Off the grid solar

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ermat

172 posts

Master Geek

#280000 21-Nov-2020 18:51

I am planning to build new on a rural property. My initial enquiry regarding power connection to the property is telling me power connection from the street is going to be expensive.
If it is, rather than pay a high connection cost I'm now considering off the grid solar.
My initial thoughts are gas infinity water heating and gas stove top.
The house is 150 sm plus external garage.
Am I on the right track, what are my options. Your thoughts appreciated.

Fred99

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#2608078 21-Nov-2020 19:31

Yep - I reckon you're on the right track.

Maybe look at alternate hot water heating options if gas companies don't deliver 45kg bottles to where you are. Cooktops use hardly any - 9kg gas bottle lasts us 3-4 months and fits in the boot of the car, but they won't last very long heating hot water for a house full of people.

If there was a wood supply, I'd put in an Aga wood burning oven with wetback if I was to live off-grid. They're quite well insulated, unlike a wood-burner with wetback, OK to use in summer so long as you can open a window/door.

ermat

172 posts

Master Geek

#2608080 21-Nov-2020 19:46

Fred99:
Yep - I reckon you're on the right track.

Maybe look at alternate hot water heating options if gas companies don't deliver 45kg bottles to where you are. Cooktops use hardly any - 9kg gas bottle lasts us 3-4 months and fits in the boot of the car, but they won't last very long heating hot water for a house full of people.

If there was a wood supply, I'd put in an Aga wood burning oven if I was to live off-grid. They're quite well insulated, unlike a wood-burner with wetback, OK to use in summer so long as you can open a window/door.

I'm not that far from civilization. 45 kg bottles are available so unless there is a better option I would go with infinity hot water. I am installing a log fire, but will probably run with an efficient electric oven if it exists.
I'm not up with the solar options, hopefully someone can fill me in on what's best in that regard.

quickymart

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#2608082 21-Nov-2020 19:49

A mate of mine (who admittedly is still connected to the grid) lives in southern/central Hawkes Bay and he has solar, selling back his excess power to the grid. He said some months his power bills total $35.

ermat

172 posts

Master Geek

#2608085 21-Nov-2020 19:53

quickymart:
A mate of mine (who admittedly is still connected to the grid) lives in southern/central Hawkes Bay and he has solar, selling back his excess power to the grid. He said some months his power bills total $35.

No doubt, unfortunately not in my case as I suspect I'm up for a grid connection in excess of $20k.

timmmay

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#2608092 21-Nov-2020 20:23

I suspect to be completely off grid you will need a fair few panels, and quite a bit of battery storage to cover you for those cold wet weeks where we don't get much sun and you don't get much power. The batteries will need to be replaced periodically. You might also need a generator, a decent sized one in a shed a way's off from the house, with a good sized fuel storage. I wonder how much all that will cost - this website says about $42K, but of course then you don't pay for power. Then every maybe 10 years you'll be up for new batteries, and maybe a new controller occasionally.

You'll not be able to use electric heating, it'll be gas or burning things, neither as good for the environment as hydro power and a heat pump.

$20K doesn't sound so bad.

larknz

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#2608093 21-Nov-2020 20:29

I am in favour of a good solar installation, but you need to consider a couple of things. How big are your batteries and what happens in the middle of winter if you get a couple of weeks of overcast weather. Are you planning on having a generator as a back up

ermat

172 posts

Master Geek

#2608116 21-Nov-2020 21:04

timmmay:
I suspect to be completely off grid you will need a fair few panels, and quite a bit of battery storage to cover you for those cold wet weeks where we don't get much sun and you don't get much power. The batteries will need to be replaced periodically. You might also need a generator, a decent sized one in a shed a way's off from the house, with a good sized fuel storage. I wonder how much all that will cost - this website says about $42K, but of course then you don't pay for power. Then every maybe 10 years you'll be up for new batteries, and maybe a new controller occasionally.

