Power Station Runtime
Pick your appliances · set when each starts and how long it runs · see if your battery can cover it
Power Station Runtime Calculator: Sizing Battery Backup for Kenya
Kenya's electricity grid is improving but still delivers regular outages, 2-8 hours per week in most urban areas, longer in rural and informal settlements. Power stations (portable lithium-ion battery systems like EcoFlow, Jackery, Bluetti) have become the go-to solution for keeping essentials running during blackouts, powering Starlink/WiFi for remote work, or charging the household during extended outages.
But buying the right size is harder than marketing suggests. Watt specs are confusing, "expandable capacity" claims are often misleading, and nobody tells you that running a 2000W kettle on a 1800W station doesn't work. This guide explains the math and helps you right-size.
The two numbers that matter: rated output vs stored energy
Every power station has two key specs, and most people confuse them:
Rated Output (watts, W)
The maximum instantaneous power the inverter can deliver. If you plug in devices that collectively draw more than this, the station shuts down to protect itself.
Example: A station rated 1500W continuous / 2500W surge. You can run 1499W of load all day. You can briefly start a 2400W microwave (appliances often surge on startup). But 1700W continuous will trip the overload.
Stored Energy (kilowatt-hours, kWh)
The total battery capacity, how much energy the battery holds. This determines how long you can run. A 1 kWh battery can deliver 1 kW (1000W) for 1 hour, or 500W for 2 hours, or 100W for 10 hours.
Popular models:
| Model | Rated Output | Stored Energy | Price Range |
|---|---|---|---|
| EcoFlow River 2 | 300W continuous / 600W surge | 256 Wh | KES 30,000-35,000 |
| Jackery Explorer 500 | 500W / 1000W surge | 518 Wh | KES 50,000-60,000 |
| EcoFlow River 2 Pro | 800W / 1600W surge | 768 Wh | KES 75,000-85,000 |
| EcoFlow Delta 2 | 1800W / 2700W surge | 1024 Wh | KES 130,000-150,000 |
| Bluetti AC200P | 2000W / 4800W surge | 2000 Wh | KES 180,000-220,000 |
| EcoFlow Delta Pro | 3600W / 7200W surge | 3600 Wh | KES 350,000-400,000 |
Runtime formula
Runtime (hours) = Battery (Wh) ÷ Total Load (W)
= Battery (kWh) ÷ Total Load (kW) × 1000
Examples:
- 1024 Wh Delta 2 + 200W load = 5.1 hours
- 1024 Wh Delta 2 + 1500W load = 0.68 hours (41 minutes)
- 2000 Wh Bluetti + 150W load = 13.3 hours
Note: Real-world runtime is typically 85-95% of theoretical because inverter conversion loses some energy as heat. Our calculator assumes ideal conditions, mentally haircut results by 10% for realistic planning.
How to use the calculator
Step 1, Set station capacity
Enter both the rated output (W) and stored energy (kWh). Use quick presets (500W/0.5kWh, 1kW/1kWh, 2kW/2kWh, 5kW/5kWh, 10kW/10kWh) to match common models or set custom values for specific units.
Step 2, Pick appliances
33 pre-configured appliances with Kenyan-typical wattages. Organized by commonality: WiFi, lights, phone charging, TV, refrigerator first; then kitchen, laundry, comfort, work, utilities; heavy loads (water heater, oven) last.
Click + to add units (e.g., 8 LED bulbs). Click − to remove.
Step 3, Set duration per appliance
Each appliance has a duration selector: Full time (24h continuous), 12/8/6/4/3/2/1 hours, 30/15/10/5 minutes. Sensible defaults per appliance:
- WiFi, Fridge, Freezer, CCTV, Full time (always on)
- LED lights, 6 hours (evening use)
- Phone/laptop charging, 3 hours
- TV, fans, desktop, 4 hours
- Kettle, toaster, blender, 5 minutes
- Iron, water pump, 30 minutes
- Water heater, microwave, 10-15 minutes
Step 4, Read the results
Four stat cards at top:
- Estimated Runtime, hours the battery sustains peak draw
- Peak Load, simultaneous watts (critical vs your inverter rating)
- Battery Used, % of kWh capacity consumed by your planned usage
- Energy Used, total kWh consumed across the session
If peak load exceeds rated output → red Overload alert. If energy used exceeds battery → Exceeds one charge alert.
