For 3.18 kWh/day you need about 2.7 kWp of panels (6 × 450 W), a 15.4 kWh LiFePO₄ (LFP) bank at 48 V and a 4 kW inverter. The design month is December, when each kWp delivers only 1.76 kWh/day.
Solar array
2.7kWp
6 × 450 W panels at 55°
Battery bank
15.4kWh
300 Ah @ 48 V · usable 11.6 kWh
Battery configuration
4S × 3P
12 × 12.8 V 100 Ah units
Inverter
4kW
continuous; surge ≥ 4.4 kW
Charge controller
80 A
MPPT · 70 A needed at 48 V
Daily load
3.18kWh/day
3.81 kWh/day from the battery bus, incl. inverter losses
Design month
Dec
2.12 kWh/m²/day on panels (sun-hours)
Real autonomy
3days
temperature factor 94%
Months needing backup
0/ 12
none
Summer surplus (unused)
1,666kWh/yr
typical for winter-sized arrays
Battery life
15years
about 68 cycles/yr · rated 6,000 cycles, 15 yr calendar
Rough system cost
€10,937
hardware + install estimate
Monthly energy balance (★ = design month)
| Month | Sun on panels (kWh/m²/day) | Solar (kWh/day) | Need (kWh/day) | Coverage |
|---|---|---|---|---|
| Jan | 2.45 | 5.51 | 3.94 | 140% |
| Feb | 3.39 | 7.48 | 3.94 | 190% |
| Mar | 4.23 | 9.05 | 3.94 | 230% |
| Apr | 4.83 | 10.03 | 3.94 | 255% |
| May | 5 | 10.14 | 3.94 | 258% |
| Jun | 5.02 | 9.99 | 3.94 | 254% |
| Jul | 5.28 | 10.37 | 3.94 | 264% |
| Aug | 5.45 | 10.7 | 3.94 | 272% |
| Sep | 4.88 | 9.87 | 3.94 | 251% |
| Oct | 4 | 8.4 | 3.94 | 214% |
| Nov | 2.57 | 5.63 | 3.94 | 143% |
| Dec | 2.12 | 4.76 | 3.94 | 121% ★ |
Load list
| Load | Wh/day | Share |
|---|---|---|
| Lighting | 320 | 10% |
| Refrigeration | 800 | 25% |
| TV / entertainment | 240 | 8% |
| Computers | 300 | 9% |
| Always-on devices | 240 | 8% |
| Water pump | 750 | 24% |
| Washing machine | 229 | 7% |
| Other | 300 | 9% |
Component checklist
| Component | Specification |
|---|---|
| PV array | 6 × 450 W = 2.7 kWp, 55° tilt, azimuth 180° |
| Battery bank | 12 × 12.8 V 100 Ah (4 in series × 3 parallel) = 15.4 kWh, LiFePO₄ (LFP) |
| Charge controller | MPPT, ≥ 70 A at 48 V (PV string Voc must stay below its max input voltage) |
| Inverter | 4 kW continuous pure-sine, 48 V DC input, surge ≥ 4.4 kW |
| Battery cable & fuse | sized for about 81 A continuous |
- Sun: NASA POWER long-term monthly climate at 44.43, 26.1 (embedded default-site data for pre-rendering), on panels at 55° / 180°, with cell temperature and 12% PV losses.
- Energy chain: AC loads ÷ 92% inverter efficiency + 15 W idle draw → battery bus. 60% of it cycles through the battery at 95% round-trip efficiency; controller efficiency is 97%.
- Days of autonomy cover consecutive cloudy days. NASA monthly means don’t show multi-day storms, so remote critical systems often use 3–5 days and a generator.