Inflatable hot tub (Lay-Z-Spa) on a portable power station

From Bestway's Lay-Z-Spa owner's manual and the Lay-Z-Spa UK FAQ (220–240 V, 50 Hz). These are Bestway's figures, not QuietWatt measurements:

• Heating on: 2,050 W at 20 °C, which is a 2,000 W heat element plus a 50 W circulation/filter pump. The filter starts automatically whenever heating is on.
• Massage (AirJet blower): 800 W.
• Filter only: 50 W.
• Heating rate: about 1.5–2.0 °C per hour on 2–6 person models (about 1–1.5 °C/h on the larger Monaco), with the cover on.
• Bestway's own heat-up times to 40 °C: 18.5 h from 10 °C, 15 h from 15 °C, 11.5 h from 20 °C, 8.5 h from 25 °C, 5.5 h from 30 °C (when the water and the air start at the same temperature).

Sources: Bestway Lay-Z-Spa owner's manual (PDF) and Lay-Z-Spa UK FAQ. Other inflatable spa brands: read the rating plate on the pump. QuietWatt won't guess.

Heater minutes ≈ station Wh × 0.85 ÷ 2,050 W. The 0.85 is QuietWatt's usual allowance for inverter losses. These are planning estimates, not tests.

• Full Explorer 2000 Pro: 2,160 × 0.85 ≈ 1,836 Wh ÷ 2,050 W ≈ 54 minutes of heating, which is roughly +1.3 to +1.8 °C at Bestway's 1.5–2.0 °C/h.
• Full SOLIX C2000 Gen 2: 2,048 × 0.85 ≈ 1,741 Wh, which gives about 51 minutes and roughly +1.3 to +1.7 °C.
• A full heat-up from 15 °C: Bestway quotes 15 h. At 2,050 W that's about 31 kWh, or around 17–18 full charges of a 2 kWh station.
• Physics check: heating 669 L (a 2–4 person Lay-Z-Spa) by 25 °C takes at least 669 × 25 × 1.163 ≈ 19.5 kWh before any heat escapes, so no portable station gets anywhere close.

The honest answer: heat the tub from a grounded, RCD-protected mains socket, as Bestway specifies. A portable station is the wrong tool for heating because of both the watts and the kWh. Solar won't close the gap either: see how many solar panels.

• Freeze protection kicks in automatically. Bestway's manual says that if heating is on and the water drops below 6 °C, the heater warms it to 10 °C. On a station that's a 2,050 W load, so a 1,800 W station will trip. In a winter outage, switch heating off and run filter only, then drain the tub if the cut will be long and the frost hard. The manual also warns against switching the heater off below 6 °C when the tub is full, so this is a trade-off.
• Bestway says no extension leads. The pump has a 7 m cable and a built-in PRCD, and the socket should be grounded, RCD-protected, at least 4 m from the tub and 1.2 m off the ground. Whether the PRCD will reset on a given station's AC outlet is TBD, so ask Bestway before you rely on it. Not electrical advice.
• Keep the station dry. Portable stations aren't rated for splash zones. Keep it well away from the water, as you would the socket.
• The fridge and the freezer come first. In a real outage the same kWh will keep food cold for much longer. See fridge runtime and freezer thaw hours.