Going "off grid" in suburbia

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gchiu

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#236425 1-Jun-2018 11:32

The situation is this. My kid is building a small house on the rear of the section. Not quite tiny but small at 50 m2. On account of various earthquakes, and lack of engineering time, we are now in the 3rd year of the build with only the foundations down. Wellington Water advised us incorrectly on where we could build so we had to shift the house to avoid sewers that are crossing the property when they initially advised we could stradle them. 3 years + for 50 m2 so I really can't see how the current govt can meet their target!

Anyway, I was initially advised that she could take the power from my switchboard so she wouldn't have to have a separate connection ( and therefore line charges for the rest of the life of the house ). But then another electrician told us that the street fuse was rated for 63A, and my existing house had a theoretical maximum load of 95A or something. So, no way was he wiring up the new house to mine. But he suggested that I could go solar for the new house.

But after seeking 3 quotes from various suppliers I am no closer to a solution. She pre-bought some appliances 3 years ago at the start of the project which are still in their original wrapping ( we were given an optimistic time frame by the architect ). This includes a gas top with electric oven.

The plan was to use batteries to keep the load from her house low so that it doesn't impact on mine. And if there were no sunshine, then we'd top up her batteries from the grid overnight. She's going to have a kettle, microwave, fridge/freezer, one drawer dishwasher, vacuum cleaner, washer and dryer on top of the oven. Water is going to be instant gas by LPG.

Is this doable at all? Or should we just bite the bullet and get a separate pole connection?

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#2026860 1-Jun-2018 12:00

Oh, tagging @ARedwood as requested.

I'm thinking we need to ditch the new electric oven at least and go gas on that. And hopefully the architects will have done the job correctly so that she won't any or much space heating.

nickb800

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#2026862 1-Jun-2018 12:02

How far is the cable run from the main house to the 'small' house?

I suspect solar+battery for what you're proposing will be very expensive. Perhaps go with a hybrid option - use gas as much as possible so that your demand on the house power is reduced. This would mean ditching the electric oven for gas, and using a whistling kettle on the gas hob rather than an electric kettle. This would bring your maximum load down, and then you might be able to discuss with the sparky about limiting the circuit breaker ratings on the small house (greater risk that you'll accidentally trip the circuit breaker.

Another option could be to upgrade your house to 3phase power - this will still cost a bit of money, but means you can keep your small house setup as planned.

How much are you thinking about resale value for your house and the small house? Would you be looking to rent it out separately down the track? This may sway you to a more robust option

gchiu

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#2026865 1-Jun-2018 12:10

The distance from my switch board to her house would be about 30m.

Good idea on using gas for the kettle.

What about the other appliances? She's thinking of getting a combination washer/condensor dryer.

She can use a Dyson stick vacuum cleaner.

How does 3 phase power help? ( I'm not that conversant with this stuff ).

No plans on renting out. When we get older, and she starts a family I suspect we'll just swap houses.

Aredwood

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#2026868 1-Jun-2018 12:20

Is the main house all electric? Or does it have gas connected as well?

Consider switching some loads in the main house to gas to reduce the demand on the incoming cable. main one being the stove.

Get a sparky to install a 63A breaker on the cable to the main house. Then you can connect as much as you like. Just try not to use too much stuff at the same time as the breaker will trip. But it will protect the cable against overload.

Do you have night rate power available?

Edit

And is natural gas available?

Also consider future EV charging. That alone could be the decideding factor to get 3 phase power connected. If you do get 3 phase, extend it to the second house as well. 3 phase is actually cheaper over long distances than single phase anyway.

gchiu

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#2026879 1-Jun-2018 12:58

The current house is all electric except the stove which is on LPG. We decided a couple of years ago to rip out all the gas heaters as they were all unflued, and move to far infrared.

Daughter has been eying an EV for a long time but is waiting until her house is built to see if she has any cash left.

What's involved in getting 3 phase power? And what use is it for other than charging an EV and running heavy duty machinery?

gchiu

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#2026883 1-Jun-2018 13:07

Green Spark Solar have just told me that with an extra set of their batteries ( 20 panels on the roof, smart inverter, and a total of 28.8 kWh store of batteries) she would be able to draw 12 Kw per hour which should be enough. So, that's now about $45K installed. Using lead nano carbon batteries which I don't much about but I gather they're lead acid doped with carbon to increase their operating responses.

timmmay

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#2026888 1-Jun-2018 13:16

How much will a new connection to the mains cost? All this messing about will be taking a lot of time and energy, and solar + battery will cost money. It will also impact how the house is lived in. I'd probably pay the money and get the connection.

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wellygary

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#2026897 1-Jun-2018 13:32

timmmay:

How much will a new connection to the mains cost? All this messing about will be taking a lot of time and energy, and solar + battery will cost money. It will also impact how the house is lived in. I'd probably pay the money and get the connection.

