainwater tanks found in domestic properties help to reduce the pressure on the mains water supply but also help to reduce your own water costs and over time, a rainwater tank will pay for itself in the money you save on your water bills each month.

The benefits of harvesting rainwater

The benefits of harvesting rainwater are twofold: environmental and economical.

From an environmental perspective, rainwater harvesting is a simple and sustainable way to protect our planet’s natural resources and delicate ecosystems.

When we use harvested water, we conserve groundwater, save energy, limit the damaging effects of stormwater runoff, and bring out the best in our lawns and gardens.

Environmental benefits of harvesting rainwater

Conserves groundwater

As the global climate changes and drought conditions become more prevalent including here in New Zealand, some urban areas, farms, and industrial sites are turning to groundwater extraction to meet the growing demand.

This type of water sourcing can be destructive. Groundwater aquifers can be tainted with fertilisers, pesticides and other chemicals and the more groundwater we use, the more concentrated these pollutants become, decreasing the overall quality of the water.

Harvesting rainwater means less reliance on groundwater supplies, giving aquifers the opportunity to refill.

Reduces energy consumption

The energy required to keep our mains water flowing is significant. That water has to be treated and piped and this places demands on water treatment plants, pumping stations and the machines that are used to repair the sewer and water lines.

Whilst these resources are well spent on ensuring we all have access to clean water in our homes. Potable (water suitable for drinking, washing etc) does not need to be used for flushing the toilet, washing your clothes or watering the garden.

By harvesting rainwater for these non-potable uses, we can help to reduce the strain on the mains system and reduce the amount of energy needed to keep powering our mains water supply.

Reduce stormwater runoff

Stormwater runoff can lead to a wide range of issues. Due to growing urbanisation, stormwater runoff is becoming a much bigger problem, with water that would previously have been absorbed into the ground now having nowhere to go thanks to the large amount of concrete and asphalt in and around our major cities.

When that rainwater remains on the surface, it sweeps sediment, metals, pesticides and fertilizers into the catchment areas which can pollute lakes and rivers, cause illness for humans and livestock and lead to the decline of some aquatic species.

Low lying areas can also be subject to flooding if stormwater has nowhere to go, causing further issues including subsidence and erosion.

Harvesting rainwater helps to reduce the strain on stormwater systems and prevent debris from entering the watershed.

Economic benefits of harvesting rainwater

Reduce water bills

The most obvious benefit of harvesting rainwater is the money you will save on your water bills each month. Depending on the size of the rainwater tank that you install, you can use the water you harvest for a variety of tasks, from watering the garden to providing the majority of water you use for drinking, showering and cooking.

Even a simple rainwater barrel can save you money if that water can be used to water your garden instead of relying on your mains water supply. This is especially true in years where water restrictions are in place, allowing you to water your garden all year round.

Halt rising water costs

Whilst you might see a direct benefit in terms of costs savings by utilising the rainwater that you harvest from your property, installing a rainwater tank can have wider economic benefits.

By reducing the strain on the mains water supply, you can help to lower the cost of pumping and treating that water. As rainwater tanks become part of the water harvesting ecosystem, the overall infrastructure cost for water management will also go down.

The cons of harvesting rainwater

Whilst there are many benefits of harvesting rainwater, there are some cons that need to be considered.


The upfront cost of installing a rainwater tank can be prohibitive, especially for commercial properties. Domestically, large rainwater tanks that are used as an alternative to mains water can also be expensive to install.

When you are considering whether rainwater harvesting is worth it, it is good to understand the potential return on investment of your tank. A simple rainwater barrel for example might cost you as little as $100 and you might see a return on investment in a couple of years depending on how you use the water around the garden and outdoors.

A large 30,000-litre tank will cost you in the region of $3,500 and up and this investment can take longer to see a return. Water bills, on average are between $20-$40 per month meaning it could take up to 10 years to see a return on your tank (and that’s before you factor in the cost of installation that can add another couple of thousand dollars to the total installation cost). Still, if you are planning on living in a property for that length of time and beyond, this could still represent a good investment in the long term.


Whilst a lot of rainwater tanks are fairly low maintenance, there is still work that needs to be carried out regularly to ensure the quality of the water you are collecting – an issue you don’t have to worry about with mains water. Keeping gutters clean, ensuring there are no leaks and checking the quality of the water are all regular tasks that need to be carried out and can take time.

Unpredictable rains

Whilst it’s great having the ability to capture the rain that falls, especially during the wetter months in winter and autumn, unpredictable rains over the past decade mean that there is no guarantee that enough rain will fall to fill your tank to its full capacity.

With properties that rely on their rainwater tanks as the only supply of water, this can mean you incur further costs to top up the tank in drier years.

Storing your tank

If you want to maximise your rainwater harvesting, you will need a large tank. Storing that tank can be problematic. Whilst underground storage is ideal, retrospectively installing a tank underground can be extremely costly and disruptive and so the majority of tanks installed at existing properties tend to be above ground and these can not only require a lot of space, but they can also look unsightly.

Whilst water tank designs are improving, with a move towards slimline tanks that can be positioned against properties, they still require a decent amount of space and it’s not always easy for properties to accommodate them.

Is rain harvesting worth it – round up

Whilst there are pros and cons to installing a rainwater tank, we believe the benefits far outweigh the disadvantages and that over time, most people that install a rainwater tank will see a return on their investment as well as having access to their own water supply in times of water restriction.

As urbanisation in New Zealand continues to grow, placing increasing pressure on our mains water supply, those that have been early adopters of rainwater harvesting will really feel the benefits over the coming years as water restrictions become more commonplace in New Zealand.

If you already have a tank installed or you are thinking of installing a tank, a great addition is a water level meter that will enable you to see how much water is in your tank at any time. These are particularly useful for large tanks that are used as the main source of water for a property, however, they can be installed on a wide range of water tanks.

At Smart Water, we have engineered the most advanced tank level indicator available that now offers full cloud connectivity. 

Easy to install yourself, your Smart Water tank indicator provides you with all the information you need from our app or from one of our LCD displays. Find out how much water you consume on average from your tank, accurate pressure data and estimates on when your tank will run out of water based on current usage.

Find out more about our range of products or check out our FAQs for more information.

Related Articles

·         Collecting and using rainwater – a beginner’s guide

·         Can you collect rainwater in New Zealand?

·         Should New Zealand be more proactive in collecting rainwater?