Total home off grid

[Fatterwack]

Yet another newbie! Want to go entirely off grid with my home. Winter drawdown approx 11kWH per day, summer, 5 to 5kWH. I live south France close to Spain so plenty sun all year. I'm on a 240V system. My thoughts: 4 x SOK 4.8kW 48V batteries with server rack; not sure about inverters as I think 2 for my needs plus 1 licensed to feed solar directly into grid. Was looking at GroWatt 5k. Solar panels - advice pls. Will go with monocrystallines; about 5kW total - house aspect is east/west with a south facing wall I can use (3 stories plus grnd flr home so it's a big wall!!).
I will probably import a system from USA as even with tariff it's cheaper/more reliable/better warranties than EU. So, need to grab everything from nuts and bolts to the big stuff!!
Any help much appreciated. ?

 

[DThames]

The subject says "home off grid" but you mention a grid feed license. 240v 50hz?

 

[Fatterwack]

Yep, 240/50 Hertz. I want to isolate the EDF feed and connect the battery storage power to my current AC bus/breaker box - not sure what Americans call it ? ?.

 

[DThames]

Yep, 240/50 Hertz. I want to isolate the EDF feed and connect the battery storage power to my current AC bus/breaker box - not sure what Americans call it ? ?.

LIke this, where the power can go to the grid, from the grid, or from the battery/solar? Hybrid system.

 

[Hedges]

If you have grid power available, using that is probably better than using batteries, or generator, when there is no sun.
Possibly, batteries have come down in price enough to make PV + batteries cheaper than grid power. But only if the batteries do last their claimed cycle life (in one test, only 5% of brands did.)

Do some math on cost of equipment and expected lifespan, determine cost per kWh.

If you can feed into grid, getting a good "net metering" credit, that is likely a better deal than batteries. You can put in a "grid tie" system. In that case, forget buying from U.S. because you need a model configured for your local rules. SMA Sunny Boy is one model, Fronius is another, several others. This can save money compared to just buying from grid. Sometimes break-even as soon as 3 years.

Hybrid or AC coupled battery inverter is an option if you want backup power when grid is down. Nice, but more expensive. You can pay money for the convenience.

 

[Fatterwack]

One reason to go off grid is this: France gov't has just nationalised EDF (elec/gas) because it is over €5 billion in debt. The nuke plants are old and require updating/new plants. In UK, power bills have just jumped by 300/400%. Bills that were approx £1000 per annum are now predicted to increase to £5000 pa. Taxpayers in France will pay for the EDF problems.
I did some math based on Will Prowse prices plus checked with Sig Solar as I was going to buy Sig Solar system. I want to keep the connection with grid in case battery system goes belly up but otherwise, want my electrical independence!! I can earn quite well from feeding into grid which helps defray capital cost of off grid system.
What you guys don't get in US is that we in EU pay substantially more for ECO FLOW, for example, than you do in US. Plus we don't get same warranty protection. We don't have access to the big battery market, so prices are higher. We have Bluetti, but prices far more than you pay. We can buy GroWatt, their prices are more comparable with USA. I guess EU tariffs on China imports are higher than USA.

 

[Ampster]

I have 42kWh of batteries and 10kW of solar in Northern California. The seasonal differences are what make it difficult for me to go off grid. I am a net generator of energy with similar consumption as yours with the exception of two EVs. I do charge the EVs from solar during the day most of the time. I still use the grid as backup and for seasonal differences but my bills are minimal and I have little exposure to energy price increases.

 

[DThames]

One reason to go off grid is this: France gov't has just nationalised EDF (elec/gas) because it is over €5 billion in debt. The nuke plants are old and require updating/new plants. In UK, power bills have just jumped by 300/400%. Bills that were approx £1000 per annum are now predicted to increase to £5000 pa. Taxpayers in France will pay for the EDF problems.
I did some math based on Will Prowse prices plus checked with Sig Solar as I was going to buy Sig Solar system. I want to keep the connection with grid in case battery system goes belly up but otherwise, want my electrical independence!! I can earn quite well from feeding into grid which helps defray capital cost of off grid system.
What you guys don't get in US is that we in EU pay substantially more for ECO FLOW, for example, than you do in US. Plus we don't get same warranty protection. We don't have access to the big battery market, so prices are higher. We have Bluetti, but prices far more than you pay. We can buy GroWatt, their prices are more comparable with USA. I guess EU tariffs on China imports are higher than USA.

if you push power to the grid and then later use from the grid, is that a small cost or a large cost to you? If that cost is small, you can use grid for storage and use a smaller battery system.

