Water Heating

Introduction

Water heating makes up around 30% of an average home’s energy load, coming in just behind space heating (if you don’t include vehicles). This makes it one of the key appliances to electrify. The humble water system also brings one of the biggest opportunities in our energy transition. This is because it can reduce gas consumption significantly and can act as a ‘thermal battery’. This means you can often choose when to use the energy to heat water and time it for when it’s cheapest. If you have solar panels and an electric water system, you can effectively heat your water at very low cost with very low emissions. Hard to argue with that!

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Electric Hot Water Heat Pumps

Heat pumps use a technology that transfers heat from the surrounding air to heat the water, making it incredibly efficient. Many New Zealand homes have a gas or electric resistance system. However, it is the electric heat pump that will bring the most energy bill savings. While heat pumps are more expensive to buy, they are incredibly cheap to run, resulting in major savings over the long term. 

Why choose electric heat pumps?

• They use less energy: Heat pumps are really efficient and typically use 65 -75% less energy compared to electric resistance heaters or gas hot water heating.
• They’re cheaper to run: Due to their efficiency, heat pumps are by far the cheapest hot water system, and they’re even cheaper with solar. 
• They’re better for our climate: Gas hot water systems use a polluting fuel source to heat water and therefore have the highest carbon impact, while electric resistance systems take more energy to heat water. 
• They require less maintenance: Generally, hot water heat pumps require less maintenance than other systems, with a professional maintenance checks only required every 3-4 years.
• They’re flexible: With a range of features, such as wi-fi compatibility or timers, heat pumps can be used to control household energy loads. This is particularly useful if you have rooftop solar and can choose to heat your water in the daytime.

What to consider

You’ll need to do some research before you’re ready to replace your hot water system to ensure you choose the right one for your home. Typically, the more expensive heat pumps are quieter, use less electricity, have better warranties and use more environmentally friendly refrigerants than their cheaper counterparts. 

We encourage you to consider the following elements when making your choice:

• Level of control: If a model has a timer or wifi/wired control it will enable you to time when you heat your water so it can be run off your solar power. This is the optimal method to heat your water from an emissions and cost savings viewpoint.

• Design: Whether you choose a split or all-in-one (integrated) tank may depend on how much room you have. The split system will have a separate larger compressor that heats water more quickly but takes up more space.
• Efficiency: Look for a high coefficient of performance (COP) rating, indicating greater energy efficiency. The more efficient, the less energy used and therefore lower running costs. Avoid models that have electric resistive elements built in marketed as ‘back-ups’ as this means there is a much higher energy draw.
• Refrigerants: Some refrigerants are greenhouse gases and have a detrimental impact on our climate. CO2 and R-744 refrigerants are good choices for the environment, R-744 is ok, while R410a and R134a should be avoided.
• Warranty: Warranties are complex with different periods that cover labour, tank and parts but generally opt for longer warranties from companies that have been around for a while. Also note that the distance from an approved service agent may add to repair costs.
• Noise: Some heat pumps can be noisy like a reverse air conditioner, so consider your neighbours and how close it may be to any windows or opt for a lower decibel rating (eg. 36db).

Renters

Renters make up around one third of New Zealand households, and are left behind on reaping the full benefits of electric efficient homes. Rewiring Aotearoa, and other organisations, are advocating for better renters rights to rectify this, but fixing the finance so that these technologies are available to everyone and providing incentives to landlords to electrify their properties so tenants benefit is crucial. Whether you’re a renter or not, write to your MP and demand access to electrification finance - and incentives!

In the meantime, renters could present the information to their landlord asking for a hot water system upgrade. Some landlords have introduced what’s called a ‘comfort levy’ to the rent in exchange for lower bills. Using a timer to heat the water, including on electric resistance heaters, is an easy way for renters to lower bills. 

FAQ