AI-generated cabin concept, used for illustration.
In this guide
A battery's headline capacity does not by itself tell you how long a cabin will run. Ask for usable capacity and consider the loads, conversion losses and operating limits of the actual system.
Use a simple example as a first check
Suppose a battery system has 4 kWh available for the chosen loads and those loads average 0.5 kW. The ideal arithmetic is 4 ÷ 0.5 = 8 hours.
This is an illustrative calculation with invented inputs. It is not a product runtime promise. Real operation depends on equipment settings, conditions, losses and how the loads change over time.
Your Home: batteries explains considerations in choosing storage. Keep energy capacity distinct from the power the system can deliver at one time.
Ask what the proposal actually supports
Give the designer a critical-load list and the simultaneous-use requirements. Ask which loads are excluded, how reserve settings affect availability and what happens when the available energy is exhausted.
Compare proposals using the same operating scenario. A smaller system described with generous assumptions is not necessarily equivalent to a larger one with a conservative reserve.
Also ask about installation location, service access and maintenance requirements for the actual product. Battery equipment requires appropriate professional design and installation.
Keep the final operating limits beside the load list. That lets you decide whether adding an appliance later fits the plan, instead of discovering during a visit that the original system was sized for a different cabin routine.