Solar Backup Power Calculator for Home Emergencies

Quick Answer

Home emergency backup covering a fridge, lights, sump pump, CPAP, and router uses 4.9 kWh/day, requiring 1800W of solar and a 500Ah battery for 3-day autonomy. The EcoFlow Delta 2 Max is the recommended system for serious home backup. With a 400W solar panel, it recharges during the day and covers critical loads through any extended outage.

Pre-Calculated System Specs

Based on 4.5 peak sun hours, 3-day autonomy, and typical Emergency Backup loads.

ComponentMinimum SizeNotes
Daily Load4.9 kWhRaw before system losses
Adjusted Load5.9 kWh+20% system loss buffer
Solar Panels1800W9x 200W or 5x 400W panels
Battery500Ah at 48VLiFePO4, 3-day autonomy (22.0 kWh total)
Charge Controller50A MPPTNEC 1.25x safety factor applied
Inverter1000W continuous2500W surge capacity, pure sine wave

Want to adjust for your exact appliances? Customize these numbers with our solar calculator

Recommended Turnkey Solution

EcoFlow Delta 2 Max

2,048Wh expandable to 6,144Wh, 2,400W AC output — the cabin and tiny home standard.

2,048Wh

Capacity

2,400W

AC Output

1000W

Max Solar In

Buy on EcoFlow.comView Solar Bundle

DIY Component Approach

Prefer to build a custom system? Use these components matched to the calculated specs above. A DIY build typically costs 20-35% less than a turnkey power station for the same energy capacity.

Solar Panels

1800W total (9x 200W panels recommended)

Renogy 200W 12V Monocrystalline on Amazon

Battery

500Ah at 48V LiFePO4

LiTime 12V 200Ah LiFePO4 on Amazon

Charge Controller

50A MPPT minimum

Renogy 40A MPPT Rover on Amazon

Inverter

1000W pure sine wave

Renogy 2000W Pure Sine Wave Inverter on Amazon

Emergency Backup Solar System Guide

Emergency home backup power has shifted from generators to battery-solar systems for several reasons: no fuel to store, silent operation, and instant-on response. A generator takes 30–60 seconds to start; a power station like the EcoFlow Delta Pro switches to battery power in under 30 milliseconds — fast enough to keep sensitive electronics like CPAP machines and network equipment running without interruption. For planned outages (scheduled utility maintenance) versus unexpected outages (storms), battery backup responds better.

The critical design question for emergency backup is: what loads are truly critical? Most homeowners discover that their actual minimum requirements are a fridge, a few lights, phone charging, and possibly a sump pump or medical device. These critical loads sum to 3,000–5,000Wh per day — well within the range of a single EcoFlow Delta Pro or a 200Ah LiFePO4 battery bank. Heating, cooling, and cooking are almost always handled separately with propane during a prolonged outage.

Solar recharge transforms a finite battery backup into an indefinite backup system. A 400W solar array charges a depleted 3,600Wh Delta Pro in about 10–12 hours of good sun — meaning the system regenerates overnight and every daylight period during an extended outage. This is the critical difference between emergency backup and a traditional generator: a generator requires fuel delivery; a solar-backed system refuels itself as long as the sun rises.

Frequently Asked Questions

What size solar battery backup do I need for a home power outage?▼
Critical home backup loads — fridge, lights, phone charging, router, CPAP, and sump pump — use about 4,500–6,000Wh per day. For a 3-day outage buffer, you need 13,500–18,000Wh of battery storage. The EcoFlow Delta Pro (3,600Wh) with two Smart Extra Batteries (7,200Wh added) gives 10,800Wh total — enough for 2 full days of critical loads. Pairing with a 400W solar panel extends runtime indefinitely during daylight. For complete 3-day autonomy without solar, you need three Delta Pro units.
How much does a whole-home solar backup cost?▼
A portable power station backup (no installation) using EcoFlow Delta Pro costs $3,500–5,000 for a 3,600–7,200Wh system. Add 400W of solar panels for $300–500. A permanently installed whole-home backup with a Powerwall or SolarEdge system runs $10,000–20,000 installed. The middle ground — a large portable power station plus wall outlets — provides the best cost-performance for most homeowners. The EcoFlow Smart Home Panel ($500) integrates Delta Pro directly with your home's circuit breaker panel.
Can solar run a well pump during a power outage?▼
Yes, with the right system. A 1HP well pump requires a 2,500W surge-capable inverter and a 100Ah+ LiFePO4 battery bank at 24V. The EcoFlow Delta 2 Max (2,400W AC output) handles a 3/4HP pump but may struggle with 1HP motors on startup. The EcoFlow Delta Pro (3,600W) handles 1HP well pumps reliably. Add a 220W solar panel to recharge between pump cycles. For a dedicated backup well pump system, an off-grid solar controller and DC submersible pump (Grundfos or Shurflo) eliminates the inverter requirement entirely.

Need a custom calculation?

The numbers above use typical emergency backup defaults. Adjust for your exact appliances and location.

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