How I test& select gear
Why trust me
I'm Leo, an electrical engineer and vanlifer since 2019. I've built out 3 vans from scratch — my first Ducato taught me one thing: when you get to the electrical system, it's chaos. Contradictory forums, incomprehensible Excel spreadsheets, and zero reliable tools for proper sizing.
Result: I ordered the wrong cables, nearly fried my inverter on day one, and lost three weeks redoing everything. VanPowerCalc was born from that frustration. I built the tool I wished I had, and the gear recommendations are the natural extension of that approach.
Important: no brand pays me for placement on this site. I don't do sponsored content. When I recommend a product, it's because I would use it myself in my van.
How I select products
For each category (batteries, solar, wiring...), I start by combing through Amazon reviews. Not 10 reviews — more like 100 to 300. I look at overall ratings, but especially the 1 and 2 star reviews: that's where you find the real issues (BMS failing after 6 months, connectors too fragile, non-existent support).
Then I cross-reference with vanlife community feedback: forums, Facebook groups, Reddit r/vandwellers and r/vanlife. When a product keeps coming up positively across these three sources, that's a good sign. When I can, I test it myself in my 12V setup.
Last criterion: availability on Amazon. Not out of laziness, but because it's the easiest way for you to order from anywhere in Europe, with reliable support and free returns if the product doesn't suit you.
The VanPowerCalc Score
Each recommended product receives a VanPowerCalc Score out of 100, calculated from 5 weighted criteria. This score lets me compare products objectively and only keep the best ones.
Price must be justified by quality. No overpriced gadgets, no cheap stuff that breaks after 3 months.
Amazon rating, review volume, and long-term feedback from vanlife forums.
A beginner should be able to install it with a tutorial. Standard connectors, clear manual.
Suitable dimensions, 12V/24V voltage, resistance to vibrations and moisture.
Good support makes all the difference when you're stuck in a parking lot in Portugal.
Ad — Affiliate transparency
Links to Amazon (and other Awin partners) are paid affiliate links. If you buy through these links, I earn a small commission at no extra cost to you. This is what allows me to keep VanPowerCalc free, pay for hosting, and keep developing new features.
I only recommend products I would use myself. If a product doesn't pass my criteria, it doesn't appear on the site, even if the commission would be attractive. My credibility is worth more than an Amazon commission.
Sources & technical standards
All VanPowerCalc calculations are based on international standards and verified electrical engineering formulas. Here are the references used.
Normes / Standards
Extra-low-voltage DC electrical installations (≤50V) on recreational craft — applied to 12V/24V onboard systems (reference for cable sizing and protection).
Habitable leisure vehicles — 12V DC low-voltage electrical installations. European standard specific to motorhomes and campervans.
International standard for low-voltage electrical installations — used as reference for cable cross-sections and fuse protection.
Sources externes / External Sources
Solar irradiation data by location — the basis of our solar calculations.
Datasheets and technical specs for MPPT controllers, inverters, LiFePO4 batteries.
International standard for low-voltage electrical installations — cable sizing reference.
Encyclopedia reference on lithium iron phosphate battery chemistry and specs.
Formules / Formulas
U = R x IFoundation of all electrical calculations: voltage = resistance x current.
Ah = (Wh/d x days) / (V x DoD)Battery sizing based on daily consumption, desired autonomy, and depth of discharge.
Wp = Wh/d / (PSH x eff)Panel sizing based on peak sun hours and system efficiency.
mm2 = (2 x L x I) / (sigma x Vdrop)Minimum cross-section to keep voltage drop below safety threshold (ABYC E-11: 3% critical circuits / chargers, 10% non-critical / lighting).
t = C / I^kCorrection for actual capacity of lead-acid batteries (AGM/gel) at high discharge rates. Does not apply to LiFePO4.
Contact me
Got a question about a product? Think one of my recommendations needs revisiting? Found a better product I should test? Write to me.
leo@vanpowercalc.comUser feedback is the best way to improve recommendations. Several products on the site were added following community suggestions.