Batteries 101.

kW vs. kWh — the whole subject in one distinction

Kilowatt-hours (kWh) are how much energy a battery holds — the size of the tank. Kilowatts (kW) are how fast it can deliver that energy — the size of the pipe. A battery can have a big tank and a small pipe (runs a long time but can't start the AC compressor) or the reverse.

Almost every disappointment we hear about batteries traces back to one of those two numbers being wrong for the job. Ask for both. Ask for the continuous kW rating and the peak (surge) rating separately — motors like AC compressors and well pumps need a surge to start.

Whole-home vs. essential loads

Essential-loads backup moves a handful of circuits — refrigerator, some lights and outlets, Wi-Fi, maybe a mini-split — onto a protected sub-panel. It's cheaper and a single battery usually covers it for a day or more.

Whole-home backup backs up the main panel so life continues more or less normally, including central AC. It takes more kW (to start the compressor) and more kWh (AC is the biggest load in a Florida house), which usually means multiple battery units, and sometimes a smart panel or load controller that sheds the biggest loads automatically when the battery gets low.

Neither is "right." The question is what you actually need to keep running, for how long, and what that's worth to you.

Backup vs. daily cycling

A backup-only battery sits full and waits for an outage. A daily-cycling battery charges from solar during the day and discharges in the evening to reduce what you buy from the utility. Whether daily cycling pays depends heavily on your utility's rate structure and net-metering rules; on some Florida tariffs it does little for the bill, on others (especially commercial demand tariffs) it does a lot. This is one of the first things we check with your actual bill.

What actually happens when the grid goes down

Grid-tied solar without a battery shuts off during an outage — by code, to protect line workers. Solar with a battery and the right transfer equipment forms its own small grid: the battery powers the house, and the panels recharge the battery during the day. In a multi-day storm outage, that daytime recharge is what turns "a night of backup" into "as long as the sun comes out."

Two practical notes for Florida: batteries should be installed above the base flood elevation your permit requires, and a system that's monitored is a system you'll know is working before the storm, not after.

Battery vs. generator

Generators are cheaper per kW and run as long as you have fuel. They're also loud, need maintenance and fuel logistics during exactly the week fuel is hard to get, and do nothing for your bill the other 360 days a year. Batteries are silent, automatic, maintenance-light, and can earn their keep every day. Some properties sensibly have both: battery for the first day or two and daily savings, generator as a long-outage backstop.

Systems you'll hear about

Most residential and small-commercial storage in Florida comes from a short list of manufacturers, each with a different design philosophy. Specifications change with each product generation, so we've listed how to think about them rather than numbers that go stale:

Seven questions to ask anyone selling you a battery

• What is the usable kWh (not nameplate) and the continuous and peak kW?
• Which loads are backed up, and how long will they run at a realistic draw?
• Will my central AC start on battery? Show me the surge math.
• How does it recharge during a multi-day outage?
• What is the warranty in years and in throughput or cycles?
• Where will it be mounted relative to flood elevation and setbacks?
• Who holds the contractor license on this installation, and what is the number?