You'll not be able to use electric heating, it'll be gas or burning things, neither as good for the environment as hydro power and a heat pump.

$20K doesn't sound so bad.

I don't know yet, still waiting for pricing.
I suspect it won't be less than 20k but could easily be 40k.

ermat

172 posts

Master Geek

#2608120 21-Nov-2020 21:08

larknz: I am in favour of a good solar installation, but you need to consider a couple of things. How big are your batteries and what happens in the middle of winter if you get a couple of weeks of overcast weather. Are you planning on having a generator as a back up

Yes, generator back up is an option.

Senecio

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#2608121 21-Nov-2020 21:17

Will you be home during the day to use power while it’s being generated. If not then battery’s to store the power during the day when home at night will be very expensive.

larknz

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#2608147 21-Nov-2020 22:29

I understand that a network connection can be expensive, I'm in the industry. But you need to take into account the whole of life cost of an off the grid connection. The life of your grid connection is 50-60 years. What is the total cost of your off the grid connection over this period, taking into account the replacement of solar panels, batteries and generator. Also what is the potential effect on resale value.
As said earlier I'm not against off the grid, but there are some building companies pushing this as an option without doing a whole of live evaluation of the total costs. $20,000 to get a network connection will have a different outcome when compared to $50,000 to get a connection.
I nearly forgot to mention the cost of gas.

kiwigander

231 posts

Master Geek

#2608148 21-Nov-2020 22:40

I've been off grid for fourteen years, happy to share my experience, although your mileage may vary.

To start off, I assume that you want a 'normal' lifestyle: house at a reasonable temperature, all mod cons, not having to worry constantly about how much energy you're using/losing.

Definitely heat water and cook with gas (LPG, I assume; it'd be an odd place to be too far off the grid to connect yet have a natural gas main going right by). I suggest you look for a cooker with a gas oven as well. We've got one of each (i.e. cooker with two ovens): use the electric oven quite a bit in the sunnier months but are grateful for the gas oven when the sun hasn't shone for a couple of days. And definitely an instantaneous LPG water heater (califont). Our califont is a backup to our solar water heater but it does get a fair amount of use.

Look for a large, high-efficiency wood burner as your space heating source. If it accommodates a wetback then, with a small circulating pump, you can supply radiators in other rooms.

Ensure your house is optimally situated to take advantage of the sun (not only for the photovoltaic panels but also for space heating). Insulate as well as your design allows. Double glaze throughout, and if you want aluminium framed windows, ensure they are thermally broken. There is a lot of crap on the market.

However large the generating and energy storage capability the salesman says you need, go larger.

You will want a backup generator. No matter how large your battery bank, you will manage to run it down. I'd advise a small diesel generator rather than petrol; the fuel doesn't go off during longish intervals that you don't use it. (Petrol generators have to be exercised frequently, and the fuel goes stale.)

May I ask what part of the country you're in?

Scott3

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#2608155 21-Nov-2020 23:40

While I am quite interested in small power generation, My gut feeling it that you would be best to go the gird route unless the cost of connection exceeds $50k. (unless you have a hydro resource on site)

But a lot of it will come down to how much you are willing to shape your lifestyle around an off grid power supply.

ermat:

I don't know yet, still waiting for pricing.
I suspect it won't be less than 20k but could easily be 40k.

Hard to make a call on viability without knowing this number.

If it is $20k, I would go on the grid. At 100k, going off grid makes sense. In the middle depends on what your needs are.

I have family members with a $50k on grid solar / battery setup. In winter both space heating, and hot water heading are done via a wood burner. Despite this they are normally drawing from the grid in evenings after cloudy days. (the do have a big house, with 4x fridges or freezers, water pump, pool pump, electric fence machine).

