After installation: the two numbers you should know

Most guides end with the commissioning. Yet that is exactly where the part begins that decides the next twenty years: whether the system runs as it was calculated.

The good thing is: you do not need any specialist knowledge for this. Two meters and a glance every few months are enough.

Why two meters

The Vorarlberg guideline explicitly requires them: for self-monitoring of the seasonal performance factor, "a heat meter and a separate electricity meter must be present". The Upper Austrian data sheet confirms the same purpose — monitoring the efficiency of the system, "high proportion of heat provision with low drive energy".

There is a simple calculation behind this:

The electricity meter measures what goes in at the top.
The heat meter measures what comes out at the bottom.
The ratio of the two is the seasonal performance factor (SPF).

An SPF of 4 means: one kilowatt hour of electricity becomes four kilowatt hours of heat. Without the two meters, this number cannot be determined — then you are left with only the total electricity bill, and that mixes up the heat pump, fridge and everything else.

That is why the meters are also worthwhile where they are not mandatory. They cost little in the context of a heating investment and are the only way to prove a suspicion. "It seems to me it runs a lot" is not an argument to the installer. A measured SPF is.

What to look at and when

In the first week. Is the system running quietly, or does it switch on and off noticeably often? Frequent cycling is the typical sign of an oversized device or a system that has not yet been adjusted. Does it get evenly warm in all rooms?

In the first winter. When it is really cold, note down both meter readings once and repeat this after a few weeks. The difference in heat quantity divided by the difference in electricity gives the performance factor for this period — the most honest value, because it is created under the harshest conditions.

After the first year. The same calculation over twelve months is the seasonal performance factor. It is the number that counts.

If the number disappoints

Before you suspect the device, it is worth looking at three adjustments — in this order:

The heating curve. It is often set too steep from the factory. If you lower it step by step and observe whether it stays warm, you often get the biggest improvement here — without spending a cent.
The hydraulic balancing. If one room stays cold and the rest is overheated, it is missing or incorrect.
The hot water preparation. It runs at a significantly higher temperature than the heating and depresses the performance factor. Storage temperatures that are too high or heating up too frequently cost noticeably.

Only when all this is right and the number is still bad is it a matter of design or device — and then you have something in hand with the measured values.

What belongs in the documents

For the public grant, the Bestätigung über die ordnungsgemäße Inbetriebnahme (confirmation of proper commissioning) is required. Keep it, together with:

the commissioning protocol with the set parameters
the data sheet of the device
the invoices
the meter readings taken at the start

The last point sounds like a minor detail, but it is the reference point for every subsequent calculation. If you forget it, you can no longer evaluate the first year.

The one sentence you should say to the installer

“Please explain to me during the handover where I can read the two meters and how I adjust the heating curve.”

Ten minutes during the induction, and you can keep an eye on your system yourself for the next twenty years. A good installer will do this proactively anyway.