Does anyone actually get the rated output from cheap PWM controllers in winter?

I picked up a 20A PWM controller off Amazon for about £14 to run a small shed setup — 200W panel feeding a pair of 100Ah leisure batteries. Summer was fine, no complaints. But now we're into the colder months and I'm noticing the controller seems to be cutting charging well below what I'd expect, especially on those bright but cold days where the panel voltage shoots up to around 21–22V open circuit.

From what I understand, PWM just clips the panel voltage down to match battery voltage, so all that extra voltage on a cold day is essentially wasted. I'm getting maybe 6–7A into the batteries on a decent January morning when I'd expect closer to 10–11A given the conditions. An MPPT would harvest that higher voltage properly, but they're obviously more expensive — even the cheapest halfway-decent ones are £40–60.

Has anyone done a proper like-for-like comparison between a budget PWM and a cheap MPPT (say a Renogy Wanderer vs a Victron 75/15 or similar) over a full winter? Wondering whether it's actually worth the upgrade for a modest shed setup or whether I'm just chasing numbers that won't make a meaningful real-world difference.

@T5Build this is a well-known limitation of PWM that catches people out. In winter your panel Voc climbs — I've measured 22V+ from a nominal 18V panel on a cold clear morning — but PWM simply clamps that down to battery voltage (~12.4V float), throwing the difference away as heat. You're potentially losing 30-40% of available current before inefficiencies even factor in.

Your 200W panel through a proper MPPT like a Victron 75/15 would harvest meaningfully more on those low-angle winter days. The Victron holds its value secondhand too if you ever upsize.

The £14 controller isn't lying about its 20A rating — it'll pass 20A — it just can't extract 20A from a cold high-Voc panel when battery voltage is depressed. Cold weather is precisely where MPPT earns its premium.