List each device → note its power (W) → estimate daily run‑time (hours) → compute Wh = W × hours → convert to kWh (Wh ÷ 1,000) and sum. Add 10–20% for “phantom”/future loads. Example (lean 2‑bed prefab): Look at the last 12 utility bills and note the highest‑use months (kWh). rcurrent, battery temperature, cabinet sYour primary use case should drive capacity decisions, not maximum theoretical needs. Usable capacity differs from total capacity: Lithium batteries provide 90-95% usable capacity while lead-acid only offers 50%. Investing in solar batteries can lead to. Start by entering your average daily energy consumption in kilowatt-hours (kWh). This figure reflects how much energy your household uses per day. Get these right and you will have a battery bank that keeps the lights on through cloudy stretches without. The battery runtime calculator helps you determine how long a battery can power your devices or appliances based on its capacity (Ah), voltage (V), and the power draw of the connected load (W).