What size battery backup do you actually need?
Uses the appliances you set up in the House calculator. Choose how long you need backup for and get the battery capacity (kWh) and inverter rating (watts) that actually covers it. Silent, indoor-safe, no fuel.
Your appliances
7 of 11 House appliances count toward the numbers below.
Battery capacity is limited, so Luxury is excluded by default. 4 selected items also can't realistically run off a battery (pumps, big motors, heavy resistive loads) and are sized out regardless of tier.
How long without power?
Battery size you need
- Continuous
- 1,730 W
- Peak (surge)
- 3,230 W
That's the inverter/output rating a power station needs — anything smaller can't keep up with your load, regardless of battery size.
Battery sizing already excludes the AC/pump loads a soft starter would help — none of your currently selected appliances qualify here.
A soft starter is a small add-on device you install on the motor itself. Don't have one yet? Real options for each load type:
- Micro-Air EasyStart 364 Soft Starter — Home/mini-split AC/RV rooftop AC · ~$340Amazon (affiliate link) →Details →
- SoftStartUSA SoftStartRV — RV rooftop AC · ~$279Amazon (affiliate link) →Details →
- SoftStartUSA SoftStart Well Pump — Well pump/Sump pump · ~$399Amazon (affiliate link) →Details →
To run this load for 4 hours. Assumes your selected watts draw continuously the whole time — real cyclic loads like a fridge compressor draw less on average, so this is a conservative (safe-side) estimate, the same way the generator calculator treats running watts.
Power stations that fit
Prices are typical street prices as of July 2026 — check the current listing before buying.
- 3× combined3× EcoFlow DELTA 3 Ultra~$3,297 total9.22 kWh combined · 3,600 W output per unit · 7,200 W surge per unitAC recharge: 0–100% in about 1.48 hours via AC · 800W max solar in
Combined 9.22 kWh across 3 units clears your 8.3 kWh target, but runs close to empty — consider one more unit or a shorter duration.
EcoFlow's newer answer to the DELTA Pro — similar capacity class, faster recharge, lighter.
- 3× combined3× Bluetti Elite 400~$3,897 total11.52 kWh combined · 2,600 W output per unit · 3,900 W surge per unit
Combined 11.52 kWh across 3 units clears your 8.3 kWh target with room to spare — split appliances between them.
The biggest wheeled unit in this catalog — rolling home backup, not a carry-anywhere station.
- 3× combined3× EcoFlow DELTA Pro~$5,097 total10.8 kWh combined · 3,600 W output per unit · 7,200 W surge per unitAC recharge: 0–100% in about 1.8 hours on 240V, 2.7 hours on 120V
Combined 10.8 kWh across 3 units clears your 8.3 kWh target with room to spare — split appliances between them.
EcoFlow's answer to the Elite 400 — same rolling-home-backup class, faster recharge.
When your selected appliances actually draw across a typical day — and where that lands against what you're looking at buying.
Solid bars are your typicaldraw — each appliance's hours spread across its part of the day. The pale band behind each one is what that hour actually reaches if those appliances happen to run at the same time, which is the number that has to fit. Your worst case peaks around 1,530 W at 10am.
How this calculator works
Battery sizing is a different problem than generator sizing: instead of just covering continuous and peak watts, you also have to cover time— a battery only holds so many watt-hours before it's empty. We total your selected appliances' running watts, multiply by the backup duration you choose, and that's the battery capacity your power station needs.
Once we have that capacity target, we check it against a small catalog of power stations we've actually reviewed and show whichever ones cover both the watt- hours and the continuous/peak watts — smallest first, sized against the buffered figure since that's the number worth shopping for. Nothing here is paid placement; see Disclosure for which brands have an affiliate relationship and how that's labeled. Once you have a target capacity, size the solar array to recharge it based on real sun hours where you live.
One thing battery backup won't solve: hard motor starts. Well pumps, central AC compressors, and similar loads need surge capacity most portable power stations don't have. For those, size a gas or dual-fuel generator instead.
Frequently asked questions
How big a battery do I need for backup power?
Two separate numbers matter. First, continuous and peak watts — the power station's inverter has to cover what your appliances draw, or it can't run them at all. Second, watt-hours (Wh) of capacity — multiply your continuous watts by how many hours you need backup for. A CPAP, router, and a few lights at ~190W for 12 hours needs roughly 2,280Wh (2.3 kWh).
What's the difference between watts and watt-hours?
Watts (W) measure how much power something draws right now — that's what the power station's inverter rating has to beat. Watt-hours (Wh) measure energy over time — that's what the battery's capacity has to beat. A 300W device running for 4 hours uses 1,200Wh, whether it drew that power in one burst or spread evenly.
Can a battery power station run a refrigerator?
Yes for output — a typical fridge draws around 700W running with a brief surge near 2,200W, which most 1,000Wh+ power stations handle fine. The limit is capacity: a 1,000Wh station running just a fridge lasts roughly 12–20 hours depending on duty cycle, so multi-day fridge backup needs either a bigger battery or a way to recharge it, which is a separate question — see the solar calculator.
Battery backup or a gas generator — which do I need?
They solve different problems. Battery power stations are silent, safe indoors, and need no fuel — ideal for electronics, medical devices, and short-to-medium outages. Gas and dual-fuel generators cost far less per watt, refuel in minutes instead of hours, and are the practical choice for high-surge loads like well pumps, central AC, or multi-day whole-house backup. Many households in outage-prone areas end up with both.