Gerrib,
There are other alternatives to consider too. Please look at heat pump hot water systems and continuous gas systems while you are doing comparisons with the solar.
Heat pumps run like an air conditioner system. They pump gas around a condenser which produces heat at one end and cool at the other. Air conditioning systems take the heat from the room, pump in cool air and put the heat outside. Heat pumps take the heat from the outside atmosphere, put it into a water tank and put the cool back out to the atmosphere. As they don't usually have a heating element they are electrically efficient compared to normal element type hot water heaters.
A heat pump may reduce your hot water electricity costs quite substantially.
Try and choose a heat pump that does not have an electric booster element. Some companies make the water tank too big and the condenser to small and to solve the problem that the condenser does not heat the water effectively they put in an old style element. Don't choose that style because it has not been designed properly in the first place and the element wont reduce your bill as much as it should.
Either way I think you need to do something about your hot water system before you choose solar or not. The system you have is over 20 years old. That is a great life for a hot water system, but it may well be coming to the end of its life. I would hate for you to spend a swag of money on a 3kw solar system, sized on your current hot water system only to have it die in 12 months time and be up for the cost of either solar or heat pump or renew your old system.
On the solar system... We are a house hold of 6 with a 2.2kw system. I would think that a house of usually 1 should not need a 3kw system. Reducing the electricity usage will go a long way to reducing the size of the solar system you will need. I would agree that a great deal of your 11pm to 7am usage would come from the old hot water system, but it can be hard to tell unless that is the only appliance hooked up to the off peak 1 rate. If you are on a general time of use metering, everything that runs at night will be added to the 11pm to 7am slot.
I would agree that a 3kw system for your $800 or so bill is over the top.
If I were you I would set about replacing the hot water system. Your choices are:
Solar hot water (flat plate, evacuated tube - but I would try for the tank higher than the collector style because that does away with the need for pumps to circulate the water due to thermosyphon effect). You are in a rural setting so it may be feasible to have the solar hot water on a frame at ground level rather than the lot on the roof.
Heat pump, but remember to get one without a booster designed in because they are bad design.
Bottled gas with a gas hot water system. This may well be an option too. Reduces your electricity bill, continuous gas hot water removes the need for a water storage tank which loses heat all the time. For a single person house this may well serve you better. For the times you only need hot water it heats what you need but can also run for when the guests come. The storage tank type of water system really needs to be sized larger than for just your own needs due to the guests coming. The bottled gas option also gives you the option of gas heating for the winter time too.
I would weigh up the costs of improving your hot water system first, get that sorted out and review your electricity bill 12 months after you have changed the hot water system over. That way you can size your solar panels to your electricity needs now rather than base it on a 20 year old hot water systems electricity needs.
Posted Saturday 26 May 2012 @ 5:19:35 am from IP
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