 

[Ampster]

If that cost is small, you can use grid for storage and use a smaller battery system.

That is the important question. Seasonal differences are not easily or cost effectively solved by batteries, especially if consumption and generation are inversely correlated.

 

[Hedges]

And so just using PV to reduce consumption may be the way to go. Net metering if available, maybe zero backfeed if A/C required during summer, buy power from grid during seasons and weather when PV doesn't produce.

 

[Fatterwack]

Currently EDF will negotiate 0.20cents per kWH to the grid based on a 20 year contract - which may now change either to increase the price per kWH to relieve grid load or opposite and offer nothing. I think 4 x 4.8kWH SOK batteries is not overkill; it allows for snowy days when solar array efficiency is degraded.
Income from EDF, assuming it continues, pays for my wood pellets each year for heater and range cooker/heater plus WiFi, house and car insurance and a couple bottles of vino!!
I don't believe electric prices in France will stay the same or go down - the opposite. If I buy the system, I'm not a victim of price wars for essential services plus the off grid adds value to resale of my home.

 

[Fatterwack]

That is the important question. Seasonal differences are not easily or cost effectively solved by batteries, especially if consumption and generation are inversely correlated.

Because I live south of France, even in wi ter, we get minimum 5.5 hours. So based my calculations on Will Prowse recommended 5 hours per day per annum, thereforeno seasonal correction required. In summer we get 10 hours sun, so that's basically income.

 

[Fatterwack]

That is the important question. Seasonal differences are not easily or cost effectively solved by batteries, especially if consumption and generation are inversely correlated.

Agree. But usage and generation are always inverse to the seasons!! During summer, I can make money from metering to the grid. Currently, it would pay me 0.20 cents per kWH; I pay 0.15 cents kWH. Since solar income is tax free, it's better to take the income!!! ?

 

[DThames]

Agree. But usage and generation are always inverse to the seasons!! During summer, I can make money from metering to the grid. Currently, it would pay me 0.20 cents per kWH; I pay 0.15 cents kWH. Since solar income is tax free, it's better to take the income!!! ?

I push more to the grid than I use, yearly. I have no battery on my main system. I only pay $23 per month to access the grid, to have a meter. I get credit for what goes to the grid and can use it at the same value. Unless you get more money for pushing at night, you really don't need a battery. (unless for grid down conditions)

 

[Fatterwack]

I push more to the grid than I use, yearly. I have no battery on my main system. I only pay $23 per month to access the grid, to have a meter. I get credit for what goes to the grid and can use it at the same value. Unless you get more money for pushing at night, you really don't need a battery. (unless for grid down conditions)

OK, that's worth looking at whilst EDF is still paying for solar pwr. Thank you.

 

[SveinHa]

A few months ago, I installed a 8.1 kWp off-grid solar system with 12 kWh/48v LiFePO4 batteries (soon to be more than doubled) and 10 kW inverter. When living in Norway at 59 deg N, the sun is quite limited in winter time but whatever sun is available will be used to charge batteries and supply my house. When sun/battery is going low, the grid takes over and supply whatever is needed.

I have limited the available power to my house to about 7.4kW of practical reasons (cabling and fuse) and have a Node Red based home automation system that handels all the unprioritized loads (under floor heating, heatpump, water heater++) so that 7.4kW is more than enough.

My point for choosing this solution over a grid-tie is:

1. The deal with my local power company looks like it is made ONLY for them and almost not for me. I can make better deals with other companys but still not good enough I think.
2. I expect power rationing starting already this winter due to a politically creted power crisis and when the power company cuts power to my house, a grid-tie system also shuts down but my off-grid solution don't care about the grid as long as there are sun and/or battery power available. I also have a diesel generator on site if needed.
3. The last 2 years, the electricity price have 15-doubled and varies quite a bit during each day so I can charge the battery from grid when price is low and use that power when price is high if the sun is insufficient.
4. Generally, the way the world is changing, I feel I need to be more independent form official supply in the widest aspect and this is one important part of the puzzle...

if you push power to the grid and then later use from the grid, is that a small cost or a large cost to you? If that cost is small, you can use grid for storage and use a smaller battery system.

My local energy company pay me a fixed price about €0.1 if I sell surplus power to them and if I store in the grid, they charge me about the same amount for using the grid... so no deal with them for me...

 

[Fatterwack]

A few months ago, I installed a 8.1 kWp off-grid solar system with 12 kWh/48v LiFePO4 batteries (soon to be more than doubled) and 10 kW inverter. When living in Norway at 59 deg N, the sun is quite limited in winter time but whatever sun is available will be used to charge batteries and supply my house. When sun/battery is going low, the grid takes over and supply whatever is needed.

