Generator and Battery Hybrid Estimator

The battery carries the house first. Its hours alone are the battery energy, less the reserve, divided by the average load. When it reaches the reserve, the generator starts, carries the house and recharges the battery at the battery's charge rate, or at whatever the generator has left over after the load, whichever is lower. If nothing is left over, the generator cannot carry the house and charge the battery at once, and the estimate says so.

The recharge time is the energy to put back divided by that charge rate. One cycle is the battery's hours plus the recharge hours, and the generator's hours a day are its share of each cycle over 24 hours. While it runs, its loading is the house load plus the charging, as a share of its rating. With the fuel figures entered, the fuel use comes from the generator fuel estimator's arithmetic at that loading for those hours.

The model assumes a steady load, and a controller that starts the generator when the battery reaches its reserve and stops it once the battery is recharged. Real loads rise and fall, and every system's controls differ, so the figures are a starting point. A licensed electrician's load assessment on site decides how a battery and a generator are sized and wired to work together.