Hi everyone,

I bought a house a year ago (first floor of 90 m² (970 ft²), second floor not yet done but should be about 60 m² (650 ft²), so about 150 m² (1620 ft²) total) not very far from Paris, France and I want to be 100 % off-grid.

My main problem will be to power a 4-4.5 kW (electrical, 16 kW heat) DIY heat pump during winter (so far less sun available than in summer...). Including everything else I'll need a total of of 16.4 kWh/day (5.5 kWh/day just for the heat pump) on average during the coldest months.

I've been doing some research since a few weeks about the details of what I'll need to meet these goals:

I plan to use 8 Tesla modules in a 48 V configuration (i.e. 4 pairs in // of 2 modules in series) and between 10 and 90 % SoC to extend the cycles life for a total of 33.6 kWh, 30.2 kWh usable with a 90 % efficient inverter, so a bit less than 2 days of autonomy worst case.

I'll make a DIY BMS per module pair based on an Arduino (or maybe a Raspberry Pi, I'll see the pros/cons) to monitor, balance and protect the cells + I'll have full hardware redundancy for the critical protections (over/under voltage, over/under temp, over current) as I'll definitely not rely 100 % on software for that. As it's Li-ion and not LiFePO4 safety will be number one priority everywhere.

As I need to power a big inductive load (albeit with a VFD so soft-start is possible) I was thinking about a LF inverter, a 10 kW one (I should not use more than 8 kW 95 % of the time so 10 kW seems a good size to aim), this one to be exact: https://www.ebay.fr/itm/10000W-LF-P...C-48V-to-AC-230V-Charger-UPS-LCD/113493808631

As I'm in a region with a big solar difference between summer and winter I'll need to over-panel like crazy to meet the demand in winter. I'm thinking of minimum 52 panels of 315 W (that's 89 m² and i'm not even sure the roof is big enough... I need to do the calculations about that) for a total of 16.4 kW.

I have a 4-sided roof with the smaller side facing SW and a bigger one facing SE and about 45° of inclination for both (so at least better for winter than summer, good news about that).

Edit: thanks to @nosys70 who catched a big mistake I change the number to double that; so 33 kW of panels.

See question 3.

1. Is the battery size enough for my needs? I'd like to put more but my budget is tight so...

2. Does anyone know if the inverter is ok quality-wise?

3. I'm debating using the MPP PIP 5048 series as it includes both the inverter and SCC but I'll need at least 3 of them to handle the solar power and I'm not sure about the AC quality and surge capability, especially when paralleled; do you have any input on that?

4. Do I need more panels? less panels?

I'm open to any other advice you have to offer (I can provide more data and calculations details if needed), and thanks for reading this long post

I bought a house a year ago (first floor of 90 m² (970 ft²), second floor not yet done but should be about 60 m² (650 ft²), so about 150 m² (1620 ft²) total) not very far from Paris, France and I want to be 100 % off-grid.

My main problem will be to power a 4-4.5 kW (electrical, 16 kW heat) DIY heat pump during winter (so far less sun available than in summer...). Including everything else I'll need a total of of 16.4 kWh/day (5.5 kWh/day just for the heat pump) on average during the coldest months.

I've been doing some research since a few weeks about the details of what I'll need to meet these goals:

**Battery**I plan to use 8 Tesla modules in a 48 V configuration (i.e. 4 pairs in // of 2 modules in series) and between 10 and 90 % SoC to extend the cycles life for a total of 33.6 kWh, 30.2 kWh usable with a 90 % efficient inverter, so a bit less than 2 days of autonomy worst case.

I'll make a DIY BMS per module pair based on an Arduino (or maybe a Raspberry Pi, I'll see the pros/cons) to monitor, balance and protect the cells + I'll have full hardware redundancy for the critical protections (over/under voltage, over/under temp, over current) as I'll definitely not rely 100 % on software for that. As it's Li-ion and not LiFePO4 safety will be number one priority everywhere.

**Inverter**As I need to power a big inductive load (albeit with a VFD so soft-start is possible) I was thinking about a LF inverter, a 10 kW one (I should not use more than 8 kW 95 % of the time so 10 kW seems a good size to aim), this one to be exact: https://www.ebay.fr/itm/10000W-LF-P...C-48V-to-AC-230V-Charger-UPS-LCD/113493808631

**PV panels**As I'm in a region with a big solar difference between summer and winter I'll need to over-panel like crazy to meet the demand in winter. I'm thinking of minimum 52 panels of 315 W (that's 89 m² and i'm not even sure the roof is big enough... I need to do the calculations about that) for a total of 16.4 kW.

I have a 4-sided roof with the smaller side facing SW and a bigger one facing SE and about 45° of inclination for both (so at least better for winter than summer, good news about that).

Edit: thanks to @nosys70 who catched a big mistake I change the number to double that; so 33 kW of panels.

**SCC**See question 3.

**Questions**1. Is the battery size enough for my needs? I'd like to put more but my budget is tight so...

2. Does anyone know if the inverter is ok quality-wise?

3. I'm debating using the MPP PIP 5048 series as it includes both the inverter and SCC but I'll need at least 3 of them to handle the solar power and I'm not sure about the AC quality and surge capability, especially when paralleled; do you have any input on that?

4. Do I need more panels? less panels?

I'm open to any other advice you have to offer (I can provide more data and calculations details if needed), and thanks for reading this long post

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