I have limited the available power to my house to about 7.4kW of practical reasons (cabling and fuse) and have a Node Red based home automation system that handels all the unprioritized loads (under floor heating, heatpump, water heater++) so that 7.4kW is more than enough.

My point for choosing this solution over a grid-tie is:

1. The deal with my local power company looks like it is made ONLY for them and almost not for me. I can make better deals with other companys but still not good enough I think.
2. I expect power rationing starting already this winter due to a politically creted power crisis and when the power company cuts power to my house, a grid-tie system also shuts down but my off-grid solution don't care about the grid as long as there are sun and/or battery power available. I also have a diesel generator on site if needed.
3. The last 2 years, the electricity price have 15-doubled and varies quite a bit during each day so I can charge the battery from grid when price is low and use that power when price is high if the sun is insufficient.
4. Generally, the way the world is changing, I feel I need to be more independent form official supply in the widest aspect and this is one important part of the puzzle...

My local energy company pay me a fixed price about €0.1 if I sell surplus power to them and if I store in the grid, they charge me about the same amount for using the grid... so no deal with them for me...

I agree. Putin and GAZPROM cutting supply to EU of 35% of our total source gas usage has hit most EU countries. Being independent of all essential supplies is probably best for many of us this side of the Atlantic. I expect the next 18 months to 2 years will see the price of off-grid systems increase as well. Now's the time to get it done.
Your inverter is only 10kW for 12kWH batteries? I was told to use a multiplier of 1.4 for the peak Watts to size the inverters. Thus, if peak drawdown in Watts is 7kWH, then the inverter should be 10kW. Clearly, I've got something wrong?????

 

[ArtDeco]

If you have grid power available, using that is probably better than using batteries, or generator, when there is no sun.
Possibly, batteries have come down in price enough to make PV + batteries cheaper than grid power. But only if the batteries do last their claimed cycle life (in one test, only 5% of brands did.)

Do some math on cost of equipment and expected lifespan, determine cost per kWh.

If you can feed into grid, getting a good "net metering" credit, that is likely a better deal than batteries. You can put in a "grid tie" system. In that case, forget buying from U.S. because you need a model configured for your local rules. SMA Sunny Boy is one model, Fronius is another, several others. This can save money compared to just buying from grid. Sometimes break-even as soon as 3 years.

Hybrid or AC coupled battery inverter is an option if you want backup power when grid is down. Nice, but more expensive. You can pay money for the convenience.

Gotta ask ... "if the batteries do last their claimed cycle life (in one test, only 5% of brands did.) " ... So which brands were in the 5%?

 

[SveinHa]

Your inverter is only 10kW for 12kWH batteries? I was told to use a multiplier of 1.4 for the peak Watts to size the inverters. Thus, if peak drawdown in Watts is 7kWH, then the inverter should be 10kW. Clearly, I've got something wrong?????

I only need 8kW (or more presice 7.4kW) but the only inverter available at the time was 10kW.

I think maybe the 1.4 multiplier relates to lead-acid batteries, LiFePO4 are able to supply far more current but one should always check specs for all parts of the system. One important wormhole that is easy to step into when selecting solar panels and inverter in cold weather conditions is to add AT LEAST 15% to the specified open circuit voltage and make sure the inverter can handle that voltage.

There is no fixed ratio between inverter and battery capacity but the batteries should be large enough to at least supply your house during the night and for my house that is about 12kWh. Ideally, I would like something like 100kWh but that cost an arm and a leg... I'm planning to add 16 pcs 280Ah EVE cells as soon as I can (they are probably in the Indian ocean right now) and that should give me about 26.5kWh

 

[Fatterwack]

I only need 8kW (or more presice 7.4kW) but the only inverter available at the time was 10kW.

I think maybe the 1.4 multiplier relates to lead-acid batteries, LiFePO4 are able to supply far more current but one should always check specs for all parts of the system. One important wormhole that is easy to step into when selecting solar panels and inverter in cold weather conditions is to add AT LEAST 15% to the specified open circuit voltage and make sure the inverter can handle that voltage.

There is no fixed ratio between inverter and battery capacity but the batteries should be large enough to at least supply your house during the night and for my house that is about 12kWh. Ideally, I would like something like 100kWh but that cost an arm and a leg... I'm planning to add 16 pcs 280Ah EVE cells as soon as I can (they are probably in the Indian ocean right now) and that should give me about 26.5kWh

I think you mean short circuit, not open circuit???