@upnorthandpersonal, that’s a serious piece of engineering. Designing and building a 14kW ground-mount array with 120 kWh of storage (heading toward 200 kWh) is not a hobbyist setup. 🤣 

A few obvious questions come to mind. How far are you from the nearest town or grid connection point? In other words, was this primarily an economic decision, a resilience decision or simply geography making the choice for you? At that latitude, winter solar yield is marginal to negligible I would imagine, so your storage capacity is clearly about buffering seasonal shoulder periods rather than bridging the full winter. I’m curious what your annual consumption profile looks like in kWh, and how much of that is thermal versus electrical.

On the generator side, how much bio-diesel are you actually producing per year, and what does winter charging translate to in litres per month? Charging ‘once or twice a month’ suggests your baseline winter electrical demand is relatively disciplined. Are you running the generator purely to charge batteries at high load for efficiency, or also covering direct loads simultaneously? It would be interesting to know the generator size and your typical charge rate into the battery bank.

And how are you handling water supply and wastewater off-grid… drilled well, filtration, grey-water treatment?

Posted by: @editor

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How far are you from the nearest town or grid connection point? In other words, was this primarily an economic decision, a resilience decision or simply geography making the choice for you?

Actually not that far, however, the cost of my initial system (10kW solar and 28kWh battery, with inverters, charge controllers, etc.) was slightly under the cost of getting power to my plot (10k Euro). Now, of course a sane person would have connected to the grid in any case, however...

Posted by: @editor

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was this primarily an economic decision, a resilience decision or simply geography making the choice for you?

I wanted to be independent of utilities. No monthly bills. The only cost I really have are the property taxes. I have my own water (from a well yes), waste water processing plant, etc. The independence is what I wanted, and while there is of course the up-front cost that comes with that, it's worth it for me. Heating costs me nothing (I get firewood from my own forest) except for some effort. By designing the place to be efficient from the get go, the amount of firewood needed on a yearly basis can be prepared in a few weekends per year, and of course the heat pump brings it down as well.

The waste water processing plant is a two stage anaerobic - aerobic system. This eliminates the need for a large leech field; the water coming out of the system is directly, and legally, discharged into nature (we have strict standards for that here).

Posted by: @editor

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At that latitude, winter solar yield is marginal to negligible I would imagine, so your storage capacity is clearly about buffering seasonal shoulder periods rather than bridging the full winter.

Yes, and to lower the times I need to run the generator to charge the battery. Once or twice a month in winter only. I need about 5kWh per day in winter without making sacrifices for comfort (this includes washer, dryer (heatpump based), dishwasher, etc.). The design take this into account: my dishwasher uses the hot water connection, so it doesn't need to rely on electric to heat the water for example.

Posted by: @editor

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On the generator side, how much bio-diesel are you actually producing per year, and what does winter charging translate to in litres per month? Charging ‘once or twice a month’ suggests your baseline winter electrical demand is relatively disciplined. Are you running the generator purely to charge batteries at high load for efficiency, or also covering direct loads simultaneously? It would be interesting to know the generator size and your typical charge rate into the battery bank.

With the load as mentioned above (5 kWh/day) I need 150kWh per month, for three months where I assume no generation (November, December and January). That means I need to generate 450kWh over winter. My generator gets 3kWh per liter, which means about 150 liter. I tend to make a batch of 200 liter, with whatever is left after winter used to run the tractor (to get wood from the forest, clean snow, etc.). My cost to make the diesel sits around 20 cents per liter, so 30 Euro. 

And yes, the generator is only used to charge the batteries, running at its optimal working point and producing about 10kW output going into the battery. 

Now, I don't have to do this. It's just that it's part of the fun. The feeling of being independent, that the house can be at +25C when it's -40C outside without it costing me anything really, that the wife and kids can take as long and as hot a shower as they want, that I have so much power in summer that I can do things like run a food dehydrator 24/7 to store apples, mushrooms, etc. for winter. That I can process all the firewood needed with electrical tools, run the sauna as much as I want. It's worth the upfront investment for me.

Like I mentioned, I have the entire set-up, with calculations etc. written down here. 

@upnorthandpersonal thank you for sharing details of your home - I thoroughly enjoyed reading your blog posts about your off grid home. Very impressive!