OP has said he would like to minimise on going connection charges if possible,

The obvious solution is to have an electrician get the network company to price upgrading the feed to his main board (3 phase if required) or maybe look at uprating the pole fuse ....

This post indicates the second option could be possible but may also require upgrading the feed cable from the pole to the main board,

https://www.electricalforum.co.nz/index.php?action=more_details&id=1472069149

gchiu

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#2026902 1-Jun-2018 13:40

wellygary:

The obvious solution is to have an electrician get the network company to price upgrading the feed to his main board (3 phase if required) or maybe look at uprating the pole fuse ....

This post indicates the second option could be possible but may also require upgrading the feed cable from the pole to the main board,

https://www.electricalforum.co.nz/index.php?action=more_details&id=1472069149

I wonder why it's not obvious to the electricians I've consulted who've pushed me down this path of solar? :(

Time to ask another electrician.

gchiu

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#2026909 1-Jun-2018 13:53

timmmay:

How much will a new connection to the mains cost?

I've emailed several companies that do this. No reply.

Aredwood

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#2026935 1-Jun-2018 14:35

Has your electrician assessed your current wiring for compliance with the voltage drop rules of the electrical standards? Your house is already highly likely to be non compliant for volt drop. And since you already have gas cooking in the main house, you can't switch to gas cooking as a simple way of freeing up some capacity. So you are probably going to have to upgrade your mains cable no matter what.

And if you are going to upgrade the mains cables - Over spec the cables. As the Labour cost doesn't change much to get a bigger cable installed. Most EV models support 3 phase charging. (leaf is the main one that doesnt). And eventually Nissan will have to provide 3 phase support. As try to charge an EV with 100KW of batteries with single phase - not going to happen. Would take 27 hours to do so using the caravan socket that most leaf owners currently use for home charging.

Solar also has ongoing costs. As you have to allow for battery degradation, and inevitable failures of inverters and other equipment. And what do you do when there is a week or more of no sun during winter? Start the diesel generator or have your own mini blackout. Have seen someone say online, that they lived off grid for over 10 years. And in that time the money they had to spend on equipment replacements averaged out to $75 per month. So still more expensive than just paying lines company fees.

Aredwood

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#2026940 1-Jun-2018 14:43

gchiu:
timmmay:

How much will a new connection to the mains cost?

I've emailed several companies that do this. No reply.

Actually phone some companies. There are so many variables with pricing a mains cable upgrade. That someone has to visit. And a big factor is if the lines company asks for a capital contribution or not. So often you won't know the full costs until after you apply for a new connection or capacity upgrade.

And they also have their own rules for various things. Will they allow more than 63A single phase? Or do you have to get 3 phase? How do they define a residential connection? Will having 3 phase mean paying commercial rates for power? (typically high fixed fees but cheaper unit costs). You might actually be better off getting a second connection installed.

gchiu

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#2026974 1-Jun-2018 15:37

Aredwood: Has your electrician assessed your current wiring for compliance with the voltage drop rules of the electrical standards? Your house is already highly likely to be non compliant for volt drop.

The house was rewired by a single company and I assume it's compliant.

Aredwood:
And if you are going to upgrade the mains cables - Over spec the cables. As the Labour cost doesn't change much to get a bigger cable installed. Most EV models support 3 phase charging. (leaf is the main one that doesnt). And eventually Nissan will have to provide 3 phase support.

I can certainly look at doing that.

Aredwood:
Solar also has ongoing costs. As you have to allow for battery degradation, and inevitable failures of inverters and other equipment. And what do you do when there is a week or more of no sun during winter?

The plan was to charge batteries from the grid in the wee hours.

Aredwood:

So still more expensive than just paying lines company fees.

Infrastructure costs are going to go up. They haven't even got enough land to house people they reckon in Wellington. So, I don't mind future proofing a little.

mattwnz

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#2026975 1-Jun-2018 15:38

That solar install looks very pricey. IMO if you are in suburbia, then I think it makes sense to connect to the grid, at least short term. From what I have seen, the big cost with solar and where the payback may not be there, is storage of the power, eg batteries. Many people who get it end up selling a lot power back to the grid, as they don't get batteries. But the buyback power rate is poor, and this probably needs to be looked into. But selling power back isn't possible if you don't have an electrical connection to begin with. You could also look at solar just for water heating.

IMO the building industry in NZ needs a huge shakeup, but it doesn't look like any government really wants to get into that. 50sqm though is the size of a double garage, so I am surprised that it has taken 3 years. Are you on a hill or something. I would have thought you would go underground with the power rather than installing poles, although I am not sure which is cheaper these days.

gchiu

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#2026977 1-Jun-2018 15:41

Aredwood

Actually phone some companies.

Yeah, tried that as well. No one picks up.

Aredwood

Will they allow more than 63A single phase? Or do you have to get 3 phase?

Electrician just emailed me that we could go to 2 phase, one for each house. But I would need another meter and also new cabling probably from the pole to the house.

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