How long will a VTOMAN FlashSpeed 1500 run a gas combi boiler?
About 18 hours — 17 h 52 min typically, from 16 h 49 min in the worst case to 18 h 55 min at best. That assumes a gas combi boiler pulling 85 W for 60% of the time (average 51 W), plus the station's 12 W AC mains socket overhead — 63 W in total out of 1,125 usable watt-hours.
The gas makes the heat, so a battery only has to run the fan, pump and controls. Most boilers are wired into a fused spur rather than a plug, and some will not light on a station’s ungrounded output — read the boiler guide before relying on it.
Before you rely on it
The battery is the easy part. Most boilers are wired into a fused spur with no plug, and some will not light on a station's floating output because they sense the flame through earth. The boiler guide explains both problems and who can fix them.
The numbers
| Setup | Average draw | Cautious | Typical | Best case |
|---|---|---|---|---|
| 1 × gas combi boiler, UK 230 V | 63 W | 16 h 49 min | 17 h 52 min | 18 h 55 min |
| 2 × gas combi boiler, UK 230 V | 114 W | 9 h 17 min | 9 h 52 min | 10 h 27 min |
| 1 × gas combi boiler, US 120 V | 63 W | 16 h 49 min | 17 h 52 min | 18 h 55 min |
- 2.2 nights of eight hours, or 0.74 days of continuous running.
- Usable energy: 1,125 Wh of the 1,548 Wh on the box, after chemistry, inverter losses and the reserve.
- To keep it going for a full 24 hours you would need about 2,081 Wh of rated capacity — 1.3× this station.
- Start-up: the gas combi boiler asks for 85 W at switch-on against this station's 3,000 W peak — comfortable.
Buy the VTOMAN FlashSpeed 1500
If this is for a power cut
Heating is what a battery does worst. In a power cut, warming people rather than rooms goes much further, and none of this needs a socket.
Without a power station: a 20,000 mAh power bank runs a USB heated throw for about 7 h 24 min. See the power bank numbers.
Hot water bottle and a vacuum flask. Boil water while you still can, keep it hot in a flask, and refill the bottle through the night.
Look for: A bottle made to BS 1970 in the UK, and a flask of a litre or more.
Hand warmers. Air-activated packs give hours of heat with no power at all, and a pocketful helps children and older relatives.
Look for: Long-duration packs, and the expiry date on bulk boxes.
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More: How to keep warm in a power cut, and the power cut essentials list (US edition).
What changes the answer
| If instead… | Typical runtime | Change |
|---|---|---|
| The pack is two years old | 16 h 26 min | -8% |
| The pack is five years old | 14 h 17 min | -20% |
| It is −10 °C outside | 15 h 11 min | -15% |
| You run it flat, no reserve | 19 h 50 min | +11% |
| You keep 20% back | 15 h 52 min | -11% |
If you need it to run longer
These run a gas combi boiler for at least twice as long as the VTOMAN FlashSpeed 1500 does, cheapest first.
| Station | Wh | Typical | Indicative price |
|---|---|---|---|
| EcoFlow DELTA Pro | 3,600 | 37 h 55 min | £2,499 / $2,699 |
| EcoFlow DELTA Pro 3 | 4,096 | 41 h 56 min | £2,799 / $3,199 |
| Anker SOLIX F3800 | 3,840 | 40 h 27 min | £2,999 / $3,499 |
| Zendure SuperBase V4600 | 4,608 | 47 h 10 min | £2,999 / $4,999 |
The cheapest step up: EcoFlow DELTA Pro
Amazon and approved-programme links are affiliate links; the site may earn a commission at no extra cost to you. Links marked “official site” are untracked. Prices and stock change constantly — check before you buy.
Smaller options that still work
| Station | Wh | Typical | Weight | Indicative price |
|---|---|---|---|---|
| Pecron E1500LFP | 1,536 | 17 h 43 min | 17.4 kg | — / $549 |
| Bluetti AC240 | 1,536 | 17 h 10 min | 33 kg | £1,099 / $999 |
| Bluetti AC180P | 1,440 | 16 h 37 min | 16 kg | £899 / $649 |
| Jackery Explorer 1500 Pro | 1,512 | 16 h 31 min | 17 kg | — / $1,699 |
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