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659 posts

Ultimate Geek
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Topic # 160637 14-Jan-2015 10:43
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Potentially looking at going off grid this year or next year and was wondering how much solar you can buy for around $40,000 (mabey $50,000) Would that be enough to do sizable array and battery bank for powering a largish modern home ?

- LED lights installed
- Solar hotwater & underfloor heating, Bottled gas Rinnai systen for winter hotwater
- Gas hob
- Fireplace for heating

Location (Tauranga), N/W facing, no shade. Anyone here doing the solar thing ?

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Uber Geek
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  Reply # 1213644 14-Jan-2015 10:51
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Something like that would certainly be possible with a 40-50K budget, but I have a couple of questions,

 

 

Fireplace?, surely you mean wood burner at a minimum,

 

 

Also is it a new build, so could you look at a wood burner with a wetback to help with the underfloor heating over winter,

 

 

Also what is the demand profile likely to be

 

 

Two retirees at home suring the day?, or workers out of the house during the daylight hours, or family with kids

Dishwasher/large TV, washing machine Dryer, etc etc

 

 

 

 

Grid tied or cut the cable,

 

 

 




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Ultimate Geek
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  Reply # 1214648 14-Jan-2015 11:38
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wellygary: Something like that would certainly be possible with a 40-50K budget, but I have a couple of questions, Fireplace?, surely you mean wood burner at a minimum,

Also is it a new build, so could you look at a wood burner with a wetback to help with the underfloor heating over winter,

Also what is the demand profile likely to be
Two retirees at home suring the day?, or workers out of the house during the daylight hours, or family with kids

Dishwasher/large TV, washing machine Dryer, etc etc Grid tied or cut the cable,


- Open fireplace \ wood burner, with supply of free wood.
- Existing build

High demand profile. 4 adults, 1 toddler, 1 baby, quite a bit of social activity on weekends (family coming over and staying)

- Big TV + Home theatre (mainly used at night for 2 hours)
- Mainly LED lighting
- 2 x laptops (charged during day and run off battery at night)
- dish drawer (can be run during day)
- washing machine (can be run during day)
- dryer (occasional use only)
- water pump (for spring water system)
- sewage pump (for septic tank)

Initially would look to keep the cable to network. But 3-4 years from now would like to add some extra panels and batteries. (say another 20k worth) and go completely offgrid.

Decided this year im over the hustle and bustle of modern life, plan is to cash up, move to the family farm, change my career and spend less time living a modern city life.

Eventually grown more of my own food, get outdoors more and reduce my living costs.





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Master Geek
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  Reply # 1216368 16-Jan-2015 22:15
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I've been off grid for going on 9 years now.

What you propose looks doable but you need to work out how much power and how much energy storage you really need.

Make a list of EVERY electrical device you've got, how many hours a day it gets used and how much power it draws (and hence how much energy it consumes).

You need to be able to generate that much energy in 4-5 sunny hours a day.

If and when you want to go off grid you want enough usable battery capacity to keep you going for three consecutive sunless days and you're going to need a backup generator regardless. Realise that batteries' usable capacity is less than their rated capacity - at least if you want them to last.

How efficient is your fridge? freezer, if you've got one? washing machine? (especially important with two preschoolers) How much juice do the TV and theatre setup take?

Prices of photovoltaic panels have plummeted, switchgear has come down, batteries are still very dear. Unless there is a breakthrough in battery technology, you may find that when you want to cut the cable, your entire budget is swallowed by the batteries.

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Master Geek
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  Reply # 1216375 16-Jan-2015 22:34
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How much do you spend on power per month at the moment.  Am I right in thinking that a switch to solar is more about the feel good factor than economics?  I looked into it for my place.  I really really wanted it to stack up but it just didn't.  I'd never have to spend a cent on power with the return I could get on 50K with some pretty ordinary investments.

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  Reply # 1216389 16-Jan-2015 23:55
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You also need to consider how much current (inverter) capacity you need. As a standard residential power connection can provide 63A continuous. And could most likely provide 100A for a second or 2 (peak capacity). This is 15.1kW Cont and 24kW Peak. Which I only pay $25.86 per month to get. (Cost of fixed charges on powerbill) This is equivalent to renting an inverter of the same capacity for the same amount per month.


A rule of thumb is that it is cheaper to spend money on reducing power consumption when you are "off grid". Than it is to build a bigger "off grid" power supply system. But this then means that it is cheaper again to simply remain connected to the grid but still take steps to reduce your power consumption.

You also need to say what your exact motivation for wanting an "off grid" system is.
-Save money?
- help environment?
-Be self sufficient?
-Be prepared for an extended power cut?
- Need "always on" power (Be prepared for short as well as long power cuts)?

As your answers to the above will make a big change to what the best thing to do will be.

