The question always arrives in the same form: “how many Wh do I need?”. It has no general answer, but it does have a method. It takes four steps and a quarter of an hour with a piece of paper.
Step 1 — List what you actually plug in
Not what you might plug in: what you do plug in. For each appliance, two pieces of information, both on the rating label or in the manual: its power in watts and the number of hours a day it runs.
Watch out for the fridge, the one genuinely tricky item: a compressor does not run continuously, it cycles. A model rated at 45 W draws in practice the equivalent of 15 to 20 W averaged over the day, more in strong heat. We work that calculation through in How many Wh does a van fridge need to run all night?.
Step 2 — Multiply, then add up
Watts × hours = watt-hours. That is the whole of the arithmetic.
- Camping fridge: 45 W, about 8 h of compressor over 24 h → 360 Wh
- Laptop: 60 W for 3 h → 180 Wh
- LED lighting: 10 W for 5 h → 50 Wh
- Two phones: roughly 30 Wh
- Fan: 40 W for 4 h → 160 Wh
Total: 780 Wh a day.
Step 3 — Add the losses
This is the step most online calculators skip, and it is the one that explains the disappointments. A station does not give back 100 % of its stated capacity: the inverter that turns the battery's direct current into 230 V alternating current takes its share on the way, and the electronics keep a margin at the bottom to protect the cells.
Allow 85 % of capacity actually usable. That is the figure we use in the runtime table on every product page, and it is deliberately cautious.
Our 780 Wh example therefore calls for a station of at least 780 ÷ 0.85 ≈ 920 Wh to last a full day without recharging.
Step 4 — Check the continuous output, not just the capacity
Two figures, two jobs. Watt-hours tell you how long it lasts. Watts of continuous output tell you what you can plug in at the same time, and that is an absolute limit: beyond it, the station shuts down to protect itself, whatever its reserve.
Add up the power of everything that could run simultaneously at the worst moment. A fridge starting while a kettle heats is 45 + 1,200 W. No station in the range will hold a kettle: it is written in black and white in the runtime table on every product page, rather than discovered in a motorway services car park.
What that looks like in practice
A weekend with no recharging, modest use — lighting, phones, a laptop: 300 to 500 Wh a day. The Volta 1000 and its 614 Wh are enough.
A week with a fridge running permanently: 700 to 900 Wh a day. You need the Volta 1600 and its 1,024 Wh, and a source of recharging.
Because that is the last point, and the most important: beyond two days, it is no longer capacity that counts but recharging. A well-angled 200 W folding solar panel returns 600 to 900 Wh on a fine summer day — roughly the daily consumption calculated above. It is that combination, not an oversized station, that lets you stay out for several days.