how-tosavingshome prep

Build a Home Backup System: Calculator for How Many Watts You Actually Need

vviral

2026-01-25

10 min read

Step-by-step backup-power calculator with Jackery and EcoFlow examples — pick the right Wh, compare $/Wh, and know whether to buy on current 2026 sales.

Stop guessing — pick the right home backup size and save hundreds on flash deals

Short outages, pricey impulse buys, or a house-size emergency? If you’re overwhelmed by specs, sales, and scary “will this run my fridge?” questions, this guide walks you through a proven, step-by-step backup-power calculator, real-world examples using the current Jackery HomePower 3600 Plus and the EcoFlow DELTA 3 Max sales (Jan 2026), and clear buy-vs-wait rules so you pick the right capacity for your budget — fast.

Why this matters in 2026

Late 2025 and early 2026 saw more frequent flash sales on portable power stations as inventory stabilized and manufacturers pushed home-ready LFP (lithium iron phosphate) packs. Retailers like those highlighted by Electrek and 9to5toys ran exclusive lows — for example, the Jackery HomePower 3600 Plus at $1,219 (standalone) and $1,689 bundled with a 500W panel, while EcoFlow’s DELTA 3 Max hit a second-best $749 flash price. Those deals are real opportunities — but only if the capacity and inverter specs match your needs.

Quick checklist: What to know before you buy

Watt-hours (Wh): The battery energy available — this determines how long devices run.
Continuous watts: The inverter’s steady output rating (what you can run continuously).
Surge (peak) watts: Short bursts for motor start-ups (fridges, pumps).
Usable capacity: Not all Wh are usable; chemistry and recommended depth of discharge matter.
Inverter efficiency: Expect ~85–95% depending on model and load.
Solar/AC recharge speed: How fast you can refill the battery during an outage.

Step-by-step watt-hour calculator (do this first)

Follow these steps to get a realistic number for the battery capacity you need. We use conservative defaults you can change based on your gear.

Step 1 — List essentials and watt ratings

Find the watt rating on device labels or multiply amps × volts. If you only have voltage and current, use:

Watts = Volts × Amps

Example essentials: router (20W), LED light (10W), laptop (60W), refrigerator average draw (150W), CPAP (60W), well pump (800W surge).

Step 2 — Estimate hours used during outage

Router: 24 hours
Phone/laptop: intermittent — count actual usage (e.g., laptop 2 hours)
Lights: hours used per day (evenings 4–8 hours)
Fridge: use daily Wh estimate (fridge energy use often given in kWh/year — divide)

Step 3 — Total watt-hours needed

Device Wh = Device Watts × Hours. Sum every device for the total Wh required per outage window (e.g., 8 hours or 24 hours).

Step 4 — Adjust for usable capacity and inverter losses

Not all battery Wh are safe to use. Modern LFP systems often let you use 85–90% of the pack safely. Expect inverter efficiency around 85–92% under realistic loads.

Required battery Wh = Total device Wh / (usable_fraction × inverter_efficiency)

Example conservative default: usable_fraction = 0.85, inverter_efficiency = 0.90 → divide by 0.765.

Step 5 — Check continuous & surge watt needs

Sum up continuous watts of devices that will run at the same time and compare to the unit’s continuous rating. Confirm surge capacity for motors and compressors. If your fridge lists 800W startup and 150W running, ensure surge rating ≥800W.

Calculator worked examples

These examples use conservative real-world assumptions — verify every device's label and the power station spec sheet before you buy.

Example A — Nighttime essentials (8-hour outage)

Router: 20W × 8h = 160 Wh
4 LED lights: 40W × 6h = 240 Wh
Laptop: 60W × 2h = 120 Wh
Phone charging: 20 Wh
Refrigerator (assume 150W average over 8h) = 1,200 Wh

Total device Wh = 1,740 Wh. Using the conservative factor 0.765:

Required battery Wh = 1,740 / 0.765 ≈ 2,275 Wh

Recommendation: Pick a unit with >=2,300 Wh usable or a 3,000–3,600 Wh pack if you want headroom and multiple cycles.

