Solar Power Self-Consumption

Solar power self-consumption is an excellent way to maximise your energy bill savings, particularly in New Zealand. Let’s find out what self-consumption means, how it works, and why it’s important for Kiwi homes with solar panels on them.

What Is Solar Power Self-Consumption?

In simple terms, solar power self-consumption means using the electricity your solar panels generate in your own home, rather than sending it back to the grid.

If your solar panels are pumping out power and you're running appliances like a dishwasher, washing machine, or heat pump at the same time, that energy goes straight to your home use — for free. If you're not using it, the excess gets exported to the grid and you earn a small credit.

This concept only applies to grid-connected solar systems, which make up the majority of home installs in New Zealand.

Why does self-consumption matter? Because of the price difference:

• You pay retail rates for grid electricity (typically 30+ cents per kWh).
• But you only earn a solar buy-back rate when exporting (often 8–16 cents per kWh).

So, the more solar energy you use yourself, the better your savings. For every unit of solar power you self-consume, you’re avoiding buying expensive grid electricity.

Kristy explains what solar power self-consumption is;

Why Aim For Solar Power Self-Consumption?

The best way to answer this question is to let the numbers do the talking. The average cost of one kWh of grid electricity in New Zealand, as of late 2024, is over 33 cents. On the other hand, the average price paid for one kWh of exported solar energy is around 15 cents.

Put simply, the cost of the electricity you buy is four times the cost of the electricity you sell! Without getting into the policy details, it’s clear that exporting a lot of solar energy will simply reduce your returns and extend your payback period further.

The smart move, therefore, is to consume most of the solar energy yourself. Every kWh of solar energy consumed on site prevents the purchase of a kWh from the grid, saving you around 33 cents. This is the only case in which the value of your solar energy equals the value of your grid power.

Power Consumption Vs. Solar Power Generation

In a typical New Zealand household, most energy/power demand occurs at the start of the day (when people are having breakfast, getting ready for work, etc.) and at the end of the day (making dinner, using lights, heaters, etc.). 

Check out the energy usage graph below, which shows power demand as a purple line. In contrast, the majority of solar power generation happens around the middle of the day, as seen in the yellow bell curve.

As you can see from the graph above, the peaks for solar generation and power demand happen at different times, meaning most of your appliances are not in use when you have the highest amount of available solar energy. In a typical scenario, solar self-consumption is relatively low (shown in the light blue shading). 

It shows that peak power is being drawn from the grid in the morning and evening at the expensive energy retailer price of around 33¢/kWh (light purple shading). There is also a considerable amount of solar power being exported to the grid at the low rate of around 15¢/kWh (light yellow shading).

Note: If panels are on an east-facing roof, they will generate more power before noon. Likewise, panels on a west-facing roof will generate more power in the afternoon. This factor will change the dynamics of self-consumption. 

Self-consumption is a good goal to work towards, as you can see from the below graph..

The graph above is a scenario that could achieve higher solar self-consumption. The dishwasher is programmed to turn on at 10 am, the washing machine is programmed to turn on at 12 pm, and battery devices (such as an iPad or vacuum) start charging around 1 pm. At 2.30 pm, the heat pump is timed to turn on to start warming (or cooling) the house to achieve the perfect temperature for when you arrive home.

Because the daily power demands have shifted to the middle of the day, less power is used at night, which would save you money by reducing the purchase  of electricity from an energy retailer.

How do you achieve solar self-consumption at home during the day?

Solar self-consumption is easily achievable, especially if you are at home during the day. If you have monitoring on your solar system, take note of when solar power is being produced and aim to turn on appliances at that time, such as vacuuming, dryers, heating, and others.

Charging electric vehicles is another great option to soak up that solar power. You can get a used but decent small electric car for around $10,000. Just plug in your EV when the sun is out and fill the battery up with solar goodness.

How do you achieve solar self-consumption when you're not home?

Technological advancements in recent years help you achieve higher solar power self-consumption using automation, even when you're not around to save power yourself. Using appliances with delayed start times, such as modern dishwashers or washing machines, can help you use solar power directly.

