How to go off the grid (or reduce your home's dependence on it)

We're fortunate to live in a society where reliable access to water, electricity, and methods of heating is commonplace.

But as incredible as these systems are, there are some parts of the country they don't reach. And it's not always just remote locations that struggle with access—on some rural properties, for example, getting mains electricity lines connected to a build on a previously undeveloped site can be very expensive.

Even when you are connected to the mains, faults such as power outages sometimes occur; relying on the grid is not a foolproof solution. With today's technology and lower prices, however, greater energy security and self-sufficiency is possible.

Whether you're wanting to design a totally off-grid home, or just want to increase the resilience and self-sufficiency of your power, water, and heating, here's what you need to know.

One of the most reliable ways to generate your own electricity off grid is with solar power. While it depends on the number and efficiency of the panels installed, as well as the storage capacity of the system, in most cases solar power can provide all the electricity needed for a home.

Yet with all things in life, economic and material considerations can't be ignored; more panels and batteries result in a higher price, and there are limitations to what can be generated in certain conditions (less on cloudy days and nothing at night), but with the right design and planning, these hurdles can be overcome.

There are two main things to consider when choosing a solar system: the peak generation capacity (or how much power you need all at once) and how your power use is spread through time.

While it varies by brand and model, the average solar panel can generate around 250 watts in full sun conditions, which could power five 50 watt light bulbs at the same time. But most homes have more than five lightbulbs to power, so more panels will be necessary. Systems often start around 4 kilowatts (kW) (4000 watts) but as long as there's enough room for more panels, they can scale up to whatever output is required.

Peak output is not the only consideration, however. Solar panels only generate power during the day, and the power generated by each panel changes with the angle of the sun and how much cloud cover there is. This inconsistency of generation during the day, coupled with the fact no power is generated at night means power generated at peak times needs to be stored for use when direct sunlight isn't available.

The solution for this problem is to use batteries to store power that can't be used at the moment of generation. Suppose you have a 10kW system and the sun shines at peak brightness for four hours a day. Assuming for simplicity's sake you weren't using any power during that time, each hour 10kW would be fed into your batteries. At the end of those four hours the batteries would be holding 40 kilowatt-hours of charge.

This energy can then be used as required: if you needed to use 10kW all at once, the batteries would last 4 hours, but if you only needed 2kW of power they would last for 20 hours.

Batteries are still relatively expensive but their prices have fallen quite dramatically in the last decade. Prices for lithium ion batteries in particular—the kind found in laptops and smartphones—are becoming more affordable and the batteries themselves more energy efficient every year.

How much energy you need will depend on your individual circumstances. Average daily electricity use varies around the country, but there are some patterns to be seen geographically.

In 2017, for example, the Electricity Authority reported that average daily electricity use on the West Coast was 16kWh per day, compared with 23kWh per day in Canterbury. What accounted for most of the difference was the fact that Cantabrians used electricity for their heating, while on the West Coast wood fires were much more common.

With a solar generation and storage solution installed, is it still worth connecting to the grid? If it's not cost prohibitive, then generally the answer is yes, because doing so gives you the option of selling any excess power you generate to your power company, where it then becomes part of the grid supply for other people.

Buyback rates for solar power are currently similar to the wholesale rates energy companies pay for their electricity from large-scale commercial sources. In some countries, legislation mandates the price energy companies are required to pay for excess solar energy, in an effort to encourage residential solar adoption, but no such legislation exists in New Zealand.

In fact, power companies are not required to purchase solar power at all, and there is no minimum price they have to offer, so be sure to check with various power companies to see what rates they pay (if any) before choosing who to sell back to.

If you're building a completely off-grid system, then buy-back rates won't be relevant to your considerations. But if you have the capability of connecting, it makes sense to, even as a backup, because you can charge your batteries in the event of cloudy days or storms, and the buy back options can reduce the overall cost of the system.

While solar is a popular method for off-grid electricity generation, it's not the only game in town.

If you're in a particularly windy area, a small wind turbine could be another option for power generation. Like solar generation, however, it can't be relied upon to generate consistent power, as once the wind falls below a certain speed, the turbine will stop spinning and power will cease to be generated. Batteries again are the most common solution for managing this intermittency.

Small-scale hydroelectric power generation is also possible in rural areas with access to a stream or river with sufficient flow and consistency. In the right settings, hydro systems of this kind can offer more consistent power generation than solar or wind, though those settings are relatively rare—most homes will not be in a position to take advantage of this option.

A solar system that provides all your electricity needs off grid is possible, but it can be expensive. One way to at least partially overcome the cost of the current technology is to lower your electricity use. Without the need for so much power, you won't need to outlay so much for your panels and batteries.

In 2018, the average home's electricity use broke down as follows: 27 per cent on water heating; 20 per cent on electronics and other appliances; 17 per cent on refrigeration; 15 per cent on space heating; 13 per cent on lighting; 5 per cent on cooking; and 3 per cent on clothes drying, according to data from the Energy Efficiency and Conservation Authority.