Example B — Full day partial-home (24-hour needs)

Fridge: 1,500 Wh/day (typical modern fridge)
CPAP: 60W × 8h = 480 Wh
Lights: 60W × 6h = 360 Wh
Wi‑Fi/phones/laptops: 300 Wh

Total = 2,640 Wh. Adjusted:

Required battery Wh = 2,640 / 0.765 ≈ 3,451 Wh

Recommendation: A 3,500–4,000 Wh unit gives comfortable margin — exactly where the Jackery HomePower 3600 Plus sits by name and spec (check the spec sheet for usable Wh and inverter ratings).

How the Jackery HomePower 3600 Plus and EcoFlow DELTA 3 Max compare in these examples

Price-first facts from current 2026 flash sales: Jackery HomePower 3600 Plus hit an exclusive low of $1,219 (standalone) and $1,689 with a 500W solar panel bundle. EcoFlow’s DELTA 3 Max appeared at a flash price of $749 (second-best recent low). These are strong sale events — but capacity and inverter specs determine value.

Cost-per-Wh: a simple value metric

Cost-per-Wh ≈ sale_price / battery_wh. Use advertised Wh as a baseline but verify usable Wh in the spec.

Jackery example: $1,219 / 3,600 Wh ≈ $0.34 per Wh
EcoFlow example (assumed 2,016 Wh for calculation — confirm model specs): $749 / 2,016 Wh ≈ $0.37 per Wh

Interpretation: Lower $/Wh is better for raw energy storage, but inverter ratings, surge capacity, warranty, and expansion options also matter.

Runtime example: how long will this run a 600W load?

Runtime hours = (battery_wh × usable_fraction × inverter_efficiency) / load_watts

Using Jackery 3,600 Wh with 0.765 combined factor: usable Wh ≈ 2,754 Wh. For a steady 600W load:

Runtime ≈ 2,754 / 600 ≈ 4.6 hours

That shows why using power stations for high-watt short devices (microwaves, hair dryers) gets expensive fast. They’re best for critical small loads and medium loads you need to keep running.

Savings calculator: when does buying on sale beat waiting?

Use this simple rule-of-thumb formula to weigh a current sale vs potential future deals:

Estimate the sale discount: discount% = (usual_price - sale_price) / usual_price.
Estimate probability of equal or better sale in the next 90 days (P). Use knowledge: late 2025–early 2026 had frequent discounts during inventory pushes — P might be ~30–50% for big brands during known sale windows.
Estimate cost of needing one now (stress, food loss, safety) as a monetary or utility value S — if S is high, lean toward buying.

Decision rule: Buy now if sale_discount × (1 - P) + expected immediate_benefit >= 0 (practical simplification: if the deal is >20% and you need it soon, buy; if it's <10% and you can wait, track prices).

Example with real numbers:

Jackery usual price (hypothetical) $1,500 → sale $1,219 → discount = 18.7%
Probability of equal/better sale in 90 days = 30% (P=0.3).
If you rate immediate benefit (avoiding food loss, safety) as $200, compute weighted value: 18.7% × $1,500 × (1 - 0.3) = ~$196.5; plus $200 immediate benefit = $396.5 → clearly buy now.

Translation: if the practical benefit plus expected guaranteed savings is meaningful to you, grab the sale.

Buy vs Wait — practical guidance for 2026

Buy now if: you have an imminent need (frequent outages, medical devices), the sale is ≥15–20% off, or the unit includes solar that meaningfully increases recharge speed.
Wait if: the discount is <10% and you don’t need it immediately. Track price history and set alerts — big model drops often appear around major shopping events or manufacturer restocks.
Consider modular expansion: If you plan to scale (add multiple batteries or integrate a home inverter), prioritize models with expansion ecosystems. For field tests and notes on modular, battery-powered lighting and track systems that explore sustainability and modular power, see Field Review: Modular Battery‑Powered Track Heads for Pop‑Ups.
Warranty and cycle life trump small savings: A cheaper unit with a poorer warranty and lower cycle life can cost far more per usable cycle than a pricier, long-life LFP pack.

Safety and longevity quick tips

Store power stations in cool, dry places — heat reduces cycle life.
Use manufacturer-approved solar panels and cables for guaranteed charging specs. If you rely on solar bundles for faster recharge, consider campsite and portable-lighting reviews that measure panel performance in the field: Field Review: Portable Lighting Kits & Ambient Solutions for Campsites.
Factor in regular maintenance checks (firmware updates, battery health reports if available).
For sensitive loads (CPAP, medical gear), confirm pure sine-wave inverter output and run tests before an emergency.

