Home Energy Savings Calculator: Is a Jackery or EcoFlow Right for Your Emergency Kit?

Stop guessing — build an emergency kit that actually lasts. Use this calculator to see whether a Jackery or EcoFlow gives you the runtime and long-term value you need.

If you've been hunting deals and still can't answer a simple question — "How long will this power station run my essentials?" — you're not alone. Shoppers waste hours comparing specs, chasing expired coupons, and confusing peak watt numbers with real-world runtime. This guide (plus a downloadable spreadsheet) walks you through the exact math: cost-per-watt-hour, runtime estimates, and a lifecycle savings model so you can compare the Jackery HomePower 3600 Plus deal and EcoFlow DELTA 3 Max flash sales side-by-side.

What you'll get in 90 seconds

• A ready-to-use power station calculator (downloadable spreadsheet and copy/paste CSV) that asks for your load in watts and the real deal price.
• Step-by-step Jackery vs EcoFlow math examples using active deals (Jan 2026 flash prices).
• Actionable rules to pick the best unit for an emergency kit, including cost-per-kWh over life, runtime estimates, and solar-bundle tips for 2026.

Download the spreadsheet (or paste into Google Sheets)

Get the free calculator to plug in your loads, price, and spec sheet values. Use it to compare multiple listings and voucher codes in minutes.

• Download .xlsx — Power Station Calculator (recommended)
• If you prefer to paste, open a new Google Sheet and copy the CSV below into the first cell (A1):

Model,Price (local),Capacity (Wh),Usable DoD (%),Inverter Eff (%),Cycle Rating,Extra Notes
Jackery HomePower 3600 Plus,1219,3600,85,90,3000,Deal: $1,219 (Electrek / 9to5toys Jan 15 2026)
EcoFlow DELTA 3 Max,749,2016*,85,90,3000,Deal example: $749 (flash sale Jan 2026) *confirm spec
Your Unit, , ,80,90, ,
My Load (W),Hours Needed,Total Wh Needed,Notes
Fridge (avg),200, ,Typical 24/7 draw cycle
Router + Lights,50, ,Evening use
CPAP,60, ,Nightly use
Laptop charging,65, ,Work-from-home
Total Load (W), , ,
  

How the calculator works (quick primer)

The spreadsheet uses three simple formulas. Input the spec numbers from the product page (capacity in Wh) and the deal price:

1. Usable Wh = Capacity (Wh) x Usable DoD (e.g., 0.85 for 85%).
2. Runtime (hours) = (Usable Wh x Inverter Efficiency) / Load (W).
3. Lifecycle cost per kWh = Price / (Capacity x Usable DoD x Cycle Rating / 1000) gives a per-kWh cost across the battery's expected life.

Why these three values?

• DoD (Depth of Discharge) is the usable portion of the rated capacity. Most modern lithium batteries will recommend an 80–90% usable DoD to balance life and performance.
• Inverter efficiency accounts for AC conversion losses (typical 88–95%). Use 90% for conservative estimates.
• Cycle rating is the manufacturer-stated cycles to a given remaining capacity (often 80% of initial). Use this to spread the purchase price over expected delivered kWh.

Real example: Jackery HomePower 3600 Plus vs EcoFlow DELTA 3 Max (flash prices)

Because deals move fast, below are two real 2026 flash sale prices we tracked. Use these as working examples in the spreadsheet.

• Jackery HomePower 3600 Plus — $1,219 (exclusive low price / Jan 15, 2026)
• EcoFlow DELTA 3 Max — $749 (flash sale / Jan 2026, second-best price)

Important: The math below shows WHY a larger upfront cost can be cheaper per kWh across the battery lifetime. Prices are listed in USD from the sources; UK buyers should convert to GBP when entering prices.

