The short answer is yes, solar PV panels can power your heat pump and cut your total energy bills in half when combined with time-of-use tariffs. In this guide we introduce you to the power of solar, smart tariffs and batteries and why they’re such a great match for heat pump homes.

Contents

1. Introduction to solar electricity
2. How does solar power my heat pump?
3. Who should fit solar?
4. Things to consider when fitting solar
5. Who should fit a battery?
6. Ready to make a start?

1) Introduction to solar electricity

At a basic level, solar PV panels take the sun’s energy and convert it into electricity for your home. Solar is one of the most accessible renewable technologies available to households with minimum disruption and quick paybacks. For many households solar panels are a great place to start your home decarbonisation journey.

2) How does solar power my heat pump?

When you move away from a gas or oil boiler to a heat pump you can use your solar panels to power your home and your heating system.

Powering your heating

In the early and late winter months, when the sun is shining but it's cold enough to put your heating on, solar panels will create a surplus of electricity that you can use to run your heat pump. It will not cover all of your heating demand, but it will cover some.

It's important to run your heat pump during the day to make use of the available solar electricity. Even if you’re not at home, the house will retain its heat for some hours.

Heat pump households can take advantage of flexible tariffs that are lower at off-peak times (eg 4am-7am) and more expensive at peak times (eg 4pm-7pm). Running your heating during off-peak periods and using solar when it’s available to power your heat pump during the day will cut your energy costs further.

It is important to set the heat pump up to operate outside of the peak-time tariff windows to minimise costs, otherwise no special equipment is needed.

Powering your hot water

In the summer the panels can provide all of your hot water. You need to set your hot water to come on during the day when the solar is at maximum output. Heat pump cylinders are larger which means you can store enough solar-powered hot water for 24 hours.

In terms of equipment, you can either use a special hot water diverter to direct the solar energy to the hot water cylinder, or use the heat pump to power the cylinder. Using the heat pump will mean it will run in the day time which may not be desirable if it's located in the back garden.

3) Who should fit solar?

Anyone that has a roof facing South, East or West (and any orientation in between) and can accommodate at least six panels should fit solar PV panels. A south facing roof will be where your home gets the most sun and this might be the front of your property.

4) Things to consider when fitting solar

We guide you on the optimum number of panels, how much electricity they provide, solar tariffs, costs and inverters.

How many panels should I fit?

Our blanket advice, subject to a more detailed analysis, is to fit as many as possible. If you have a huge roof then as many as your District Network Operator (DNO) will allow. (Your DNO is responsible for electricity meters and supply.)

In short, the bigger the array, the quicker the installation will payback, as you will increase how much you can use directly and receive a healthy sum for everything you export back to the grid.

How much energy do they provide?

An average installation will comprise an 8-10 panel array. This will produce around 3,000-4,000kWh per year depending on roof angle and direction of the roof (e.g. a south facing roof will generate more electricity than a west facing roof), and where you are in the country (Scottish readers will be at the lower end of that range). You can typically increase to 15-16 panels to maximise your investment if you’re lucky enough to have enough roof space (e.g. fitting panels on both East & West facing roofs).

The average household will use around 3,000kWh of electricity in a year and an 8-10 panel array would provide about 50% and 50% would be sent back to the grid. A typical heat pump installation will add another 3,000kWh and soak up another 25% or so of surplus energy from the solar array.

How much does solar cost?

Prices vary depending on the number of panels. A 6-panel array will cost around £4,500 while a 14-panel array will cost around £9,500 (this is excluding the cost of a battery).

Households can typically expect to recoup the upfront cost in 6-9 years depending on how much you can consume directly and interest free finance is making it easier than ever to afford.

Are some panels better than others?

The short answer is no, modern 400 watt panels are all technically similar. The key technology to get right is the inverter.

Which tariffs should I consider?

An increasing number of electricity providers offer solar export tariffs, where they pay you for the electricity you export, typically up to 15p per kWh. You need a smart meter to take advantage of these export tariffs. Note, you can often use a different energy supplier to export your electricity, so shop around for the best export rate. Top export tariffs are available from Octopus, Ovo and Good Energy.

What else do I need to know?

Solar panels need an inverter to convert energy from the solar panels into usable electricity for your home. It is a fairly unobtrusive white box, about the size of a carry-on suitcase, that hangs on the wall, and needs to be as close as possible to the Solar panels..

There are a couple of different types of inverter to consider and the best one for you will depend on when you’re at home.

If you’re at home in the daytime:

A standard ‘grid-tied’ inverter will let you use electricity as it is generated. If you are at home during the day your demand is greater and you can use a greater percentage of the electricity as it is generated.

If you’re out most of the day:

A hybrid inverter might be best for you as it enables you to easily add batteries to your installation, now or in the future. If you’re out most of the day, you will use a smaller percentage of available electricity and a hybrid inverter will help you store surplus electricity for when you get home. However there are other ways of using surplus electricity (eg. if you have an EV) that means a battery is not necessary (see Introduction to batteries section below).

If you have some shading:

Historically ‘micro inverters’ were used to counteract shading on solar panels, as they enabled each panel to work individually, i.e. if a few panels were not generating electricity, they didn’t affect the rest of the panels.

Today, ‘optimisers’ can be added to panels at the time of installation to minimise inefficiencies from shading. They are easy to fit and the small price increase per panel is paid back in the overall ‘optimised’ generation.

If you live in a protected area or property:

Fitting solar panels in conservation areas, areas of outstanding natural beauty and listed buildings can all require planning consent, however local authorities often have their criteria listed on their websites to assist in applicants. Limitations tend to be based around minimising visible changes to the exterior of the property and its surrounding area.

5) Introduction to batteries

Batteries are fast becoming the third part of every solar installation, due to rapidly falling costs. Batteries help to capture the surplus electricity from your solar array by storing it for later when the sun has stopped shining.

Who should get a battery?

This is a really tricky question because it depends on the size of your solar array, your heating system, if you’re home in the day and whether you have (or plan to have) an electric vehicle (EV).

If you have a gas boiler: a battery is an excellent option for households that haven’t yet transitioned to a heat pump and don’t have any other way of utilising the surplus electricity.

If you have a heat pump: a heat pump will use some of your surplus electricity during the milder winter months and your hot water cylinder will soak up a lot during the summer. If you’re not at home during the day a battery may be beneficial, but you can also consider timing appliances to work when you’re out, for example the dishwasher and washing machine.

If you have an EV: you may be able to use your car’s battery to soak up a lot of the surplus all year round, and newer models coming onto the market will be starting to offer V2H charging (vehicle to home), where you can power your home with your car battery. A home battery is less useful in this scenario.

If you’re on a budget: we recommend you fit solar PV and de-prioritise a battery. You will still be paid for any electricity you send back to the grid.

Does charging up on off-peak tariffs pay off?

Charging the battery overnight on low, off-peak tariffs can reduce your overall electricity bill providing you minimise electricity use during peak periods when the cost of electricity is much higher. Batteries can still have a longer payback period than solar PV panels, but they do reduce your carbon footprint further,

What size battery do I need?

Another tricky question, but in general it's related to the size of the solar array and whether you can use the surplus.

If you have a large solar array and no other ways of utilising the surplus electricity, go with a larger battery.

If you have a small solar array or a large array with other storage options (hot water cylinder and/or EV) go with a smaller battery or no battery.

Consider waiting a year: it’s often worth waiting to see how much electricity you send back to the grid and adding a battery later if it's significant. As standalone batteries now attract 0% VAT, so there is no cost downside to waiting 12 months.

6) Ready to make a start?