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House at night, next to a MultiPlus-II inverter/charger and a Victron lithium battery
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Energy balance: battery and panels

List the loads and how long they run. We will calculate daily consumption, required battery capacity and panel power for each month — using PVGIS solar data for 16 voivodeship cities.

16voivodeship cities with PVGIS data
80%LiFePO4 Smart depth of discharge
90%default inverter efficiency
14%system losses in PVGIS data
1Loadspower, hours of operation per day; 230 V — via inverter
Quick add:

The powers and hours in “quick add” are typical values — correct them according to the nameplate and your own usage.

2Battery and inverterhow much energy you can take from the battery and how much it costs to convert it to 230 V
Battery voltage
%
%
for 230 V loads
W
from the inverter datasheet, calculated 24 h/day
3PanelsPVGIS solar irradiation for voivodeship cities
Panel mounting
flat — for example, a campervan roof
Wp
we will show which months they are sufficient for
How we calculate

Assumptions

LiFePO4 Smart2500 cycles at 80% DoD MultiPlus-IImax. efficiency 93–96% Phoenix Inverter SmartECO mode: 0.6–3.2 W SmartSolar MPPTsolar charge controller

Consumption: power × hours × quantity. We divide 230 V loads by inverter efficiency (by default 90% for headroom — datasheets give maximum efficiency, for example MultiPlus-II 93–96%). We calculate the inverter’s no-load consumption over the full day. The value is taken from the inverter datasheet (for example, ECO mode in Inverter Smart limits consumption to 0.6–3.2 W depending on the model).

Battery: capacity (Ah) = daily consumption × days ÷ (voltage × usage). For lead-acid batteries, Victron’s “Energy Unlimited” recommends not discharging below 50%. For LiFePO4 Smart batteries, the manufacturer gives durability at 80% depth of discharge (2500 cycles), and the battery monitor recommends a discharge threshold of 10–20% — hence the default 80%.

Panels: PVGIS data (Joint Research Centre, European Commission), version 5.3, PVGIS-SARAH3 irradiation database from 2005–2023, 1 kWp installation, 14% system losses. For each month, the average daily output is given. The result is the panel power at which an average day in that month will cover consumption — on cloudy days output will be lower, so a battery and a second charging source are needed.

We describe battery and panel selection for a specific system in the guide Campervan installation from scratch.

Sources

Content checked against Victron Energy documentation (datasheets and manuals) — as of 19 September 2026. Report a content error · Revision log