Home Battery Backup Guide 2026: Portable vs Installed, What Costs What

"Home battery backup" is two searches wearing one name. The person typing portable battery backup wants to know which $500-$2,000 box keeps the fridge and Wi-Fi alive through tonight's outage. The person typing home battery backup cost is pricing a $12,000-$16,200 installed Powerwall that runs the house and earns money on a time-of-use tariff. This guide prices both lanes with verified numbers only, then gives you the one formula that sizes either one correctly.

Two lanes, two price realities

The split is not quality, it is wiring. A portable power station is a battery you plug appliances into: $549 to $4,799 in verified prices, zero installation, and a hard capacity ceiling measured in watt-hours. An installed home battery is a wall-mounted unit wired behind your meter by a licensed electrician: $11,000-$16,200 in verified examples, automatic switchover, and modular capacity that scales to whole-house loads. They solve different problems, and the worst outcome is paying for one lane and expecting the other's job.

Everything below is split by lane, priced from our verified datasets (solar-generators-2026.json for portables, home-batteries-2026.json for installed), and honest about the cells we leave blank: where a price is not in our verified set, we omit it and say so. No placeholder numbers.

The portable lane: verified prices and $/Wh math

Watt-hours are the currency of this lane, so the only fair price comparison is dollars per watt-hour. The formula, on the record: $/Wh = price ÷ watt-hours. Where a price is verified, we compute it and show it; where it is not, the cell prints a dash.

What portables cannot do

Honest limits, stated qualitatively because they are engineering facts, not prices. Most portable stations are 120V only (the Delta Pro Ultra class with 120/240V is the exception), so 240V appliances are out. None of them will start a central air conditioner; that load belongs to a standby generator or a very large installed battery. And cutover is manual: you plug things in, or you wire a transfer cord. What you get in exchange is silence, indoor safety, and a price that starts at $549. For the full gas-versus-battery decision frame, see Generator vs Power Station vs Solar Generator.

The installed lane: verified examples and the market band

Installed batteries are quoted as projects, so we anchor them two ways: verified example prices where they exist, and the 2026 market band of $700-$1,300 per kWh installed where they do not. Two verified anchors: the Tesla Powerwall 3 at $12,000-$16,200 installed (about $998/kWh, cross-source confirmed 2026-07-14) and the LG RESU 16H Prime at $11,000-$15,000 installed (8MSolar, 2025).

The sizing worksheet: one formula for either lane

Size before you shop; the formula is the same for a $549 portable and a $16,200 installed stack:

kWh needed = daily essential load (kWh/day) × outage days ÷ (depth of discharge × round-trip efficiency)

The two derates are conservative and cited: 0.9 depth of discharge (the LFP norm across these batteries) and 0.9 round-trip efficiency (the Powerwall 3 publishes 89%, Enphase 90%, Franklin 90%). Multiplying them gives 0.81, the fraction of nameplate you can budget against.

Worked example, whole-house-lite: a house that needs 10 kWh per day of essentials through a 2-day outage needs 10 × 2 ÷ (0.9 × 0.9) = 24.7 kWh of nameplate battery. Against that number: one 13.5 kWh Powerwall 3 covers about a day at that load; 2x Powerwall 3 (27 kWh) covers the 2-day target; and a 6,144Wh Delta Pro Ultra class portable covers roughly half a day. Size from your loads, not from these defaults.

Mini example, fridge-and-internet: fridge plus lights plus internet at roughly 2 kWh/day for 2 days needs 2 × 2 ÷ 0.81 = 4.9 kWh. That is still beyond a single 2,048Wh portable for the full 2 days, but a 1,024-2,048Wh class unit covers about a day at that load, and most short outages fall inside that window.

Portable vs installed: the decision table

How solar changes the math

Without solar, a battery is insurance: it sits charged until the grid fails. With solar and a net-metering or time-of-use tariff, the same battery works every day, charging when power is cheap (or free, from your roof) and discharging when it is expensive. That daily arbitrage is why 45% of new home solar installations now attach a battery (SEIA, Q1/Q2 2026): the backup capability has stopped being the only reason to buy. Whether the earnings justify the $700-$1,300/kWh installed band at your rates is exactly what the Battery Storage ROI Analyzer computes, and the generator comparison lives next door in our Whole House Generator Cost Guide.

Battery backup FAQ

The one-sentence version: the portable lane starts at $549 and ends at your fridge; the installed lane starts at $11,000 and ends at your whole house earning money. Size with the formula, then buy the lane that does the job you need done.