Typical Kenyan household wattages (verified)
Don't trust manufacturer labels alone, use these researched Kenya-typical values:
| Appliance | Typical Wattage | Notes |
|---|---|---|
| LED bulb | 8-12W each | 8 bulbs ≈ 80W total |
| WiFi router | 10-15W | Always-on |
| Phone charger | 10-25W | Fast chargers higher |
| Laptop (in use) | 45-90W | Gaming laptops to 200W |
| TV 32-43" | 75-120W | LED panels |
| TV 50-55" | 150-200W | |
| TV 65"+ | 200-350W | OLED higher |
| Refrigerator | 100-200W continuous | 600-1200W startup surge! |
| Deep freezer | 150-300W continuous | Bigger surge |
| Microwave | 1000-1500W | Only on when cooking |
| Electric kettle | 1500-2200W | Only 3-5 min per boil |
| Electric iron | 1000-1800W | Cycles on/off |
| Hair dryer | 1500-2000W | Short duration |
| Air conditioner 1 HP | 750W | Inverter ACs lower |
| Air conditioner 1.5 HP | 1100W | |
| Washing machine | 400-600W (heating ON: 1800W) | Varies by cycle |
| Water pump | 500-1100W | Depends on head |
| Electric stove (1 plate) | 1500W | Per plate |
| Electric stove (double) | 2000W | |
| Instant water heater | 3000-4500W | High load, short runs |
Realistic sizing by use case
Power outage essentials (4-8 hour blackout)
Just want to keep WiFi + lights + phone charging + maybe TV running:
- Load: ~200-300W continuous
- Runtime target: 6 hours
- Needed: ~1.5-2 kWh battery, 500W+ rated output
- Recommended: EcoFlow River 2 Pro (0.8 kWh, 800W) for short outages; Delta 2 (1 kWh, 1800W) for longer
Whole-day outage including fridge (12-24 hrs)
- Load: ~150W average (fridge cycles), peaks when other devices on
- Runtime target: 24 hours
- Needed: ~4-6 kWh battery, 2000W rated output
- Recommended: Bluetti AC200P + expansion battery, or Delta Pro
Remote work setup (Starlink + laptop)
- Load: Starlink 75W + laptop 80W + monitor 30W = ~185W
- Runtime target: 8-hour workday
- Needed: 1.5-2 kWh battery, 500W rated
- Recommended: Delta 2 (1 kWh) for occasional use; Delta 2 Max (2 kWh) for daily work
Entire home for 12+ hours
- Load: 500-1500W varying (lights, WiFi, TV, fans, occasional appliances)
- Runtime target: 12-24 hours
- Needed: 8-15 kWh battery, 3000W+ rated
- Recommended: Delta Pro (3.6 kWh) + expansion batteries, or a proper solar-battery system
Solar integration: battery as part of a larger system
Power stations are just batteries with clever inverters. If your outages are frequent or long, pair with solar panels to recharge during the day:
- 200-400W solar panel (portable), recharges most stations in 3-5 hours of sun
- Fixed rooftop 1-3kW array, can run critical loads + charge station during outages
- Full solar+battery home system, 5-10kWh of LiFePO4 storage + 5-10kW inverter + 4-8kW panels, covers full household needs, KES 800K-1.5M installed
For casual outage coverage, a station alone is fine. For frequent long outages or off-grid living, step up to a full solar-inverter-battery home system (different from portable stations).
