Battery Fundamentals — How It Actually Works

The Start-Here Guide · All Markets · Q3 2026 · Internal Use Only

Read this before any market guide. The market guides teach the local rules — this teaches the machine. Every misconception corrected here is one a customer will test you on at a kitchen table.

The One-Paragraph Version

A home battery charges from the customer's solar during the day, stores that energy, and releases it whenever the house needs power and the sun isn't providing it — evenings, nights, cloudy stretches, and outages. One battery does all of those jobs. It is not an emergency-only device that sits idle waiting for a storm: on a normal day it cycles — fills up on midday sun, runs the house through the evening and night, and starts again at sunrise. The money comes from that daily cycle; the outage protection comes along for free.

The Big Misconception — Kill It First

"A backup battery doesn't do self-consumption." False, and this one costs deals. There is no such thing as a backup-only battery versus a savings-only battery in our lineup — it's the same hardware running a priority setting:

• Self-consumption mode (the normal setting): the battery cycles daily — charges from excess solar, discharges to power the house when solar can't. This is where the bill savings live.
• Backup reserve: a slice of the battery (say 20–30%) held back and never used in daily cycling, so there's always something in the tank when the grid fails. The customer picks the number in the app.
• Storm watch / full-backup mode: most systems can automatically fill to 100% and hold when severe weather is forecast, then return to daily cycling after.

So the honest sentence is: "Your battery works for you every single day, and keeps a reserve for the day the grid quits." A rep who pitches the battery as a generator-replacement that sits idle is underselling the product and misexplaining the machine.

The Gas Tank — the Analogy That Explains Everything

Your customer's solar is a gas pump that only runs in daylight. Their battery is the gas tank. The house is the car — it burns fuel around the clock.

• Daytime: the pump runs. Fuel goes first to whatever the car is burning right now; the rest fills the tank.
• The tank has a fixed size. Pump 30 gallons at a 20-gallon tank and 10 gallons overflow — they don't vanish, they spill to the utility at whatever the market pays for exports (in many of our markets, pennies on the dollar).
• Evening and night: the pump is off. The car runs on the tank. If the tank runs dry before sunrise, the car switches to buying fuel from the utility's pump — at their price — until the sun comes back.

That's the entire machine: pump, tank, car. Every battery conversation maps onto it — including the hardest question reps get, which comes next.

A Day in the Life (walk this with customers — it sells)

Morning. Sun comes up, panels start producing. Production first powers whatever the house is using; anything extra charges the battery.

Midday. Panels at full strength, house using little (everyone's at work). Battery fills. Once it's full, extra production exports to the grid — and what that export is worth is the whole reason market rules matter (next section).

Late afternoon into evening. Production fades exactly as the house wakes up — AC recovery, cooking, everyone home, screens on. This is the most expensive time to buy power in most of our markets. Instead of buying it, the house drains the battery.

Night. Panels produce nothing. The battery carries the base loads — fridge, HVAC cycling, chargers — through the night. This is the answer to "how does it power my house at night": the battery IS the nighttime solar. Whether it lasts until sunrise depends on battery size and what the house runs (see Sizing).

If the tank runs dry before sunrise, nothing dramatic happens — the house seamlessly draws from the grid like any normal home, usually at the cheapest hours of the day. Then sunrise, and the cycle restarts.

Why It Saves Money — the Three Levers

The battery saves money by changing when the home uses its own solar power. Which lever applies — and how hard it pulls — is what each market guide tells you. The levers:

Lever 1 — the export gap (self-consumption value). In most of our markets, a kWh the customer exports earns LESS than a kWh they buy costs — sometimes slightly less, sometimes pennies on the dollar. Every kWh the battery stores instead of exporting, then uses instead of buying, captures that gap. Where exports earn wholesale pennies (avoided-cost markets), this lever is huge. Where exports earn near-retail, it's small. The market guide has the number.

Lever 2 — time-of-use arbitrage. Where the utility charges different prices by hour (cheap nights, brutal 2–7 PM peaks), the battery buys nothing during the expensive window — it shifts the home's own midday power into the peak hours. In markets that force solar customers onto time-of-use rates, every solar customer is automatically a battery candidate. The market guide tells you the spread and the honest annual dollars.

Lever 3 — program income. Some utilities and providers pay battery owners — upfront incentives, VPP/demand-response credits — for letting the battery support the grid on peak days. Where these exist they're real money; where they don't, we say so plainly. Never import another market's program.

The honesty rule that governs all three: the battery rarely pays for itself on bill savings alone, and we say that before the customer's calculator does. The purchase is the stack — savings + outage protection + rate protection + system rescue. Each market guide gives you that market's honest stack.

One special case worth understanding: for a customer whose solar already fully offsets their bill under favorable legacy terms (grandfathered 1:1 markets), the battery may save $0 today — and we show that honestly. There the battery is a hedge: it's what keeps their independence when those terms end or change. The market guide tells you if you're in one of these.

"They Have a Battery — Why Do They Still Have a Bill?"