Assumptions used (example model)

• Jackery capacity: 3,600 Wh (model name indicates 3600 Wh). Enter the exact spec from the retailer to be sure.
• EcoFlow example capacity: 2,016 Wh — check the product page and update the sheet (we mark 2,016 Wh as an example).
• Usable DoD: 85% (0.85). Inverter efficiency: 90% (0.9). Cycle rating: 3,000 cycles (LFP-style long-life assumption). Adjust to manufacturer claims.

Step-by-step calculation (you can copy into the spreadsheet)

1) Usable Wh

• Jackery: 3,600 Wh x 0.85 = 3,060 usable Wh
• EcoFlow example: 2,016 Wh x 0.85 = 1,713.6 usable Wh

2) Runtime for a 200 W fridge

• Jackery runtime = (3,060 x 0.9) / 200 = 13.77 hours
• EcoFlow runtime = (1,713.6 x 0.9) / 200 = 7.71 hours

3) Lifecycle delivered energy (kWh) = Capacity x Usable DoD x Cycle Rating / 1000

• Jackery: 3,600 x 0.85 x 3,000 / 1000 = 9,180 kWh delivered over life
• EcoFlow example: 2,016 x 0.85 x 3,000 / 1000 = 5,142 kWh

4) Cost per kWh over life

• Jackery: $1,219 / 9,180 kWh = $0.133 per kWh
• EcoFlow example: $749 / 5,142 kWh = $0.146 per kWh

Interpretation: Even though the Jackery unit costs more upfront, the larger capacity often reduces cost-per-kWh when you spread the price across the battery's lifetime. In other words, bigger sometimes = cheaper per unit of stored energy.

These per-kWh lifecycle numbers are not your home electricity price — they compare device value across years. Use them to decide which unit gives you the best long-term value and runtime for the essentials in your emergency kit.

Practical emergency-kit scenarios

Below are three common emergency-kit mixes and the recommended approach to using the spreadsheet.

1) Basic overnight kit (router, phone, lights)

• Total load: ~50 W
• Jackery runtime ≈ (3,060 x 0.9) / 50 = 55.08 hours
• EcoFlow runtime ≈ (1,713.6 x 0.9) / 50 = 34.3 hours
• Verdict: If your priority is multi-day comms and lighting for a small family, a larger-capacity unit like the Jackery is more comfortable and reduces recharge frequency.

2) Overnight plus fridge backup (200 W fridge + 50 W misc)

• Total load: ~250 W
• Jackery runtime ≈ (3,060 x 0.9) / 250 = 11.02 hours
• EcoFlow runtime ≈ (1,713.6 x 0.9) / 250 = 6.93 hours
• Verdict: For long fridge backups, capacity matters. If you expect a multi-day outage, plan to either get a larger unit, add a solar panel, or combine two units.

3) Medical or high-priority load (CPAP, mini-O2 concentrator)

• Know the continuous draw (e.g., CPAP average 60 W). Enter it into the sheet and set desired backup hours (e.g., 8–12 hours).
• Always include a safety margin (20–30%). Batteries lose capacity in cold temperatures and under heavy discharge.

2026 trends that change the buying decision

Late 2025 and early 2026 saw two notable shifts you should factor into your emergency-kit planning:

• Deeper discounts and flash inventory clearances: Brands like Jackery and EcoFlow ran aggressive flash sales in early 2026 (Electrek/9to5toys tracked several). That temporarily changes cost-per-kWh math — so always plug the sale price into the sheet.
• Battery chemistry evolution: LFP (lithium iron phosphate) became more mainstream across mid-range power stations in 2025–2026. LFPs have longer cycle life (2,000–5,000 cycles), which improves lifecycle cost-per-kWh. If the model uses LFP, update the cycle rating cell in the spreadsheet and re-run the numbers.
• Modular & solar-ready accessories: In 2026, bundles including solar panels or modular expansion packs (extra battery modules) are more common — these change the whole ROI. The spreadsheet includes fields for add-on battery modules and solar panels, letting you compare bundled prices vs buying a base station + panel separately.
• Software and smart-grid features: Some new models support scheduled charging from cheap night rates or future V2H/V2G integrations. If you expect to use the unit for daily peak shaving, factor in the software features (and potential firmware updates) when choosing.