Common mistakes when sizing
- Ignoring surge watts. A fridge draws 150W continuous but surges 800-1200W when the compressor starts. If your station's surge rating is below this, fridge won't start even if "150W" fits within your continuous rating.
- Overestimating LiFePO4 lifespan. Most cells are rated for 3,000-6,000 cycles. Daily deep-cycling means 8-16 years of useful life. If you only use the station a few times a month, 20+ years.
- Trusting manufacturer "expandable capacity" claims. Yes, you can often daisy-chain batteries. But each expansion is another KES 50-100K. Check the total system cost vs buying bigger upfront.
- Buying for worst-case instead of typical. You don't need 10kWh if typical outages are 4 hours. Buy for your 80th-percentile outage and accept discomfort in the 20% long ones.
- Running high-wattage appliances (kettle, iron) without checking. A 1200W station can't run a 2000W kettle, period. Either boil off-station or step up to a bigger unit.
Charging options
Every station can be charged from multiple sources:
- AC wall (mains), fastest, typically 600-1800W input. Charges Delta 2 in ~1 hour.
- Solar panels, slower but free energy. Check MPPT range (typically 10-150V input).
- Car 12V, slow (~100W), emergency use only
- Generator, if you have one, provides grid-independent fallback
For frequent users: have two charging paths (AC + solar). When the grid is down, solar keeps you going.
Related calculators
- Smart Budget Planner, plan the budget for a power station purchase
- Loan Calculator, if financing a large solar system, model the EMI
- Passive Income Calculator, consider reliability-as-productivity (uninterrupted work = income)
Kenya's electricity situation will improve over the next decade, but outages won't disappear. A right-sized power station is a worthwhile purchase for most urban households, buy too small and you'll regret it in the first long outage; buy too big and you've wasted capital. Use this calculator to get the right size for your actual usage patterns.
Frequently Asked Questions
How long will my power station last?
Simple formula: Runtime (hours) = Battery capacity (kWh) ÷ Total load (kW). A 1 kWh battery powering 500W of devices lasts 2 hours. Our calculator does this math for you accounting for appliance usage durations and peak-load overload checks.
What's the difference between rated output and stored energy?
Two different specs often confused: Rated Output (W) is the maximum instantaneous power the inverter can deliver, don't exceed it or you get an overload shutdown. Stored Energy (kWh) is total battery capacity, this determines how long you can run. A 3000W / 1.5kWh station can power a microwave (1200W) for max 75 minutes.
Can my power station run a fridge?
Yes, most can. Modern fridges draw 100-200W continuously with brief startup surges of 600-1200W. A station rated 1000W+ continuous with a 1200W surge tolerance works. Budget 1-2 kWh to run a fridge for 8-12 hours.
What happens if I exceed the station's output rating?
The inverter shuts down immediately to protect itself and the battery. Everything loses power until you reduce load. The calculator warns you with a red "Overload" alert so you can prevent this before it happens.
Are the runtime estimates accurate for real-world use?
Typically accurate within 10-15%. Real-world runtime varies due to: battery age (10-20% capacity loss after 3 years), temperature (cold reduces output), inverter efficiency (~85-95%), and appliance duty cycles (fridges cycle on/off). We don't model these, figures are "ideal" estimates.
What wattage do common Kenyan home appliances use?
Typical: LED bulb 8-12W · Laptop 45-90W · Phone charger 10-25W · WiFi router 10-15W · TV 100-250W · Fridge 100-250W · Microwave 1000-1500W · Electric kettle 1500-2200W · Iron 1000-1800W. All 33 appliances in the calculator use researched Kenya-typical wattages.
What size power station do I need for outages?
For a 4-hour blackout covering essentials (WiFi, lights, phone/laptop charging, TV): 0.5-1 kWh is enough. For 24-hour outages including a fridge: 2-3 kWh. For whole-day operation with AC: 5-10 kWh. The calculator lets you pick appliances and see which size fits.