If your appliances don't have delayed starts, plug-in timers are a great option and come with a wide range of functionalities. For example, you can buy the HPM Plug-in Digital Timer from Bunnings at $25, allowing you to schedule your appliance to turn on and off at different times of the day for 7 days a week.

However, a regular timer is not recommended for a hot water cylinder, as the hot water cylinder must stay above a certain temperature to avoid Legionella bacteria. Specifically designed timers or solar power diverters must be used for hot water cylinders.

Solar Power Diverter

A solar diverter turns on your appliances when the sun is out, even when you're not at home. The diverter is alerted as to when and how much solar power is being generated. A hot water cylinder is an example of an appliance that you can connect to a solar power diverter. This is because your cylinder can store hot water for extended periods of time, essentially becoming a type of energy storage device. 

More advanced solar power diverters enhance your solar power generation by sending solar power to pool pumps, washing machines, freezers, heat pumps, and a multitude of appliances. 

Solar Power Diverter Products

Let’s look at some interesting solar diverter models on the market.

• Power Genius: The Power Genius goes a step further and allows appliances to be controlled through a wireless network (the hardware is either plugged in or hardwired), and there's virtually no limit to the number of appliances you can control and monitor. The retail price for a Power Genius starts at $650 for monitoring and from $1100 for the appliance controller. For a typical, 3kW system, it will add $500 to $600 value each year for a 3kW system — a great money saver!
• Green Catchpower: Priced at $800, the ‘Green Catch’ (as the makers nickname it) is another diverter worth considering. Besides the regular job of diverting excess solar energy to your hot water cylinder, the Green Catch’s noteworthy feature is the control pad, which allows you to boost the heating, especially during shorter, winter days.
• Fronius Ohmpilot: The Ohmpilot is a ‘secondary regulator’ from renowned solar electronics brand Fronius. It promises to use even the smallest amount of excess solar energy for heating water. At $1,800, the Ohmpilot is a bit more expensive than the other options, but Fronius is like the Adidas of solar inverters and supporting equipment, which makes the price worthwhile.
• Myenergi Eddi: Myenergi claims that its Eddi is ‘New Zealand’s #1 solar diverter’, which may well be true when you consider the device’s features. The Eddi comes in both single and three-phase capabilities, and also has intelligent daylight-saving time adjustment with overload and short-circuit protection. It can divert power to any heating device up to 3.68 kW. Plus, it also has an LCD display showing all essential information, such as available excess energy, heater temperature, etc. 

Battery Storage

Batteries are becoming increasingly common in New Zealand’s solar power systems. Increasing solar power self-consumption by storing energy in batteries is becoming the new normal. Stored solar power can be used at any time of the day or night.

Battery systems have historically been expensive, but battery storage technology is improving and becoming significantly more affordable. It's one of the most rapidly developing technologies on the planet!

Lithium-ion batteries contain highly recyclable materials, but the facilities aren't yet available in New Zealand torecycle batteries today. But just as solar panel recycling centers are starting to pop up, specialist recycling centers will become commercially viable by the time today’s batteries start reaching their end of life. 

If you choose to purchase a grid-connected system, and if batteries are not in your budget, you can easily add batteries to your system in the future.

One battery making waves in New Zealand right now is the SigenStor by Sigenergy. It’s an all-in-one energy storage system that brings together a hybrid inverter, battery, EV charger, and optional solar inputs — all in one tidy-looking unit. It’s designed to be flexible, future-proof, and super easy to scale, with storage ranging from 5 kWh all the way up to 48 kWh. Whether you're powering a home or a small business, it’s a solid option for anyone keen to make the most of their solar power and boost self-consumption.

And here’s the Tesla Powerwall 3, Tesla is one of the solar industry's biggest innovators, being renowned for its reliable quality and modern specs.

View more battery storage options available in New Zealand here>

West and East Facing Solar Panels

Installing panels on both east and west-facing roofs stretches out the usual midday solar spike into a much smoother, all-day power curve — think more “slow burn” than “sudden burst.”

The graph below shows how your self-consumption improves even without batteries. Just add a few smart devices into the mix, and suddenly you're using way more of your own solar power, leaning less on the grid, and exporting less. It’s a smart, sun-chasing strategy that makes the most of your roof — from sunrise to sunset.