Real-world case studies — two buyer profiles

Case 1: Suburban family (frequent 6–12 hour outages)

Needs: fridge, wifi, lights, phone charging, small kitchen appliances intermittently. Calculated required battery Wh: ~3,000–4,000 Wh. Jackery HomePower 3600 Plus at $1,219 provided immediate coverage; its lower $/Wh and large capacity make it a solid single-unit solution. If they want faster recharge via solar, the $1,689 bundle with a 500W panel reduces grid draw and extends runtime each day.

Case 2: Apartment dweller (short outages, budget conscious)

Needs: router, laptop, lights, CPAP for single-night outages. Required battery Wh: ~1,500–2,200 Wh. EcoFlow DELTA 3 Max at $749 becomes a cost-effective pick — smaller and easier to store. It’s cheaper per unit and often sufficient for these use cases. If you plan to take a power station on the road, see hands-on comparisons that cover travel and RV/flight suitability: Jackery HomePower 3600 vs EcoFlow DELTA 3 Max: which power station should you bring on an RV or flight trip?

What changed in 2025–2026 — trends that affect your decision

More LFP in consumer units: Longer cycle life and more usable capacity means you can count on 80–90% usable Wh for many modern units.
Retail flash-sale patterns: Brands reduced inflated list prices and leaned on targeted flash deals. That created windows of genuine savings — Jan 2026 had notable manufacturer-driven discounts.
Integration improvements: Newer units offer better solar MPPT charging, faster AC recharge, and smarter app ecosystems for load scheduling.
Policy & incentives: Some local programs expanded storage incentives in 2025; check state/local incentives that might apply in 2026 before purchase.

"If you only buy one thing for emergency prep this year, make it long-life battery capacity with an inverter sized for your highest simultaneous load." — Practical advice for 2026 outages

Final checklist before clicking purchase

Confirm actual usable Wh and inverter continuous & surge ratings on the spec sheet.
Calculate your Wh need using the steps above and add 20–30% headroom.
Compare sale price to typical price and compute $/Wh — then account for warranty and expansion.
If buying on sale, check return policy and extended warranty options. For field-tested portable presentation and seller kits that often pair with small power stations, see Field Review: Portable Seller & Presentation Kits for Installers.
Plan recharge strategy: AC only, solar (panel watts × peak sun hours), or generator hybrid. For portable-event and creator gear with integrated solar and power strategies, check Field Review: Portable Edge Kits & Mobile Creator Gear for Micro‑Events.

Actionable next steps (do this now)

Make a quick device list and run the five-step calculator above (target: get a single number for required battery Wh).
Compare that number to Jackery HomePower 3600 Plus and EcoFlow DELTA 3 Max specs — confirm usable Wh and inverter ratings on the manufacturer pages.
If the Jackery promo ($1,219) or EcoFlow ($749) covers your needs and the discount meets your buy rule, grab it while stock/sale lasts.
If unsure, set price alerts and revisit in 7–14 days — major flash patterns reappear but never guaranteed. If you plan to use the unit for camping or on outdoors trips, compare with ultralight travel strategies in The Evolution of Ultralight Backpacking Kits in 2026.

Closing—Ready now or waiting pays? My quick recommendation

If you have urgent backup needs (medical devices, frequent outages, food storage risk) and the Jackery or EcoFlow sale matches your calculated Wh, buy now — the practical protection and current discount outweigh waiting. If you’re building a future-ready system and want better $/Wh or expansion, map your final capacity target and watch price alerts for a comparable or better deal, focusing on units with LFP chemistry and expansion compatibility.

Want our quick calculator in a downloadable checklist? We’ve turned the step-by-step method from this article into a printable worksheet and price-comparison grid so you can plug in your device list and compare the Jackery and EcoFlow deals side-by-side — claim it below.

Call to action

Don’t overpay or buy the wrong size. Click to download the backup-power calculator worksheet, set deal alerts for the Jackery HomePower 3600 Plus and EcoFlow DELTA 3 Max, and get a tailored buy/wait recommendation based on your exact device list. Act now — flash sales and low-stock promos in early 2026 move fast, and the right capacity will save you money and stress when the lights go out.

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