Heat pumps and photovoltaics are now the most efficient combination for heating, cooling, and meeting a home's energy needs. However, one of the most common mistakes we see in practice is poor planning and getting the decision sequence wrong.
The question is simple: should we design the heat pump first or the photovoltaic system?
The question is simple: should we design the heat pump first or the photovoltaic system?
The answer is clear: the heat pump first, then the photovoltaics. Here's why.
1. The heat pump determines your home's energy consumption
A heat pump is not just another electrical appliance. It is the home's primary energy consumer, especially during the winter months.
Its capacity (e.g. 8kW, 12kW, 16kW), its type (air-to-water, geothermal), and how it operates all determine:
Its capacity (e.g. 8kW, 12kW, 16kW), its type (air-to-water, geothermal), and how it operates all determine:
- annual consumption in kWh
- peak loads
- the property's energy performance in winter
If the photovoltaic system is designed before a heat pump assessment has been carried out, the result is almost always incorrect sizing.
2. Heat loss and proper assessment: the real starting point
No heat pump should be selected “by eye.”
The right process starts with:
The right process starts with:
- the building's insulation condition
- floor area and room height
- the type of heat emitters (underfloor heating, low-temperature radiators, fan coils)
- the climate zone and actual heating needs
Only then can we determine the right heat pump capacity, which in turn gives us a realistic estimate of annual electricity consumption.
3. Photovoltaics are designed to meet needs—not assumptions
Once we know how much energy the home will consume with the heat pump operating at full capacity, and only then, can we design the photovoltaic system properly.
At this stage, we take into account:
- total annual consumption (home + heat pump)
- seasonality (winter vs. summer)
- available space for panels
- the net billing arrangement
- the possibility of adding a battery in the future
This helps us avoid both undersizing (too few panels, limited benefit) and oversizing (unnecessary cost).
4. Why the sequence matters (financially, too)
When the sequence is wrong, we often see the following problems:
- a photovoltaic system that “isn't enough” for the heat pump
- a heat pump that's oversized for the home
- savings expectations that aren't met
- the need for retroactive changes at additional cost
By contrast, with proper planning from the outset:
- the heat pump operates within its optimal efficiency range
- the photovoltaics meet actual needs
- the payback period is reduced
- the system is ready for future upgrades
5. The right design approach, step by step
The optimal approach is as follows:
- Energy and thermal assessment of the property
- Selection and proper sizing of the heat pump
- Calculation of annual consumption under real-world conditions
- Design of the photovoltaic system based on this consumption
- Planning for a future battery or electric vehicle
This approach ensures maximum efficiency, savings, and reliability.
The heat pump and photovoltaics are not two independent decisions. They are one integrated energy system.
Anyone who designs the photovoltaics first is designing blind.
Anyone who starts with the heat pump and the home's actual needs builds a system that delivers.
Anyone who designs the photovoltaics first is designing blind.
Anyone who starts with the heat pump and the home's actual needs builds a system that delivers.
Good planning doesn't cost more.
