About Solar Power Auditor

Why this exists

Buy a portable power station and you are buying a number. "1,024 watt-hours." "2,042 watt-hours." That number is on the box, in the product title and in every advertisement.

You don't get all of it. Between the cells and the AC outlet sit an inverter, a battery management system and a reserve the manufacturer keeps back to protect the pack. On my bench, eleven units delivered between 80.1% and 92.1% of their ratings. Manufacturers don't generally publish where their product falls in that range.

Two of the units I tested were both rated at 1,024 Wh. One delivered 892 Wh and the other 862 Wh. Nothing on the box would have told you which was which.

Who I am

I'm Scott Caine. I buy, test and write up every power station on this site, and every "I" you read here is me.

The testing happens where these units get used: my kitchen and garage, my home office, my van, campsites, and the deck where the solar panels go out. My house has a well pump, a 2,400 W roof array and a transfer switch fitted by a licensed electrician, which is how the two largest units were tested on real household circuits and a real 240 V load.

I also run a ResMed CPAP at night, so the CPAP recommendations come from nights spent sleeping next to these units as well as from the arithmetic.

What I do

I buy every unit at retail. No manufacturer has supplied, loaned or discounted any of the hardware on this site.
I drain every unit on the same bench. Charged to full, run at a constant 300 W until it shuts off, with a meter at the AC outlet logging every watt-hour. I also time the wall recharge, weigh it, measure the noise, find the overload trip point and log the solar input it actually accepts.
I live with each unit for a month or more — between 27 and 44 days each so far — through outage drills, camping weekends, van trips, CPAP nights and solar charging.
I score every unit the same way. A measured score from one published rubric is blended half-and-half with nine hands-on ratings, and the sum is printed on every review.
I show my working. Runtimes are calculated from my measured capacity using fixed assumptions, and the arithmetic sits under every figure.
I cross-check against independent labs where one has published a figure. My capacity measurements have landed within 18 Wh of OutdoorGearLab's on every unit where it has one.

The full procedure is on how I test and rate.

⚠ What

I've used each unit for weeks, not years. Cycle life and long-term capacity loss come from the manufacturers' ratings, and I report them as claims. My results come from the unit I tested, in my conditions. My CPAP draws less than most machines (about 23 W), my fridges are my fridges, and my sun is my sun. Each review keeps measured, observed and calculated figures apart so you can tell how far your situation is likely to differ. Eleven units from four brands, two or three per brand, is enough to see tendencies. It isn't enough to declare one brand better than another, and where a conclusion rests on a single unit, I say so.

Standing editorial policy

I will:

label every figure as my measurement, a manufacturer's claim or a calculation, and keep the three visually distinct;
publish the test procedure and the arithmetic behind every score and runtime;
name the independent lab whenever I use its figure as a cross-check;
keep the score and my pick separate: the score is formula, the pick is my judgement, and I say why when they differ;
correct errors on the page, with the date, rather than silently.

I will not:

claim to have tested hardware I haven't tested;
accept sponsored placements, paid scores, free or loaned units, or press pricing;
run display advertising;
use anything other than the manufacturer's list price in a score, a table or a cost-per-watt-hour figure;
rank a unit I haven't measured.

Get in touch

Corrections, disagreements and requests for units to cover all go to the same place: the contact page. If I've got something wrong, I'd rather hear it from you than leave it up.