Electric Element vs Heat Pump Calculator – MC Electrical

(6) How much of your hot water will be supplied by solar? Well, again, this depends. Do you usually have 3.6kW element and 3.6kW of surplus solar for 2 or 3 hours a day? Or do you send very little solar power back to the grid? I think 80 per cent is generous if you have a large solar system. Remember, there will always be rainy days.

(7) How long will your resistive hot water tank last? Ask some plumbers, and they will tell you 20 + years. But I tend to think newer tanks were not made the same way as they used to be. I default on 15 years. The calculator will account for a percentage of the cost of the hot water system. For example, if you say the hot water system will last 20 years, then the calculator will only add half of the upfront price.

Heat Pump Calculations

Heat pumps consume a quarter of the energy of an electric element tank, so we have calculated this from your bill data.

(8) This price was just an over-the-phone estimate I was given for replacing an electric element with an iStore Heat Pump.

(9) Because a heat pump only draws about 1kW (compared to 2.4kW of 3.6kW electric element), it is much more likely that more of that will be supplied with surplus solar.

The iStore Heat pump does not need a Catch Relay or diverter. The iStore has a built-in timer. It can’t be switched on and off as often as a simple element, but because it only draws about 1000 watts, it will likely sit under your excess solar curve most of the time.

(10) While iStore has a 5-year warranty, from the conversations that I have had with experienced installers, it is fair to expect it to last at least ten years. Karl Jenson claims it will last 15,000 run hours, but that’s not backed up in any iStore document. As with the electric element calculations, if you estimate a heat pump will last ten years, the calculations will account for 100 per cent of the cost of the hot water system. Assuming the system will last 15 years, the calculations will allow for 66% of the cost.

Conclusion

There are so many variables to consider if you want to know if a heat pump is better for you than an old-school electric element tank.

• • • If you are now paying 30+ cents rather than 20 + cents for electricity
  • • If you use a moderate amount of hot water.
  • • If an electric element tank no longer lasts 20 + years, as I claimed.
  • • If heat pumps are close to the price of an old-school tank and a Catch Relay
    • If a heat pump will last 10+ years as Karl claims

Then I was wrong. Heat pumps are the more economical solution.