What Should Your O‘ahu Battery Keep Powered?

Start a home battery plan with the appliances you want to keep running and how long you need them. The system must support both their combined power demand and the energy they use over time. Keeping a refrigerator, selected lights, and phone chargers running is a different goal from operating air conditioning, cooking appliances, and an EV charger together.

For an O‘ahu household, a useful battery proposal connects those priorities to your actual electrical system, existing solar equipment, and HECO agreement. Start with the loads you care about, then ask the designer to show what the proposed system can support.

Make Three Lists

Write down the appliances and circuits you want to use during an outage, then group them:

• Keep available: The items most important to your household, such as refrigeration, selected lights, and communication devices.
• Use selectively: Equipment you can run briefly or at different times, such as a microwave or washing machine.
• Pause if needed: Large or flexible loads you are willing to leave off, such as EV charging or some air conditioning.

Treat this as a discussion document, not an electrical design. Include the specific appliances, how long you expect to use them, and whether multiple items need to run together. If medical equipment is involved, discuss its continuity requirements with the equipment provider as well as the system designer; a general household backup estimate is not a medical backup plan.

Compare Power and Energy Separately

Two measurements answer different questions:

• Kilowatts (kW) describe power: how much electricity equipment uses or a battery system delivers at a given moment.
• Kilowatt-hours (kWh) describe energy: how much electricity is used or stored over time.

A system needs enough power for the loads running together and enough usable energy for the desired duration. Starting a motor can also require more power than keeping it running, so ask about starting loads as well as continuous demand. The U.S. Department of Energy explains the distinction between storage power and energy capacity in its solar and storage overview.

As a deliberately simplified example, 8 kWh available for household use ÷ a steady 1 kW load = 8 hours. Double that steady load to 2 kW and the same energy lasts 4 hours.

That arithmetic is not a battery performance promise. It assumes a constant load, no charging, and that the stated energy is already available after reserve and losses. Real appliances cycle, the battery may not be full when the outage begins, and equipment limits still apply. Ask for a runtime estimate with assumptions you can inspect.

Clarify What “Whole-Home Backup” Includes

Ask which circuits are connected to backup and which loads must be managed. A proposal described as whole-home backup still needs to explain what can operate at the same time and what happens when demand exceeds the system’s capability.

A selected-load design may fit a household that mainly wants refrigeration, lighting, and communication. A broader design may be appropriate when more circuits need support. Compare the actual circuit plan and operating limits, not the label alone.

Tesla’s outage guidance, for example, explains that combined appliance demand must stay within the installed Powerwall system’s power rating and recommends reducing energy-intensive loads to extend backup. That is product-specific guidance; the installer must verify the limits of the exact equipment proposed for your home. Tesla’s outage guidance

Ask About Reserve and Solar Recharge

Battery settings affect how much stored energy is available when an outage starts. Ask the designer how everyday use and the backup reserve work together, and which settings you will be able to adjust. For Powerwall, Tesla describes the tradeoff between energy reserved for outages and energy available for daily use in its Backup Reserve guidance.

Solar recharge during an outage also depends on the installed system. Ask whether your solar equipment can operate with the battery while disconnected from HECO, what happens when the battery is full or depleted, and what the plan assumes about daytime production. Do not treat the presence of rooftop panels as a guarantee of continued power. Confirm the equipment and control arrangement in writing.

Keep Backup Goals Separate from Program Benefits

For an existing solar home, bring your HECO agreement into the discussion before adding storage or changing equipment. HECO’s Customer Interconnection Tool provides application and amendment paths for existing systems. Your contractor should identify the path appropriate to your agreement and proposed configuration. HECO’s interconnection portal

If a proposal includes a grid-service program, ask how its operating commitments affect your backup priorities. Evaluate any credits or payments separately from the question of which appliances will remain powered. This guide does not assume program enrollment, incentive eligibility, or a particular equipment brand.

Bring These Questions to Your Battery Consultation

• Which circuits will be backed up, and which loads need to be limited?
• What continuous and starting power can this exact configuration support?
• How much usable energy is assumed at the start of the runtime estimate?
• How do reserve settings and everyday battery use affect that estimate?
• Can the existing solar recharge the battery during an outage, and under what conditions?
• What electrical work, equipment changes, and HECO approvals are included?