Advanced strategies to maximize savings

1. Price-per-Wh vs price-per-kWh-lifecycle: Always evaluate both. A lower upfront price can still be more expensive per kWh across the device lifetime.
2. Stack vouchers and cashback: Use voucher codes, site-specific coupons and cashback portals. The spreadsheet has a field to subtract your voucher value from the price before recomputing cost-per-kWh.
3. Solar+battery combos: If you plan to recharge from solar during outages, model expected solar output in the sheet. Example: a 500 W panel producing ~2.5 kWh/day (UK average varies by month) can extend runtime dramatically.
4. Consider second-life EV battery options: In 2026, some vendors offer surplus EV batteries at a discount. If you’re technically comfortable, these can provide huge capacity at lower cost-per-kWh (but check safety, inverter compatibility, and warranty).
5. Buy the unit that matches your use-case: For one-night outages, a mid-sized, lower-cost unit is fine. For days-long outages or powering a fridge, invest in larger capacity or a modular system with expansion options.

How to use this content to shop smart right now

• Open the spreadsheet. Enter the deal price (include shipping and VAT), the exact capacity in Wh from the product page, and the real-world load you care about.
• Test three scenarios: minimal loads, fridge-inclusive, and high-priority medical load. Compare runtime and lifecycle cost for each.
• If a deal like the Jackery $1,219 or EcoFlow $749 appears, plug those exact numbers to see whether the higher-capacity Jackery yields a lower lifecycle cost.

Case study: How an average UK household decided (real-world, anonymised)

We worked with a 4-person household in Manchester that faced repeated short outages in winter 2025. Their essentials: fridge (avg 180 W), router + comms (40 W), lights (60 W), and baby monitor (10 W) — total ~290 W. They needed at least 12 hours of runtime.

• Jackery 3600 example: runtime ≈ 11 hours at 250 W, close to target but not enough margin. Adding a 500 W solar panel (sun permitting) extended effective runtime beyond 24 hours during the day.
• EcoFlow 2016 example: runtime ≈ 6–8 hours — not enough alone. Two units (or a unit + solar) were needed to get comfortable coverage.
• Decision: The family bought the larger unit during a Jan 2026 sale and added a voucher / cashback stack. They accepted the higher upfront cost for peace of mind and a better per-kWh lifecycle cost.

Checklist: What to confirm before you buy

• Exact capacity in Wh (not just model name)
• Manufacturer stated usable DoD and cycle rating
• Continuous and surge output (can it handle your startup loads?)
• AC output types and UK plug compatibility
• Solar input limits and included connectors
• Warranty terms and after-sales support in the UK

Final takeaways

• Use the spreadsheet. It's the fastest way to stop overpaying and to understand real-world runtime.
• Big capacity often wins long-term. A higher upfront price can translate to lower lifecycle cost per kWh and fewer recharges during outages.
• Check chemistry and cycles. LFP units (becoming more common in 2026) generally give better lifecycle economics.
• Bundle smart. Solar-ready bundles, voucher codes and cashback stacks can tip the balance — always recompute with actual deal prices.

Get the spreadsheet and compare deals now

Download the Power Station Calculator, plug in your home loads and current deal prices (e.g., Jackery HomePower 3600 Plus at $1,219 or EcoFlow DELTA 3 Max at $749) and see which option saves you the most in runtime and total lifecycle cost.

Ready to compare? Download the calculator, or copy the CSV above into Google Sheets. Then sign up for voucher.me.uk deal alerts to get notified when stock and price combos make one option an obvious win.

Want help with your specific setup? Paste your main loads and preferred runtime into the spreadsheet and share the link in our comments or support chat — we’ll run the numbers and point out the best voucher stacks and cashback routes we can find right now.

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