Residential ESSHome energy systems are often described by inverter size alone: 3.6 kW, 5 kW, 6 kW or 10 kW. That number matters, but it answers only one question: how much power the inverter can supply at a given moment. It does not tell you how long the battery will last.
A sound design checks two separate requirements. Power, measured in kilowatts, determines what can run together. Energy, measured in kilowatt-hours, determines how long those appliances can run. A system must satisfy both.
1. List the appliances you want to protect
Start with outage priorities, not every appliance in the building. A typical essential-load list may include LED lights, fans, a television, internet equipment, laptops, a refrigerator and selected sockets. Add air conditioners, water pumps, freezers, microwaves or pressing irons only if they must operate on backup.
Record the quantity and running watts of each appliance. Use the equipment nameplate where available. Online averages are useful for early planning, but the final design should use the actual models installed in the home.
Ten 12 W lights, three 65 W fans, one 120 W television, a 30 W router, one 180 W refrigerator and two 65 W laptops produce a connected running load of about 775 W. In real life, not every selected load will run continuously, but the inverter must still handle credible simultaneous use.
2. Allow for motor and compressor starting surge
Refrigerators, freezers, pumps and conventional air conditioners can draw substantially more power for a short period when their motors start. A design that considers only steady running watts may trip when a compressor starts.
The exact surge comes from the appliance data. For an early estimate, identify the largest motor load and add a suitable starting allowance. The GreenPower calculator does this separately from the running load so the inverter recommendation is not based on energy consumption alone.
Practical rule: inverter capacity must cover credible simultaneous running load plus the most demanding starting event. Battery capacity must cover the energy used over the required hours. One does not replace the other.
3. Add design headroom
An inverter should not be planned to operate at its limit during ordinary use. Headroom allows for measurement differences, load growth and short periods of higher demand. The appropriate margin depends on the load mix, but a preliminary residential calculation often adds 20–30% before matching the result to the next available inverter size.
If the design load is 3.9 kW, selecting a 3.6 kW inverter simply because the numbers look close would be poor practice. The next suitable capacity should be evaluated, together with its phase arrangement and surge capability.
4. Calculate the battery energy requirement
Operating time changes the result quickly. A 1 kW appliance operating for four hours needs roughly 4 kWh of delivered energy, while a 65 W fan running for ten hours needs about 0.65 kWh. The battery must be larger because conversion losses, usable depth of discharge and reserve margin reduce the energy available to appliances.
The GreenPower calculator records hours per day beside every selected appliance. This allows a fan used for ten hours, a 1.5 HP AC used for eight hours and a washing machine used for one hour to contribute different amounts of energy. GreenPower verifies these operating assumptions and the actual appliance ratings before quotation.
5. Size solar generation separately
A battery can provide backup without new solar panels if it charges from the grid or generator. With solar, the array should cover daytime consumption, battery charging and expected weather variation. Roof orientation, shading, cable distance and local irradiation all affect the final number.
Do not assume that a large battery will recharge quickly from a small solar array. The charging window and the energy consumed during daylight must be considered together.
6. Check phase, circuits and installation conditions
Single-phase and three-phase properties require different design decisions. GreenPower also checks the distribution board, earthing, surge protection, changeover logic, cable routes, roof or ground mounting, generator integration and the circuits that will remain protected during an outage.
KSTAR describes its 3.6–6 kW Home Series as a single-phase all-in-one residential system with lithium storage, remote Wi-Fi/app monitoring and quick-connect installation features. Larger or multi-unit residential requirements should be treated as engineered configurations rather than assumed extensions of the single-phase product.
What a useful recommendation should show
- Connected running load and credible simultaneous-use requirement.
- Largest motor or compressor starting allowance.
- Recommended inverter design load with headroom.
- Daily energy calculated from each appliance’s operating hours.
- Battery storage, solar capacity and charging-source assumptions.
- Items that still require an engineering or site check.
Use GreenPower’s load calculator for a preliminary match to the available KSTAR range. The result is a starting point, not a final engineering design or quotation.
Product-reference note: KSTAR Home Series features are based on the manufacturer’s official residential ESS page. Final GreenPower specifications and commercial terms follow the approved design and quotation.