Which Solar and Battery design is best for you?

We are often asked what solar system should I install? Do I need battery storage and if so how much? I am buying an EV, how will that change my requirements?

As mentioned in previous blogs, the technology behind energy systems is continuously changing. This means that designing energy solutions is becoming even more complex.

Installers are supposed to produce a report indicating the estimated energy that a system design would produce. This report will usually compare typical household consumption against generation data to indicate a return on investment (ROI). However these reports are becoming less accurate as technology develops and more importantly, as a household’s energy consumption changes (especially when you purchase an EV). If you are prepared to make some behavioural changes then return on investment can be improved. So this blog post will provide some insight into how we design solutions at Tewdric Energy.

When we start looking at the hardware there is a tendency for equipment suppliers to build ‘hybrid or all-in-one’ devices. For instance manufacturers will combine a battery and inverter into one box or an inverter and EV charger into one box. Some manufacturers equipment will not inter-operate with other manufacturers products. This should be considered carefully. For instance if an integrated inverter fails it can be a costly fix whereas replacing a stand-a-lone inverter may be cheaper. But some ‘all-in-one’ devices can offer considerable cost savings. Single vendor products could limit flexibility. It is often better to select ‘best of breed’ equipment and ensure they interoperate. This is one of many aspects of design that we will consider.

Probably one of the most important aspects when it comes to modern energy system design is the consideration around how flexible and how good the supporting the software is. Most equipment will require a software app to enable proper use. This is where we believe most development will be made over the next few years. Most if not all settings for the hardware will be made via the app. At a very basic level the software should allow changes to scheduling of events such as when a battery should charge/discharge and when an EV should start charging etc. We would also strongly advise that any equipment is capable of supporting third party communication especially with an Application Programming Interface (more commonly known as an API). This allows third parties to communicate with the hardware, for instance this will allow an energy company to start charging your EV when the cost of energy is at its lowest. But future usage will require multiple changes in configuration and therefore on-going software support is essential. Long gone are the days of installing some solar panels and then walking away.

We would normally recommend maximising generation capacity. That does not mean maximise generation at any cost but simply maximise generation based upon cost effective equipment. If you don’t have a large roof for instance you will want to maximise your generation to cover as much of your household usage. We would highly recommend good solar panels that have minimal degradation, good efficiency and don’t cost the earth to install. Some may have an aesthetic issue and want to use solar slates or similar. If this is very important to you then that is OK but be aware that you are probably paying up to four or five times as much for the same solar generation as traditional panels. Therefore some of the aesthetic solutions have a very long return on investment. But obviously the environmental benefits are still there.

In addition we would normally suggest using optimisers with solar panels, unless you have the luxury of absolutely no risk of shading from nearby structures or trees etc. Optimisers will help maximise the efficiency of your solar generation without a huge cost increase. Optimisers will also supply generation data per panel. This helps monitor the performance of your energy generation as well as help identify any particular problems down to the individual panel.

A good quality inverter is essential. The inverter coverts the DC power the solar panels produce into AC power that your home will consume. The efficiency of this conversion process can have a big impact on the amount of useable electricity your system produces. You may have a combined inverter that will allow the DC solar power to charge a battery storage unit directly and will then convert the DC power from the battery to AC power. You may opt for separate inverters which can have benefits such as supplying backup power when grid power fails. Some inverters will have a few years warranty and others have long 20 year+ warranties. Replacing inverters can be costly therefore having a reliable inverter is important. You may save money in the short term but it will lead to higher maintenance costs and less energy generation in the long run. When we mentioned reports earlier we should point out that most do not consider on-going maintenance costs or the reliability of the original system design, they assume 100% reliability. Some installers make a very nice living out of repairing/maintaining systems.

One of the newest pieces of equipment that has made its way into prominence over the last few years is battery storage. Most solar systems installed as recently as 2020 didn’t include battery storage. Many reports say that adding battery storage to an existing solar system will increase self-consumption from 30-50% to 80% which means that 80% of the energy that is generated by the solar panels will be used by the home and less than 20% will need to be exported to the grid. When looking at battery storage you should always ensure you install a modular system i.e. the system is capable of expansion with little or no additional cost other than simply adding another battery storage module. In fairness most battery storage manufacturers provide this. However the quality of the battery storage is very important. The difference here can mean you could be replacing your battery after five years instead of 10. Most manufacturers will quote values for depth of discharge and number of cycles. The battery management units should prevent a battery from being charged too much and prevent the battery from being drained too much. With current technology a battery should avoid using more than 80% of its total capacity and should not be drained 100%. Some manufacturers will quote total battery capacity but in the real world, in order to maximise the life of the battery, that capacity may not be accessible or will require an override (where a user will accept that the life of the battery will be reduced). However as modular systems make expansion easier I would suggest installing a quality battery and expand the storage as the requirements demand. Over specifying storage at the beginning of a project can be costly and a battery that isn’t used will still deteriorate over time.

Batteries are still a new development and possibly will have the biggest impact on financial returns in the future. We will save the discussion about energy trading for a future blog.

If you have an Electric Vehicle (EV) or are thinking of purchasing one you may have or be considering an EV charger. At the moment there isn’t much between the various chargers that are on the market. Most chargers have software that can schedule charging etc and some can work with energy providers which will let them decide when to charge your vehicle. The EV’s themselves also have their own software and it is important that an EV works with your charger, that is obviously the most important feature. Some solar inverter manufacturers combine an EV charger which allows the output from solar panels to directly charge an EV. This is very efficient but only works when you have the vehicle connected at the same time as excess solar power is being generated i.e. daytime.

We consider most of the current chargers as first generation chargers and over the next few years we believe there will be a lot of development in this area. We have to declare at this point that Tewdric Energy is designing a next generation charger. We currently offer a commercial charger for business which is already designed to support some important features. We suspect like other manufacturers we are also designing a second generation charger for domestic use that will support features such as vehicle to grid. This feature will allow an EV to essentially act as battery storage for your home or business. This will really help in situations where energy companies pay for power to be exported to the grid and/or reduce consumption at peak periods. For now though we ensure that an EV charger works with the vehicle you have.

So in summary when designing a solution we would suggest the maximum number of good quality solar panels that you can fit, with optimisers plus an efficient inverter with decent warranty. We highly recommend a modular battery that fits with your current consumption. This will allow for future expansion. Finally when selecting an installer we would make sure that you select an installer that is going to be able to offer the post sale customer support especially one that understands the importance of the communications and software that is constantly being updated.

Finally if you select a good system you should get a great return on your investment, but you will also be doing your bit for the planet. We are big on energy independence and this is a great way to line your own pocket as opposed to the big bad fossil fuel energy companies.