Bosch Compress 3000 Review
28 Dec 2025In mid 2019 we used a state government subsidy to replace our gas hot water system with an electric heat pump one, planning to power it as much as possible while the sun shines on our solar panels. We chose the Bosch Compress 3000 - here’s a belated review.
It’s an all-in-one unit, with the compressor sitting on top of a 270 litre tank. It draws 600W for the heat pump, and there’s a backup heating element for temperatures below 0℃ (which we’ve disabled). I believe most owners configure it to run on a timer (either at night for cheap power, or during the day for solar power). However the controller can also integrate with some solar inverters (like our Fronius Galvo) and run the heat pump when excess solar power is being exported to the grid. Free hot water!
It’s not the most efficient unit around. This table from the manual shows typical heating times under various conditions.
At 15℃ ambient temperature, the Coefficient of Performance (COP) is 3.3. Over an hour of operation, about 0.6 kWh of electricity will be consumed, and about 1.98kWh of energy will be added to the water.
We’ve found it an adequate system but if we were choosing again we’d choose a system that can heat water faster.
Between sunset and 9am, we slowly consume hot water with two kids to bath, two adult showers, some dishes, and an occasional hot load in the washing machine. If the following day is around 15℃, our experience is the above table is roughly accurate - it’s not uncommon for the heat pump to run for ~8 hours, consuming ~4.8kWh.
On a sunny winters day, we get about 5 hours of good output from our north-facing solar panels. 5 is less than 8, so many day over winter we heat some of our water with grid power. Adding additional solar panels won’t help much - north facing panels won’t extend the 5 hour generation window, and west facing panels are difficult on our roof.
There are more efficient (and expensive) options that provide an interesting comparison. Sanden offer a 315 litre tank that draws about 1kW and has a COP of 4.7 at 15℃ ambient temperature. Over an hour of operation, about 1 kWh of electricity will be consumed and about 4.7kWh of energy will be added to the water. That’s more than double the heat output of the Bosch - partly due to the heat pump drawing more power, and partly due to higher efficiency. Reclaim have an alternative that claims similar performance.
At that rate, the full tank can be heated in about 4 hours. Fast enough to be 100% solar powered on a sunny Melbourne winters day.
In 2019 neither the Sanden or Reclaim units supported integration with a solar inverter - the feature that sold me on the Bosch. I believe they have some integration support now, howver it turned out less valuable than I assumed and in hindsight it’s a nice to have rather than a must have feature. We really don’t like lukewarm showers and to minimise the risk of one we’ve found the heat pump needs the option to run daily for long enough to completely heat the tank ( in winter: 8+ hours for the Bosch, 4+ hours for the Sanden/Reclaim), even if the sun is hiding. Most days it won’t need to operate for the full window, but occasionally it will and that’s super valuable. Defining that window with a simple timer is probably good enough.
If you’re in the market for a heat pump hot water system in Ausralia, I highly recommend joining the My Effiicient Electric Home group on facebook. Brian Tehan has posted a spreadsheet comparing common options in Australia and the numbers are interesting. Here’s a sneak peek at the estimated tank heating times - pay more attention to them than we did!
Now that we have the bosch, we obviously won’t get rid of it. It does the job! I’m tempted to make the most of it and explore replacing the inverter integration with something more custom, maybe allowing the heat pump to run when we’re exporting to the grid or when our time of use power prices with Amber Electric are cheap.