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Hi is there anybody out there that knows anything about or has had experience of air-source heat pumps? We're off grid and reliant on batteries and 24v inverter. Would it be possible to run one using these? Or would we be running our batteries down too fast, in which case we would be dependent on the generator which would be a complete waste of effort and energy.

No direct experience, but I am considering them too. The author of this rather good sustainable energy e-book thinks they are the way to go http://www.withouthotair.com/download.html

FWIW there are many DIY models on ebay .... I am tempted :-)

As always advised - insulate as much as feasible first, before looking at heating.

Typically you'll need about 1KW input for an ASHP that will give you 3-5KW output... will your batteries cope - how are you generating power?

We're currently charging our batteries by running the generator for 2-3 hours every other day or every third day if we can get away with it, this doesn't fully charge the batteries however.

The washing machine is not wired through the inverter so we generally need to use the genny for this (We're pretty filthy after 3 days!) and also for other high draw appliances. We would like to lessen our dependence on the generator and will also be looking into wind/solar to replace as much as possible when funds allow.

When you say 1kw is this a constant draw or is it cutting in and out?

Hi

My otherhalf sells ASHP's as well all the other renewables. He reckons as advised above insulate everywhere as much as possible, then do it again. Likely that a heat pump will be drawing quite a bit of power for long periods of time. A correctly specified system should be able to run for as long as possible to avoid cycling the compressor doing this will shorten its life span. So his advice is don't bother with a heatpump the cheap ones are inefficient and will claim wonderous COP's but are anything but useless in winter. The good efficient ones are expensive and will still nail the batteries in a short period of time.

Sorry if this isn't what you wanted to hear

Interesting comments Mew - apart from price - what is it that differentiates a good ASHP from a useless one for winter heating? what does one look for?