I have an interest in this myself. As the street that runs parallel to mine had a phase fail and 1/3 of the houses had no power for 3 days. (almost 50 year old underground cables) The underground mains cable to my house is 45 Years old. Direct buried neutral screen approx 60M long. 2 other houses in my street have already needed to replace theirs. The street cables have had a few failures over the years as well. Including at least 1 neutral failure to make things interesting. And then there are the power cuts in Christchurch due to the earthquakes. And in Samoa due to the last big hurricane. (I have friends living over there)

Had to run an extension cord to 1 of the neighbours so they could get some power when the phase failure happened. I have a 12v battery backup system for my router, Wifi Ap ect. That has 200 Amp/hr storage.  And a 3 phase generator. I will also be adding some solar panels to the backup system to allow it to cope with long outages. And to reduce the power bill. Main motivation is backup. Any reduction to the bill is a bonus. Will probably need to get the neighbour to repay the favour when my mains cable eventually fails. But I don't know if my mains cable is at "end of life" Or if it will easily last another 20 years.





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  Reply # 1216411 17-Jan-2015 07:21
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Perhaps you should spend the first year grid connected with solar but without batteries, analyse your data, then decide if you can go off grid. The first year you'd contribute back to the grid, even though your payback rate may not be great you're testing the viability in your exact location/circumstances. You might discover with a lot of washing machine and drier use in the winter it's not viable, or you need to modify things - best to discover that when you have options without firing up a generator (which btw are moderately expensive). You will get many of the benefits, lower initial cost, battery technology will improve slightly, and one year won't make much difference in the long term.






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Ultimate Geek
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  Reply # 1216412 17-Jan-2015 07:37
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Bobdn: How much do you spend on power per month at the moment.  Am I right in thinking that a switch to solar is more about the feel good factor than economics?  I looked into it for my place.  I really really wanted it to stack up but it just didn't.  I'd never have to spend a cent on power with the return I could get on 50K with some pretty ordinary investments.

What he said...

I understand where you are coming from (I'd be doing it in a flash if it was remotely viable) but the technology is still a long way away from being economic to do this. Put the money in the bank and use that to pay your power bill. That way you can save the money for when it is possible (still at least 5-10 years away imo) and then go off the grid. 

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Ultimate Geek
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  Reply # 1216413 17-Jan-2015 08:00
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Most of the economically viable case studies that I have seen where off-grid is above break even generally involve new builds with significant costs required to connect to the grid, usually due to remoteness.

I agree that solar-wise it would be wise to start with a grid-tie solution that has a pathway to being off-grid down the road.  As Timmmay says, it'll give you time to better understand and adapt your consumption patterns.  It will also give time for PV and battery technology to improve and for costs to fall.  Personally I'd convert any open fireplaces to woodburners and develop a comprehensive energy plan before touching solar.

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Ultimate Geek
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  Reply # 1216414 17-Jan-2015 08:15
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I have 2 aquaintances that are off grid. The reason they went off grid was that it cost the same to install a multiple system (Solar panels, solar hot water, gas cooking, windmill and small hydro) as it would have cost to connect to the grid, about $40k several years ago. Well planned with extensive research and seeking out efficient appliances. I.e a european deep freezer etc, etc. One of them had a blackout when all of their adult kids and grandchildren came for a wet Christmas a year or so back, so even the best planning is not foolproof in that situation.

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Ultimate Geek
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  Reply # 1216459 17-Jan-2015 11:13
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Interesting thread & replies - like OP, we'd like to get rid of our reliance on the grid.

We'd like to do it soon. We've been waiting & watching, but with technology & pricing changing so fast – just like computers & phones - the longer we hold off, the cheaper & better the equipment gets.
It seems there's no one size fits all solution, and careful design & planning is the key to success.
We're in the middle of an audit of our power usage over a year, will project that into the future to come up with a system.

Right now it looks as though there will be no real cost savings. The issue pushing us is our lack of mains supply reliability. We had 11 power cuts last calendar year, ranging from ½ hour to 7 days (!) that's pretty standard for where we are. 
Our present solution is small emergency battery bank/inverters and larger generators, lpg kitchens & solar/wetback water.

Three nearby properties are producing their own power - all with different solutions. We've been watching, and mucking in to help with their issues while we learn more about what's required. 
With several years of operation under each of their belts it's been interesting seeing if their initial budgets & costings were accurate.

Two of the places are new(ish) & were built to purpose "off grid" & one was originally mains connected, but now it's kept as their backup/emergency supply.
One friends place, Hukatere Lodge - a commercial business - is purpose built solar. One neighbour's wind and solar - the other's solar & solid fuel (with some wind assistance).

Even with their overall design differences they've plenty in common (battery banks, inverters, diesel backup gens etc..) 
They're all trying to live comfortably, dishwashers, TV, internet, hot showers & good lighting, not compromising livability..

Their maintenance & running costs, downtime, equipment suitability (& obsolescence) are getting clearer with time.

Lead acid storage batteries have been the biggest expense & failure point for each of them. All initially underestimated the maintenance & replacement costs of those.
Generator maintenance costs have hurt as well, there's been one replacement & one complete rebuild within 10 years of installation.. both had budgeted on them lasting 20 years.


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