Sorry for resurrecting this thread, but may be able to save you some money. Be extra careful if you intend to purchase an electric compressor-based dehumidifier for your caravan. Only a few of them work in temperatures lower than 5 deg C. That also includes Peltier effect units, although those are cheaper and consume less power. This is not too good for UK winters.
The dessicant systems have varying degrees of success but will work normally at fairly low temperatures.
The Ebac 18 litre Powerdri Dehumidifier (around £200) will function down to 2 deg C but with many of these, they only really work well with higher temperatures. This is expensive so a good idea if you use it for the house and occasionally the caravan.
B&Q have sold small dehumidifiers for a while, if you catch them right in the sale, you could end up with one for £50. Although cheap, they have LG compressors and do stand up to a lot of abuse. Ours lasted three years whilst being thrown around the caravan and dropped twice from the sink onto the floor (which is why it probably has a siezed compressor now).
There are many good reports about the dessicant units which contain heaters, usually these are for cupboards but can work in cars or vans. Cheap at £15 for two from Amazon.
The end result is that we enjoy the van more when it's been dried using the dehumidifier, it's also easier to heat. Even sleeping and breathing produces plenty of damp air.
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