Solar unit converter
Converts the units solar planning regularly trips over — with the pitfalls rather than without them: amp-hours to watt-hours only WITH the cell chemistry (LiFePO₄ and NMC differ by 15 % at identical labelling), watts to amps only WITH the voltage, AWG to square millimetres with the note that the geometric formula does not give standard conductor sizes.
The formulas behind the calculator
Every number above can be recomputed: the full calculation path, all assumptions and the data source with retrieval date — plus cross-validation against independent references. Disclosed, not claimed.
An estimate based on the stated assumptions. The final design must be checked by a qualified professional against the rules that apply where you are.
| Step | Formula | Value | Provenance |
|---|---|---|---|
| Amp-hours to watt-hours | Ah * U_nom(chem) * n_blocks | 1,280 Wh | measured |
- Formula
Wh = Ah · U_nominal(chemistry)- Valid for
- Approximation assuming constant voltage.
- Not covered
- Energy content over the real discharge curve, code-referenced AWG areas for stranded conductors.
Frequently asked questions
How many watt-hours are 100 amp-hours?
It depends on the cell chemistry, since Wh = Ah · nominal voltage: 100 Ah is 1,280 Wh for LiFePO4 (12.8 V), 1,200 Wh for lead (12.0 V) and 1,110 Wh for NMC (11.1 V) — a good 15 percent spread behind identical labels. That is why the converter asks for the chemistry and shows the other chemistries' values alongside.
Why does the AWG conversion differ from cable catalogue figures?
The geometric AWG formula does not produce the code-referenced nominal cross-sections used for stranded conductors. The converter therefore outputs both — the geometric value and the nearest commercial size — and explicitly points to the wire-sizing calculator for code-based conductor selection.
How accurate is the amp-hour to watt-hour conversion?
It is an approximation that treats the nominal voltage as constant. The true energy content along the real discharge curve is not represented — a battery's voltage changes as it discharges.
Why does the watts-to-amps conversion need a voltage?
Because watts are power and amps are current — the relation I = P/U only exists with a voltage. 1,200 W at 12 V is a round 100 A (thick cable, big fuse), at 230 V only 5.2 A. That is exactly why system voltage is the first design decision of an off-grid system; the 12/24/48 V calculator works it through.
What does converting insolation to sun hours mean?
It is an identity, not a model: 1 kWh/m² of daily insolation equals exactly 1 peak sun hour, because a PSH is defined as one hour at 1,000 W/m². The converter exists because data sources label the same quantity differently — PVGIS delivers kWh/m²/day, panel calculators ask for PSH. They are the same numbers.
Why is there no kilowatt-to-kilowatt-hour conversion?
Because that is not a conversion but a multiplication by time: kilowatts are power (how fast energy flows), kilowatt-hours are an amount of energy (how much has flowed). A 2 kW appliance uses 6 kWh in three hours. Anyone searching “convert kW to kWh” actually needs an operating duration — that is what the consumption calculator is for, summing appliance powers over their runtimes into daily energy.
How do I convert amp-hours to watt-hours?
Wh = Ah × nominal voltage — and the nominal voltage is the catch, because it depends on the cell chemistry. The same label “100 Ah, 12 V” gives 1,280 Wh for LiFePO₄ (4 cells at 3.2 V), 1,200 Wh for lead and AGM (6 cells at 2.0 V) and 1,110 Wh for an NMC pack (3 cells at 3.7 V). That is a 15.3 % spread at identical labelling. The converter therefore requires the chemistry and shows all values side by side.
How many amps is 1,000 watts?
The question cannot be answered without a voltage — and that is the most common mistake in forums. 1,000 W gives about 83 A at 12 V, 42 A at 24 V, 21 A at 48 V and only 4.3 A at 230 V. The factor between 12 V and 230 V is nearly twenty, and it decides cable size, fusing and terminals. The converter asks for the voltage instead of quietly assuming 12 V.
How many mm² is AWG 10, AWG 6 or AWG 4?
AWG 10 is 5.26 mm², AWG 6 is 13.30 mm² and AWG 4 is 21.15 mm². The converter uses the geometric definition of the American Wire Gauge and matches the published table to within 0.2 %. The accompanying warning matters: these are the circular areas of a solid wire. Stranded conductors have standard nominal sizes from the IEC series (1.5 / 2.5 / 4 / 6 / 10 / 16 mm² …), and for compliant sizing the next commercial size governs, not the computed value.
Are kW and kWh the same thing?
No, and confusing them is the most common category error in solar planning. Kilowatt is a power — what is flowing right now. Kilowatt-hour is an energy — what accumulates over time. A 10 kWp system has 10 kW of peak power and delivers roughly 10,000 kWh a year in Germany; the two numbers happen to be similar in size, which is why they get swapped constantly. Mnemonic: power times time equals energy.
What are peak sun hours and how do I convert them?
Peak sun hours are not a conversion but an identity: they are the irradiation total in kWh/m² per day divided by 1 kW/m². Because the denominator is exactly one, 4.5 kWh/m² a day is exactly 4.5 peak sun hours. The figure says how many hours the sun would have had to shine at standard conditions to deliver the same energy. It has nothing to do with sunshine hours from the weather report, which only count how long the sun was visible.