Solar and Air to Water Heat Pump Combination

Introduction

Investing in renewable energy technologies like solar systems and air-to-water heat pumps (AWHPs) can significantly enhance energy efficiency—but it often comes with high upfront costs. That’s why it's essential to carefully assess the benefits, limitations, and return on investment (ROI) of each technology, whether used independently or in combination. The goal is to maximize energy output per dollar spent and minimize the system's payback period.

Measuring Return: Energy Generation vs. Energy Savings: In energy efficiency projects, the “output” of your investment typically comes in two forms: 

1- Free energy (electricity or hot water) generated by solar panels (Potovoltaic or Thermal).
2- Energy savings achieved by replacing traditional electric or gas boilers with air-to-water heat pumps for both space heating and domestic hot water (DHW).

An effective investment strategy aims to maximize the ratio of energy output (or savings) to cost, ensuring optimal performance and economic viability.

In this blog we evaluate the impact of combining Solar Thermal or  Solar Photovoltaic with Air to water heat pump.

Combining solar energy with the air-to-water heat pumps offers several compelling reasons. Not only would the combination offset the electric power consumed by the heat pump or complement the thermal energy produced by the heat pump, but it can also provide a reliable backup during power outages. In such cases, solar power can replace grid electricity or help maintain the buffer tank at the desired temperature.

Solar collectors harness solar energy in two primary forms: Photovoltaic (PV) panels, which generate electricity, and Vacuum Tube (VT58) panels, which produce thermal energy. Choosing between these options depends on specific applications and regional considerations, which can make the decision process seem complex.

To better understand the most effective systems, we conducted simulations in major Canadian cities, comparing heating systems for both space heating and domestic hot water heating. We explored two scenarios: one combining an air-to-water heat pump with PV panels, and the other pairing the heat pump with VT58 panels.

Case Definition

The case we have considered is a 2000 ft2 , 4-person home with 10 m2 of south facing roof space available for either panel type. In that space, either 4 PV panels of 500 W each or 2 Vacuum tube (VT) panels of 30 tubes each fit. The space heating system consists of a 5-ton air-to-water heat pump, an electric back-up heater, a buffer tank, and either the vacuum tube (VT) panels or the photovoltaic (PV) panels.

The 2 scenarios are the following: Scenario 1 is the system using the PV panels along with the heat pump system, and Scenario 2 is the system using the VT panels with the heat pump system.

Both these scenarios were simulated in the following Canadian cities: St. Johns, Halifax, Toronto, Montreal, Quebec, Winnipeg, Saskatoon, Calgary, Edmonton, Vancouver, Victoria, Revelstoke, and Kamloops.

Scenario 1

Scenario 2

Results

The table below presents the results for Scenario 1: the system using photovoltaic panels with the air-to-water heat pump, highlighting how the solar electricity generated, the electric consumption and the overall heating energy demand for the system changes across the different Canadian cities:

The electricity consumption (in kWh) represents the total electricity Consumed by the DHW and space heating system, which includes the air-to-water heat pump, backup boiler, and pumps. The net electric consumption (in kWh) represents the total net electricity used by the heating system with the electricity generated by the photovoltaic panels taken out. The solar electrical energy generated (in kWh) is the electricity generated by the photovoltaic panels. The total system energy demand (in kWh) is the thermal energy effectively delivered for space heating and domestic hot water heating.

The results for Scenario 2, the heating system using Vacuum Tube panels with the air-to-water heat pump, are tabulated below where the electric consumption, solar thermal energy generation and the total energy demand vary depending on the city:

The electricity consumption (in kWh) represents the total electricity used by the heating system, which includes the air-to-water heat pump, backup boiler, and pumps. The solar thermal energy generated (in kWh) is the thermal energy generated by the vacuum tube panels for the heating system. The total system energy demand (in kWh) is the energy effectively consumed including the energy required for space heating and domestic hot water heating.

Analysis

The highest Solar Thermal Energy generation from the Vacuum Tubes in the above cases is from the case located in Calgary where 5,959 kWh is generated yearly. The highest kWh in and Total demand are for the case in St. Johns where we also see the lowest yearly thermal energy generation of 3,920 kWh.

The lowest energy demand for both systems is that of Kamloops, BC. The total energy demand in Kamloops for the system using Vacuum Tubes with the heat pump is lower than that of the system using photovoltaic panels with the heat pump.

The highest Solar Electrical Energy generation from the Photovoltaic panels is from the cases situated in Saskatoon where 2,716 kWh are generated yearly. The highest kWh in and total heating demand are for the case located in St. Johns where we also see the lowest yearly electrical energy generation of 1,935 kWh.

In a province like Alberta, where we see an average heating demand of 25,025 kWh in Calgary, and electricity costs are high (25.8 cents per kWh), the benefits of integrating solar energy become particularly clear. With the potential for significant solar generation—either 2,639 kWh of electrical energy or 5,959 kWh of thermal energy—it is highly advantageous to offset the electricity consumed by the heat pump when needed. Additionally, solar collectors offer a valuable backup solution during power outages, providing an alternative source of energy to ensure consistent heating and maintain comfort.

The highest electricity consumption for heating the house and providing sufficient domestic hot water in Scenario 1 and Scenario 2 occurs in Winnipeg (MB), with an annual demand of 16,885.5 kWh and 11,267 kWh, respectively. Since Manitoba has some of the lowest electricity rates among Canadian provinces and the second-highest solar thermal energy generation at 5,908 kWh per year, installing vacuum tube solar panels would be a logical choice. Additionally, the heating demand for both scenarios in Winnipeg is approximately average, with a demand of 25,245 kWh, compared to the other cities where these scenarios were tested.

Conclusion

From the above information we can see both systems offer a solid return on investment; the 5-ton air-to-water heat pump with the Vacuum tube panels or the 5-ton heat pump paired with the PV panels. The preference for either system would depend on energy costs and weather conditions in your region, the heating demand for space and the application for each system. To ensure you choose the most suitable and optimal system for your project, please reach out to our design team at the following email address: design@hydrosolar.ca or by filling out a design request.