Given the rapidly rising cost of energy it goes without saying that we all would realistically like an energy efficient home and if there was a chance to get some energy for free then that seems to be a complete no brainer. So, is this a pipe dream or is there a route to this golden goal?
The solution is electricity. Electricity can be generated from many sources, stored and then turned into energy or heat. To generate our own electricity we can install solar photovoltaic (PV) panels on the roof and then also install an electric heating system to keep us warm. The most efficient electric heating systems are heat pumps.
In this guide, renewables and ventilation installer David Hilton explains the pros and cons of using heat pumps and solar panels in tandem to provide your home with its energy requirements.
Are solar panels and heat pumps a good combination?
In terms of solar photovoltaic, the average home with a standard single phase electric supply can fit 4kWp to the home (around 10 panels) without any special permission. Depending where you are in the country, a south facing 4kWp array would generate around 3000 to 4000 kWh per year.
And how about heat pumps? For every one kW of electricity that a heat pump uses, it delivers around three or four kW of heat. It does this by using the refrigeration cycle to move heat rather than create heat. So, as an example, an air source heat pump will move heat from the air around it to the central heating system in the home.
The combination of PV and heat pumps seems ideal — almost like perfection. But there is a problem. The time of year when we generate the most electricity is summer and this is not the time of year when we need the most heat.
Adding a battery to the PV system will help a bit by allowing you to store the energy you generate during the day, perhaps when you are at work, and use it at night, but unfortunately we cannot realistically have enough batteries to charge up in summer and use in winter.
We therefore ideally still need the grid and the PV panels are, at best, direct power for smaller energy use such as fridges, TV and lights but for the heat pump they are an offset.
Can you power a heat pump using solar panels?
If you have enough PV panels you may be able to generate enough electricity annually to power your heat pump but you will not realistically be able to completely use it directly.
The yield in July is around six times more than it is in January. Because the solar PV panels are wired back to your main electrical distribution box (consumer unit), all the energy you generate will be used by the home first. The heat pump is also wired back to this board so if it is running it will use the generation. Smart controls can sometimes turn things on when they detect excess energy or the battery can also store excess generation. The PV panels would need to be generating a lot, close to their maximum, to completely power a heat pump.
Can you benefit from SEG when you have both technologies?
We used to get paid a very generous incentive (Feed In Tariff) for generating electricity but that is no longer the case. There is, however, the Smart Export Guarantee (SEG) which is a payment by most energy suppliers for any excess electricity that you export from your PV system.
It is up to the energy company to set the tariff they pay you so do shop around. It is also not very generous when compared with the cost we pay to import energy, so it is always better to try and use the energy and only export it as a last resort. If you have an electric vehicle then much more of the generation can be put into the vehicle if it is there.
The SEG will also vary according to what electric tariff you are on. A heat pump should not affect your ability to claim SEG payments but there may be some electricity tariffs that are better suited to electric vehicles or heat pump use and it may be worth sacrificing a few pence on the SEG to secure a lower rate for the car or the heat pump, depending on which one uses the most energy. Do your homework and do the maths.
How do you make the most of solar panels and a heat pump on a home?
In a modern home we are moving towards electricity as the go to solution for heating, vehicles, cooking, work and recreation. It therefore makes sense to generate as much as we feasibly can and then manage it to use as much of the generation as we can.
PV and heat pumps are here to stay and they will be completely ‘normal’ products in the very near future. It is up to us as homeowners to adapt our routines to be able to use free energy when it is available and optimise our heating systems either with smart Apps or by mapping the heating schedules to our lifestyles.
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David is a renewables and ventilation installer, with over 35 years experience, and is a long-standing contributor to Homebuilding and Renovating magazine. He is a member of the Gas Safe Register, has a Masters degree in Sustainable Architecture, and is an authority in sustainable building and energy efficiency, with extensive knowledge in building fabrics, heat recovery ventilation, renewables, and also conventional heating systems. He is also a speaker at the Homebuilding & Renovating Show.
Passionate about healthy, efficient homes, he is director of Heat and Energy Ltd. He works with architects, builders, self builders and renovators, and designs and project manages the installation of ventilation and heating systems to achieve the most energy efficient and cost effective outcome for every home.