I have some other family members (I think they had an $100k+ connection cost) with a off grid setup. I assume they have added solar now, but initially they had a Generator / battery setup. They were quite budget contained, but needed a big (silenced 1500RPM diesel) generator to run commercial grade welders. I think the setup was capable of running the oven without firing up the generator, but was programmed to start it to reduce strain on the battery bank.

In general, It is to expensive to size an off grid setup to accommodate heating loads (beyond toasters, microwaves & hairdryers). This means you are pritty much stuck with:

Gas cooktop
Gas / Wood space heating
Solar thermal (with gas boost) / Gas / Wood for water heating
Gas tumble dryer (or no tumble dryer)

Ovens are tricky as gas ovens often suck (and some draw a lot of power anyway). Not really such a think as a dramatically more efficient oven, so would need to make the call between a gas oven, no oven, or an electric one (Would need a big solar system or back up generator if you want to use it outside ideal solar times).

45kg gas bottle delivery prices vary, but at $130 each it works out to be 21.2c/kWh. Quite a bit more than I pay per unit of power, and dramatically more than the cost of running a heat pump on grid power. Being a fossil fuel, there is a good bet the cost will increase over the coming decades. How much this matters depends on what sort of lifestyle you want to live. If you are willing to give up the dryer, have gas only as a boost for an evacuated tube solar setup, and only have wood for space heating your gas usage will be small. On the other hand if you want central heating 24/7, your gas bill will be quite large.

Also consider that the UK is banning non plug in cars in 2030, and Plug in hybrids in 2035. If NZ follows them, and you like 0-3 year old cars, in under 20 years you will need to accommodate an ev or two in your setup.

Some indicative system pricing here: https://www.mysolarquotes.co.nz/about-solar-power/off-grid/off-grid-system-sizes/

Entry level off grid setups start at about $15k. This gets you 4 panels, 3kW inverter. This system is good to run an efficient fridge, 4x LED lights, cell phone charger & laptop charger only. - I stayed in a batch on great barrier with such a system. We were being carefull with power (i.e. Watching TV in the dark), but still managed to run it flat on like 3 hours. That had halogen lights rather then LED though.

Personially I would want a $50k system like my family members (tesla powerwall + about 7kW panels). I would also want a silenced 1500RPM diesel generator 6.5kVA- 20kVA. (Cira $10k- 20k) - need to find a single phase one which cuts down used options. I do like the luxury of lots of power, but that setup would mean I wouldn't need the generator in good conditions, but if I had guests, my partner decided to use her 2kW hairdryer of 2 hours, or if wanted to cook a roast while vacuuming on a winter evening, the generator would keep everything running.

What cost your system would need to be would depended on where you sit between the two cases listed above.

In terms of environmental, the NZ grid is one of the cleanest in the world. I would expect being on grid to be greener than an off gird system with heating by gas, and diesel backup.

In terms of ongoing cost, I use a lot of power, spending somewhere between $2500 and $3500 a year. Going off grid would be cheaper in running costs, If we assumed $15k of the system was the battery with a 10 year live, and the other $35k + a $15k generator had a 25 year life, The annualized cost of updating the system long term comes out to $3500 a year. (plus fuel and services for the generator). I spouse you could consider the first round of gear to be free, as it was covered by savings from getting a grid connection.

Also consider if a sweet off grid setup, or a standard grid connection will be more attractive to a buyer when you come to sell the property.

[edit] - other factors are where in the country you are. Grid power is way more expensive in northland than Otago, effects economics.

Also if you are going to go off gird with a big system, the panels take up a lot of space. Your property will want to be designed such that there is sufficient roof space facing the optimal angle and direction for winter (you can look up these tables). Installers seem to have no issue throwing half the panels on a south facing slope, but at best they will do piss all, and at worst they will drag down the entire system.

Also if going off grid, it would be ideal for your house to have great thermal performance - Could lean on the principals of passive house design.

ermat

172 posts

Master Geek

#2608212 22-Nov-2020 06:22

Thanks for the response. Most helpful.