How to choose your renewable energy sources

Installing solar PV panels. (CC0)

You know you want your new dream home to include some green energy generation, so you can be more independent, save money in the long term, and do your bit for the planet. But how do you know what’s right for you?

There’s so many factors at work in choosing the best renewable energy system for your site and budget. It’s an important decision which will impact you and your home for years, so you’ll need to do a lot of research on the particular system you choose - but it’s good to start broad and get more specific later. We’re here to help you determine which type of renewable energy is right for you.

Wind, water or sun? Or something else? We’ll run through the most popular types of domestic renewable energy and point out the key limitations and benefits of each.

But first, a word about efficiency

It may not be as exciting as sparkly new cleantech, but improving the energy efficiency of your home is both cheaper and greener than generating your own clean power. Starting with the latter is like mopping the floor without turning the taps off. What’s more, heat pumps will be useless unless your home is already air-tight and well insulated. Take a look at our previous post about optimising energy efficiency and get your usage down as much as possible before going on to generate what you do need from clean sources.

If you have maximised your gains from efficiency, then let’s dive in to the renewables…

Solar PV

Short for solar photovoltaics, solar PV means solar panels that convert the sun’s energy into electricity (as opposed to hot water, see below). This is probably the most well-known and commonly used form of renewable energy. You’ll need a suitable roof, which ideally faces south (or at least not north, that’s the worst orientation for the northern hemisphere) and isn’t too heavily shaded by near-by buildings. The latter can sometimes be a problem in urban centres. Flat and pitched roofs are both suitable, as long as the pitch isn’t extremely steep.

Oakdene Passiv House, one of our projects with solar PV panels

Solar thermal

In contrast to solar PV, solar thermal panels use the sun’s heat to warm up water, so only provides for your hot water (or central heating if you have radiators) not other energy. You’ll need a suitable roof with the same caveats as solar PV. Apart from the hot water vs electricity, the other key difference is solar thermal is much more affordable and has a much shorter payback period.

Wind

One of the most common renewable technologies along with solar, wind turbines transform the wind’s kinetic energy into electricity. It’s not very popular for the domestic scale, as most properties are not suitable due to lack of wind, lack of space and planning restrictions. But if you have a rural home in a windy area, ideally up a hill, then it could be perfect for you. Wind works particularly well in combination with solar as the weather usually favours one or the other.

Micro win turbine on Baden Powell Lodge, generating up to 1.25 kW (CC Peter Facey)

Hydro

Like wind, hydro power is a powerful technology for large scale generation based on a kinetic turbine, but is rare for domestic scale as you need a stream or river. A lake can also work, if there’s two sections at different heights for the water to flow down. A small hydro system would work well for a rural water-side home.

Heat pumps

Ground, air or water heat pumps extract thermal energy from outside - even in temperatures as low as -15C - and use it for your central heating and/or hot water system. Ground source heat pumps need a large area to dig a trench and bury a coil system underground, so only work if you have a large garden. Alternatively, you can dig a deep vertical borehole, which is compact but expensive. Air source heat pumps are compact and more affordable, but they’re less efficient and the system sits on the exterior of your house which can look unsightly. Water source heat pumps are less common because you obviously need a body of water beside your property. All heat pumps produce low-grade heat, so to be effective you need to have a very energy-efficient home and leave them running all winter.

Biomass

One of the oldest forms of renewable energy, biomass burns wood logs, pellets or chips to produce warmth and heat water. A stove just heats one room and adds a cosy ambiance, or can be fitted with a back-boiler to provide hot water. Alternatively a full biomass boiler replaces a gas or oil boiler and fires the whole central heating system and hot water. It does emit some emissions, but only the carbon that the trees absorbed while growing - so it’s carbon neutral. Some extra carbon comes from processing and transporting the fuel, but if you source it locally this will be minimal. The main limitation is space: a biomass boiler is reasonably bulky and you also need space to store the fuel close to the boiler and also close to a delivery point. If you have a garage then it could be ideal.

What kind of property do you have?

The main limitation is how much space you have, but your orientation and weather is important too. In some cases planning can be an issue, for example if your property is Listed then planners may only let you have solar panels on the back of the property - which may not be south facing. But none of these renewable technologies - barring wind - should be a problem in conservation areas.

- Urban terraced townhouse - try solar thermal, solar PV, air source heat pump
- Suburban semi-detached with large garden - try biomass, ground source heat pump
- Detached rural farmhouse - try solar, wind, hydro