VoltReady Guide
Backup Power Calculator Guide UK | How to Choose the Right Size
UK CALCULATOR GUIDE
The Backup Power Calculator is the quickest way to estimate what size portable power station makes sense for your setup. Instead of guessing, you can work from the devices you want to keep running and build a clearer picture of the battery size and backup level you actually need.
For most UK households, the real question is not just what model looks best, but how much power you need, how long you want backup to last, and whether you are planning for lighter essentials or a stronger all-round setup.
HOW IT WORKS
What the calculator is actually measuring
The calculator helps estimate suitable backup size by combining device wattage, usage time and the amount of battery capacity needed to cover your essentials more realistically.
Device wattage
Start with how much power each device draws. This is usually shown on the device label, power brick or mains adaptor.
Hours of use
The longer you want essentials to stay running, the more battery capacity you need. Runtime planning matters just as much as wattage.
Real-world efficiency
Portable power stations do not convert energy at a perfect 100%, so practical runtime will always be lower than a raw paper calculation.
START HERE
The easiest route for most buyers
Use the calculator first, then move into the right product rather than guessing too early.
Best first step
Sizing help
Use the Calculator first
Backup Power Calculator
The best place to start if you want clearer sizing before you buy
- Estimate likely runtime based on the devices you actually care about
- Helpful for deciding between lighter backup and a stronger all-round setup
- Removes guesswork before you move into the right product page
Best all-rounder
Bluetti AC180P
The strongest recommendation for most UK homes once you know your likely needs
- Better suited to practical home backup than lighter entry-level options
- A strong balance of runtime, portability and all-round everyday flexibility
- The best next step for most buyers after using the calculator
Step-up option
Bluetti AC240P
The stronger choice if your result points to more runtime and more backup margin
- Better for heavier essential loads, longer disruptions and tougher use cases
- A stronger step up if you want more output and more resilience
- Ideal when a lighter or mid-range setup starts to feel too tight
COMMON DEVICE WATTAGE
Typical UK household examples
These ranges are a useful starting point when you are estimating what needs to stay running during an outage.
| Device | Typical range | Why it matters |
|---|---|---|
| Wi-Fi router | 8–12W | Usually the first priority for staying connected during a power cut |
| Smartphone charging | 5–20W | Low draw, but often one of the most important essentials to keep going |
| LED lamp | 5–10W | Useful for simple room lighting without heavy power demand |
| Laptop | 40–65W | Important for home working, communication and productivity during outages |
| Television | 40–90W | Moderate draw that can add up if running alongside several other devices |
| Under-counter fridge | 60–120W | Often the point where buyers realise they need more runtime margin |
| Portable electric heater | 500–2000W+ | Usually not a practical fit for smaller portable backup systems |
RUNTIME FORMULA
The simple way to estimate runtime
Runtime (hours) = Battery Wh × 0.85 ÷ Device Watts
This is a useful guide, not a perfect real-world guarantee. Runtime varies depending on inverter losses, cycling loads, device behaviour and how the power station is being used.
For example, a 10W Wi-Fi router on a 1440Wh unit gives a rough paper estimate of around 122 hours before real-world adjustments. Actual usable runtime is usually lower, which is exactly why the calculator is the better tool for practical planning.
LIGHTER BACKUP OPTION
When a smaller unit may still make sense
Bluetti EB3A
The EB3A is better viewed as the lighter backup option rather than the default recommendation for most households. It can make sense for routers, phones, smaller lights and shorter outages where your calculator result stays modest.
Best fit: lighter essentials, smaller spaces, travel use and buyers who want a compact entry point rather than a stronger all-round unit.
REAL USE CASES
Typical UK backup scenarios
| Use case | Recommended direction | Why |
|---|---|---|
| Wi-Fi and phone charging | EB3A or similar lighter option | Works when your goal is staying connected rather than covering a wider home setup |
| Router, lights and laptop | AC180P | The better all-round recommendation for one-room backup and practical home resilience |
| Fridge, router and lighting | AC240P or modular backup | Usually where buyers benefit from more runtime margin or a stronger system approach |
| Longer or expandable backup planning | AC300 with compatible battery | Better suited to buyers building a more intentional modular setup |
WHY BUY FROM VOLTREADY
A simpler route to choosing the right setup
VoltReady is designed to make backup power easier to understand, with clearer guidance, a more focused product range and practical tools that help you choose faster.
Calculator-led guidance
The goal is to help you size your setup more logically before you buy, rather than pushing you into the wrong product too early.
Clearer product positioning
VoltReady centres the journey around strong, relevant choices instead of burying buyers under too many unclear options.
Help before you buy
If you are still unsure after using the calculator, VoltReady gives you a clearer path into the right product and the right next step.
OUR RECOMMENDATION
Use the calculator first, then start with AC180P for most homes
The calculator is the best first step because it helps turn a vague backup requirement into a clearer size decision. For most UK households, the strongest next product is the AC180P, because it offers the best overall balance of practical backup, flexibility and buying confidence.
When your result points to heavier loads or more runtime margin, step up to the AC240P. For lighter essentials only, the EB3A remains the smaller entry option.
Use the Calculator
View AC180P
RELATED UK GUIDES
Continue your research
Best Portable Power Stations in the UK
Portable Power Station Runtime Guide
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UK Storm and Power Cut Preparedness
Portable Power Station vs Generator
Backup Power Calculator