For a start, you can minimise the electricity needed for things like hot water and space heating by using different technologies.

Solar hot water systems only use electricity for boosting and maintaining the temperature, and don't rely on photovoltaic energy creation to heat the water. Instead, networks of tubes filled with liquids are placed inside the panel that sits on the roof. These heat up in the sun and the heat is transferred into the water in the insulated cylinder.

We'll come to heating later, but if you can rely on something that doesn't use electricity for heat generation—a wood burner connected to a central heating system, for example—or something that uses electricity more efficiently like a heat pump, then your electricity needs can be lowered further still.

Removing hot water and space heating from relying on electricity could reduce electricity use by 42 per cent according to the usage figures above, which can make it easier for your solar or other power generating systems to manage.

With everything else that can't be substituted away from electricity use, energy efficient options can reduce consumption further. LED light bulbs, for example, in some cases use less than a tenth of the energy a similarly bright incandescent bulb would.

In a similar situation to sometimes inaccessible mains electricity, some properties in New Zealand are not able to connect to a mains water supply. In these situations, tanks are used for storage and rain is either collected from the roof of the house or the tanks are refilled periodically from a water truck.

With the right catchment system, rainwater can be collected from the roof. Instead of funnelling it away into the greater stormwater system like might be done in a town or city, it's instead directed through a debris filter that removes most of the larger contaminants before entering a storage tank.

To make the collected water suitable for drinking, it then needs to be pumped out and run through a filtration and UV treatment system. The exact configurations of these systems differ; some filter the water before it enters the house and the final-stage treatment necessary for drinking is only installed on select taps. Others treat the water at the pump, giving every tap in the house potable water.

Tanks themselves come in a range of sizes, from the hundreds of litres to 30,000 litres or more. The size of the tank that's required in your situation will depend on both how much water you use each day and how the rainfall in your area is spread throughout the year.

If your property is in an area where rainfall is more consistent throughout the year, then a smaller tank may be enough to fulfill all your needs, as it will constantly be topped up throughout the year. Not everywhere in the country is like this, however, with some places experiencing the overwhelming majority of rainfall in a few short months. For off-grid homes in these places, larger tanks may be appropriate in order to store rainwater for longer periods.

That said, water tanks are able to be topped up from trucks if necessary, so it's possible to utilise a smaller tank and have it re-filled if necessary, instead of spending so much up front with a tank that's larger than necessary most of the time.

Like electricity, some of the shortfalls of being on a tank supply can be mitigated by changing your habits around water and making your use more efficient. Water-efficient appliances and flow-limiting taps and shower heads can be effective at lowering water usage without any appreciable difference in effectiveness.

Another way to maximise use from water is to recycle it. Greywater is water that's been used in anything other than the toilet—for dishes, showers, laundry, handwashing, et cetera. With a greywater recycling system, greywater can be used for flushing toilets instead of going straight into the wastewater. As the toilet uses the largest proportion of an average New Zealander's daily water use, it makes sense to use second-hand water and save any treated supply for other uses.

Heating a home off the grid is arguably an easier task than trying to work out how to generate enough electricity or store enough water. While there is no such thing as a centralised 'heat grid,' going off the electricity or gas mainlines do limit heating options to some extent.

For one, gas fire and heaters fuelled by relatively cheap mainline natural gas are no longer an option. Electric heaters can still be used with a large enough solar installation, but it would be a relatively inefficient way to heat a home when electricity is limited by daylight hours and costly battery capacity.

Bottled LPG gas is a workable alternative to mainline natural gas. A common setup is for two 45kg LPG bottles to be installed on your home. You only use one at a time, but having two installed allows for continuous supply after one is emptied and needs time to be refilled. Bottles are replaced by energy providers with specialist trucks, meaning you don't need to travel to a refuelling station.

With bottled gas, you can do everything you could do with regular mainline gas such as heating, hot water and cooking, which can help take some strain off the other systems in your house.

Electrical heating is possible off the grid, but due to its high electricity use should be limited to either ground-source or air-source heat pumps, which don't use electricity for heating directly, which makes them much more efficient.

Wood is a great off the grid fuel for heating, as it doesn't require any complicated installation or refuelling systems. Whether it's a fireplace or a boiler feeding a central heating system, wood provides a cheap, reliable and relatively maintenance-free option for heating.

Part of the solution is, once again, reducing the need for heating in the first place. An off-grid home should also be a high performance home, meaning it's extremely well insulated, takes advantage of passive solar design to absorb heat during the day, and has well-designed ventilation systems.

An off-grid home that ticks all those boxes won't require as much energy to maintain its internal temperature, and will provide a comfortable and healthy environment with relatively few inputs.

Are you ready to start planning your own off-grid home? Get in touch with one of our architecture and design or construction professionals today.

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