Solar HW or Heat Pump

Will be building on a small rural property outside Canberra later in the year and most stumped on the best Hot Water system to got with. In an urban setting I prefer instantaneous gas because I hate wastage (I’m currently in a rental with a gas tank constantly heated and it makes me cringe). This will usually be just for one person, sometimes 2 (both very energy efficient and water wise). At the moment I’m leaning towards solar hot water (evac tube) with an LPG booster (the smallest I’ve seen is a 180L tank) but part of me is now wondering whether a heat pump (ie Bosch, Sanden Eco, Stiebel Eltron) might be better if I dump excess power into it (I will have solar PV just deciding whether to buy a transformer to connect to grid or go fully off grid with solar/wind).
Anyone have any recommendations as which would be the most efficient for one person low water user, in a rural setting outside Canberra (frosty but no snow)?
Anyone seen a Solar Hot Water heater (evac tube) with a tank smaller than 180L (suitable for 800m altitude)?

Hey @Svarky, do you have any insight into this one?

See our Solar Power Florida page:

The heat pump is definitely the most efficient option here… or heat pump combined with solar evacuated tube but this probably overkill as you stated you are very water wise.

As for going completely off-grid I would definitely keep the grid connection as it will enable you to feed-in excess solar and get some credits. More importantly the battery capacity required will be much smaller and more affordable. Off-grid systems require very large battery banks to allow for multiple days of autonomy (during bad weather events) and also a backup generator for those extreme prolonged winter storms.

This article will also help…

1 Like

I just had this same discussion with the Director of the Florida Solar Energy Center a few weeks back. In prior homes I had a thermal solar panel and loved it. Last system was installed in 2006. That house sold 6 months ago though with a working system. The Director also installed the same year. He told me he removed his now non-working system last year and replaced it w/ a heat pump and PV solar. He insists this is now a much better way to go.

This is how he explained it to me. It will cost about the same to install a heat pump and solar panels but this way whatever is not used to heat water for your house can be used for other electrical needs. He says that the heat pumps now are so efficient now that it makes more sense to do it this way. Having solar thermal alone limits you. Few seem to be a big fan of instant water heaters any longer because you are then using gas and it is expensive to get one that can handle creating hot water fast enough. We have gas now and are planning for how to do this since ours is rusting.

Hope this helps,


1 Like

Thanks for that Svarky. Partly because of your comment and some other things we’ve read we’re now looking at the smaller Sanden Eco HP as the likely option. I actually like the option of combining it with some evac tube panels but I think you’re right it would probably be overkill (same as I like the idea of combining it with a heat jack from the wood oven but distance rules it out I think and probably also overkill - I just like getting the most out of everything ;)).
Wrt to the grid connection there isn’t actually one there yet (though I have poles on my property at least). If we share the cost of transformer and pole with our new neighbour (also a new build) it would be about 21K for the grid connect which we are now leaning towards as a long term investment. That way we get some back in feed in, and I like the idea of excess we generate not being wasted and feeding the grid. Ideally I want a wind/solar off grid system but the cost is probably a little more than we can budget for right now.