Tips From Our Experts

Steven asks: How do I go about establishing my power needs to be able to then look at what level KW I need my solar panels to be? Also, re solar hot water, is it better to have gas boosted or electric?

Solar Hot Water: Gas Boosted or Electric

Steven asks:

How do I go about establishing my power needs to be able to then look at what level KW I need my solar panels to be? Also, regarding solar hot water, is it better to have gas boosted or electric?

Our expert’s answer

Firstly, on solar hot water, typically the gas or electric system choice will be dependent upon whether you are connected to the gas network or not.

If you have a choice between either, then rough rules of thumb to keep in mind are:

  • electric boosted systems will generally be cheaper upfront – and may have more expensive running costs (unless you can maintain an off-peak tariff to boost them from);
  • gas boosted systems will generally be more expensive upfront – and may have lower running costs (but gas prices are on the rise over the next 5 years [more so than electricity], and so this may not be the case in the longer term;
  • evacuated tube systems will be more expensive upfront than flat plate, but will also be more efficient and therefore lower your running (and therefore total) costs over the life of the system.

To understand the best project economics for your circumstance, you really have to financially model the full capital and running costs of each system type and compare them over the life of the system. We can help you do this if you need.

Also, if you have a solar PV system, that is powering the electric boost on your solar hot water system, this again may make the electric boost SHW system even cheaper. You may also want to think about heat pump hot water systems in this regard, with some of these now being more efficient, and having a lower installed cost than solar hot water.

Hope that helps, happy to help further if you need more details.

For further tips on efficient hot water systems and solar PV systems, see the 17 Things™.

John Knox

John Knox

The technical advice provided by the Alternative Technology Association as part of the ‘Ask an Expert’ forum/website, in relation to home and building sustainability improvements, is general in nature only. The impacts of specific energy or water saving or sustainability products will depend on how and where the are used and located, and particularly for larger investments, we would always suggest users seek a specific assessment from an appropriately qualified building designer or service / product supplier.

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