This is the #1 question from the field, and the gas tank answers it. A solar+battery home still buys grid power for one (or more) of four reasons:

1. The tank is too small — overflow by day, empty by night. The most common reason, and the one reps miss. A strong solar day produces, say, 30 kWh of excess while the house is away — into a 13.5 kWh tank. The tank fills by late morning; the remaining ~17 kWh overflows to the grid at the export rate. Then evening comes, the house drains the tank in a few hours, and buys grid power from midnight to sunrise at retail. The customer sold high-value energy for pennies at noon and bought it back at full price at 2 AM — because the tank couldn't hold what the pump delivered. The diagnosis is on their bill: meaningful export credits AND meaningful purchased kWh in the same month = overflow. The honest fix is a bigger tank — a second battery — and that's a legitimate conversation, sized from their actual production and usage, not a reflexive upsell. Show the math from their bill and let the overflow make the case.

2. The car burns more than the pump delivers. If the home uses more total energy than the solar produces, no battery size closes that gap — the battery moves energy across hours, it doesn't create it. That's a solar-sizing conversation (where the market's rules allow it), not a battery conversation.

3. Winter and cloudy stretches. The pump slows down for weeks at a time. The tank helps ride through single cloudy days, but a low-production season means grid purchases no matter the tank size. Normal, expected, and worth saying out loud so nobody's surprised in January.

4. The floor. Fixed charges — customer charges, base fees, minimum bills — survive everything. Even a perfectly-sized system with zero purchased kWh pays the floor. No bill reaches zero, and we say so before the customer notices.

The rep skill: when a battery customer (or a competitor's battery customer) says "I still have a bill," pull the bill and sort the cause into 1–4. Overflow (#1) is a second-battery lead. Consumption gap (#2) is a panel conversation. Season (#3) is expectation-setting. Floor (#4) is honesty. Guessing wrong on which one it is — or worse, having no answer — is how trust dies at the table.

Outages — the Part Everyone Gets Wrong

Solar panels alone do NOT power a home during an outage. When the grid goes down, every grid-tied solar system shuts itself off automatically — a safety requirement called anti-islanding, so panels don't push power into lines workers are repairing. Sunny day, working panels, dead house. Most solar owners have never been told this; telling them is a trust moment.

With a battery, the story flips. The system detects the outage, disconnects the home from the grid in a fraction of a second, and runs the house as its own island: battery powering the loads, and — this is the part that beats every generator — the panels turn back on and recharge the battery each daylight hour. A solar+battery home can ride a multi-day outage indefinitely if the loads are managed and the sun shows up, with no fuel runs, no noise, no cord-pulling in an ice storm.

Reserve math for the conversation: what survives an outage is (reserve % held back) + (whatever daily-cycle charge happens to be in the battery) + (every daylight hour of recharge during the event). Storm-watch mode tops it off before forecast weather. This is why the backup-vs-savings tradeoff is a dial, not a fork: more reserve = more guaranteed outage runway, slightly less daily cycling.

Sizing Basics — kWh, kW, and What Actually Runs

Two numbers define a battery, and confusing them confuses customers:

• kWh (capacity) = how much energy it holds = how long things run. Our batteries hold roughly 10–15 kWh usable. A typical home's overnight base load (fridge, HVAC cycling, lights, chargers) draws maybe 1–2 kWh per hour — so one battery plausibly carries a managed home through a night.
• kW (power) = how much it can deliver at once = what can run simultaneously. Every battery has a limit; try to start the AC, the dryer, and the oven at the same instant and you'll find it.

Backup is usually about the critical loads, not the whole house. The install designates what stays on in an outage — refrigeration, well pump, heat circulation, lights, internet, medical equipment. Whole-home backup exists but takes capacity (often multiple batteries) and honest expectation-setting. The kitchen-table version: "In an outage, this keeps what matters running — not every appliance at once, and we'll design exactly which circuits together."

Climate shapes the pitch: in our southern markets the outage conversation is AC and refrigeration through heat and hurricane season; in the northern ones it's heat circulation and well pumps through ice storms, where a multi-day outage is a frozen-pipes property emergency. Same machine, different hero load.

Common Rep Misconceptions — the Correction Table

Explaining It at the Table — Three Scripts

The gas tank version (for the "how does it work" customer):

"Your solar is a gas pump that only runs in daylight, and your battery is the tank. Right now, everything your panels pump that the house isn't using at that moment spills over to the utility — and they pay you [market's honest framing] for it. The tank catches it instead, and your house runs off the tank all evening and night. And here's the thing about tanks — they're a fixed size. If your panels pump more than the tank holds, the extra still spills. That's why we size this to how your home actually produces and uses power — and why some homes genuinely need two tanks."

The night question (the one you specifically get):

"At night your panels make nothing — that's true with or without a battery. Without one, you buy every nighttime kilowatt from the utility. With one, your house runs on this afternoon's sunshine until the battery's done or the sun's back. Most nights, for most homes, the battery carries it."

The backup-vs-savings question:

"It's not either/or — it's a dial in your app. You tell it 'always keep 25% in the tank for emergencies,' and it works the other 75% every single day lowering your bill. Storm coming? It automatically fills to 100% and waits. One battery, both jobs."

Where the Numbers Come From (bridge to the market guides)

Everything in this guide is the machine. The dollars — the export rate, the peak window, the incentive, the honest annual savings, the floor the bill can't go below — are the market's rules, and they change at every utility line. That's what the market guides are for, and it's why we never quote another territory's numbers: the machine is universal; the money is local. Learn this guide once; learn your market guide cold.