Water heating - Gas vs electric - which one would be more cheaper in Auckland?

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turtleattacks

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#303992 26-Mar-2023 21:35

Currently filled up the spa pool and starting to heat it up now during the 3-hours of free power we get from Contact Energy.

We also have gas, and obviously there's no free gas but promotions aside - has anyone done any calculation on what would be cheaper to heat up some water? Gas or Electric?

Edit: We have continual flow (i.e. no tank.)

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SomeoneSomewhere

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#3055066 26-Mar-2023 21:56

If you have a timer on the tank and a reasonable size tank, 3h a day is almost always going to be able to fill it. IOW it's free. Set the timer to run for another hour afterwards just in case.

dasimpsonsrule

147 posts

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#3055068 26-Mar-2023 22:01

Gas in bottles or natural gas? Last I checked LPG bottles are the most expensive way to heat water, then standard electric, then natural gas, and cheapest is heat pump

turtleattacks

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#3055071 26-Mar-2023 22:08

SomeoneSomewhere:

If you have a timer on the tank and a reasonable size tank, 3h a day is almost always going to be able to fill it. IOW it's free. Set the timer to run for another hour afterwards just in case.

I'm staying up till midnight to make sure it maximising the free power! Will do so for the next few days :D

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SomeoneSomewhere

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#3055078 26-Mar-2023 22:45

turtleattacks:

SomeoneSomewhere:

If you have a timer on the tank and a reasonable size tank, 3h a day is almost always going to be able to fill it. IOW it's free. Set the timer to run for another hour afterwards just in case.

I'm staying up till midnight to make sure it maximising the free power! Will do so for the next few days :D

Not quite sure what you mean by that - you're on (gas?) continuous flow now, so can't make use of it yet. Unless you're talking about the spa.

turtleattacks

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#3055080 26-Mar-2023 22:47

Not quite sure what you mean by that - you're on (gas?) continuous flow now, so can't make use of it yet. Unless you're talking about the spa.

We have 3 hours of free electric power from 9pm to midnight so I'm just staying up to make sure it's heating the spa water.

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Scott3

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#3055081 26-Mar-2023 22:57

turtleattacks:

Currently filled up the spa pool and starting to heat it up now during the 3-hours of free power we get from Contact Energy.

We also have gas, and obviously there's no free gas but promotions aside - has anyone done any calculation on what would be cheaper to heat up some water? Gas or Electric?

Edit: We have continual flow (i.e. no tank.)

Depends on your power and gas rates:

Electric for me is about 17c/kWh. When I priced out contact good nights for my location it was 24.2c/kWh. Assume 100% efficient for electric heating.

Natural gas (piped gas from the street), is typically around 7c/kWh. Assume 85% efficient water heater, so 7/0.85 = 8.23c/kWh

45kg (625 kWh) cylinders of LPG gas at say $100 each work out to 16c/kWh. 16/0.85 = 19c/kWh

9kg (123kWh BBQ) of LPG at say a $39 swap work out to 32c/kWh. 32/.85 = 37c/kWh

So if you have natural gas, that is way cheaper.

Otherwise, it largely comes down to your power & LPG rates. For me Power would probiably win, but on your good nights plan, LPG might take it out.

Note I didn't make any allowance for the dregs of LPG that are hard to use from the bottle.

Scott3

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#3055082 26-Mar-2023 23:06

SomeoneSomewhere:

Not quite sure what you mean by that - you're on (gas?) continuous flow now, so can't make use of it yet. Unless you're talking about the spa.

I imagine OP is deciding between putting cold water into the spa with a hose, and using it's integrated electric heater to warn it, and connecting the hose to a hot tap and having the gas water heater do the bulk of the heavy lifting.

Ultimately the cost is not massive. Say 1500L water going from 17c to 37c, will need 35kWh of energy. at 25c/kWh this is $8.75.

So the most convenient solution is likely to be the best, unless OP fancies a spa ASAP, in which case running a hot hose in will get the job done in under two hours, where as using the spa's built in heater at say 1500W (some can be double that), will take 24 hours.

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SomeoneSomewhere

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#3055284 27-Mar-2023 12:45

There's always this solution.