Backup Power guide
Power Station Runtime Calculator for a Winter Outage: Furnace Blower, Sump Pump and CPAP
Quick answer
- A CPAP is the easy one. ResMed lists the AirSense 11's typical power use as 56.1 W.[7] Eight hours a night is about 450 Wh, so a 768 Wh station covers about 1.5 nights and a 2,048 Wh station about 3.9 nights at an 85% usable share.[1][2][4]
- A sump pump depends on how often it runs. Champion's chart puts a 1/3 hp pump at 500 to 800 running watts and 1,000 to 1,600 starting watts.[5] Check the station's surge rating before anything else.
- A furnace blower uses the most energy. Champion lists 300 to 800 running watts for a 1/2 hp furnace fan.[5] Running a third of each hour at 800 W uses about 6,400 Wh a day, more than three times what a 2,048 Wh station holds.
- Cold matters. EcoFlow's River 2 Pro won't charge below 32°F.[1] Keep the station somewhere heated.
A hardwired furnace or sump pump can't plug into a power station; connecting either needs a transfer switch or interlock installed by a licensed electrician (see our interlock vs. transfer switch guide).
Winter outage runtime calculator
| Item | Running W | Starting W | How long it runs |
|---|---|---|---|
| min/hour | |||
| min/hour | |||
| h/night |
Where the figures come from
- Wattage: Champion's generator wattage chart gives ranges for each appliance.[5] Honda's guide gives single figures that are higher for some items: 875 running and 2,350 starting watts for a 1/2 hp furnace fan, and 800 running and 1,300 starting watts for a 1/3 hp sump pump.[6] Your appliance's nameplate beats both.
- Usable energy: EcoFlow estimates runtime as watt-hours × 0.85 ÷ device watts. It says actual results vary with load, temperature and inverter efficiency.[4]
- How long each item runs is the number nobody can publish for your house. Furnaces and sump pumps cycle on and off with the weather, your insulation and your water table. Start with the examples and adjust.
Furnace blower
A gas furnace still needs electricity for its blower and controls. The blower is the big draw: Champion lists 300 to 800 running watts for a 1/2 hp furnace fan, and up to 1,600 watts to start.[5] Honda's figures are higher still.[6] At 800 W running a third of each hour, the blower alone uses about 6,400 Wh a day. That would drain a 4,096 Wh DELTA Pro 3 in about 13 hours at an 85% usable share.[3][4]
So a power station buys you hours of heat, not days, unless you can recharge it. If your furnace is hardwired, it can't plug into a station's outlet. Connecting it safely needs a transfer switch or interlock installed by a licensed electrician; our interlock vs. transfer switch guide explains the options. For multi-day outages, compare a fuel generator in our generator vs. power station guide.
Sump pump
Champion puts a 1/3 hp sump pump at 500 to 800 running watts and 1,000 to 1,600 starting watts; a 1/2 hp pump at 800 to 1,050 running and 1,300 to 2,150 starting.[5] The starting figure is what decides whether a station can run it. The River 2 Pro's surge rating is 1,600 W,[1] the same as the top of Champion's range for a 1/3 hp pump, which leaves no margin. A 1/2 hp pump can need more than that.
Energy use depends on how often the pump runs. At 800 W for 5 minutes an hour, it uses 1,600 Wh a day, which a 2,048 Wh Delta 2 Max covers for about a day per charge.[2][4] In a wet thaw it may run far more.
CPAP
ResMed's AirSense 11 user guide lists a 65 W power supply, with typical power use of 56.1 W and peak power use of 73.2 W.[7] At 56.1 W for 8 hours, a night uses about 450 Wh. That's about 1.5 nights from a 768 Wh River 2 Pro and about 3.9 nights from a 2,048 Wh Delta 2 Max at an 85% usable share.[1][2][4] ResMed also sells an Air11 DC/DC converter for the AirSense 11.[7] Check with your equipment provider before running your machine from any battery, and look up your own machine's figures if you have a different model.
Cold-weather limits
Batteries have temperature ranges. EcoFlow rates the River 2 Pro to discharge from 14°F to 113°F and charge from 32°F to 113°F.[1] It rates the DELTA Pro 3 to charge from 0°C to 45°C and discharge from -10°C to 45°C.[3] A station left in an unheated garage during a cold snap may not charge at all. Keep it inside, in a heated room. A power station has no engine exhaust, which is why it can sit indoors; a fuel generator never can (see our generator vs. power station guide).
Frequently asked questions
How long will a power station run a CPAP?
ResMed lists typical power use of 56.1 W for the AirSense 11. For 8 hours a night that is about 450 Wh. A 768 Wh EcoFlow River 2 Pro covers about 1.5 nights at an 85% usable share, and a 2,048 Wh Delta 2 Max about 3.9 nights.
Can a portable power station run a furnace?
It can run a furnace blower if the station's continuous and surge ratings cover the blower, and if the furnace can be connected safely. Blowers draw hundreds of watts, so runtime is measured in hours, not days. A hardwired furnace needs a transfer switch or interlock installed by a licensed electrician.
Will a power station run a sump pump?
A 1/3 hp sump pump can start on a station with enough surge rating: Champion's chart puts its starting draw at 1,000 to 1,600 W. How long it lasts depends on how often the pump runs, which you can set in the calculator.
Do power stations work in the cold?
They have temperature limits. EcoFlow rates the River 2 Pro to discharge from 14°F and charge from 32°F, and the DELTA Pro 3 to discharge from -10°C and charge from 0°C. Keep the station in a heated space.
Sources
- EcoFlow, River 2 Pro Portable Power Station product page and specifications. us.ecoflow.com/products/river-2-pro-portable-power-station
- EcoFlow, Delta 2 Max Portable Power Station product page and specifications. us.ecoflow.com/products/delta-2-max-portable-power-station
- EcoFlow, DELTA Pro 3 Portable Power Station product page and specifications. us.ecoflow.com/products/delta-pro-3-portable-power-station
- EcoFlow (Ireland site), FAQs: "How do I estimate runtime?" ecoflow.ie/faqs/
- Champion Power Equipment, generator wattage chart. championpowerequipment.com/generator-wattage-chart/
- Honda Power Equipment, generator wattage estimation guide. powerequipment.honda.com/…/generator-wattage-estimation-guide
- ResMed, AirSense 11 user guide: power supply and power consumption specifications (copy hosted by Apria). apria.com (PDF)