[CPercy]

Looking at getting some solar panels fitted to our three bed semi-detached. Is it best to get a battery fitted at the same time or is it more cost-effective just to sell any excess electricity back to the national grid?

Many thanks in advance,

Caroline

[chptr2archt]

Hi Caroline,

I wrote this answer to a similar query, but should also help you I hope:

It is important to consider not just the panels but the tariff and way you’ll use it. PV panels without a battery means you either use what you produce (‘live’) or export any excess back to the grid. With a battery you can use what you produce now, or use it later having stored it up. This requires a behavioural change to say run appliances in the afternoon or evening once the battery has charged. Once your battery is full and you’re producing more energy than you can used, you can then start to export and earn money back.

We find that April is the flip-over month from when we start to equalise what we produce off the roof and what we buy/sell. Before April, with little sunshine, you buy in more than you produce, April is even, and after April we are selling more than we use. Therefore it is important you have a good export tariff to make use of this. Octopus, for example offers 15p per kWh (you buy for c. 25p). Alternative tariffs are better suited to running an EV by offering cheaper overnight tariffs, or even flexible ones where you can buy or sell throughout the day.

If you use a lot of hot water and your tank is compatible you can include a solar diverter which sends excess energy created into your hot water tank, reducing the burden on your (assumed) gas boiler.

So there are lots of variables like occupancy, whether you work from home, require lots of hot water.

Ultimately a battery gives you control of how you use your energy and means you can use the energy you’ve produced cheaply even at peak times. You will need the physical space for one but once set up the way you want it, they don’t take any time or knowledge to run in the background.

Alex

[Liana]

Hi Laura,

It all comes down to what your annual electricity consumption is and the size of your PV system.  These details can be found on your electricity bill as estimated annual consumption, whether you have any  high consuming items such as an electric vehicle or ASHP (Air Source Heat Pump) as examples as these are thirsty appliances requiring a lot of energy to run off of over a 12 month period and monthly period.

If your system generates less than you are consuming, then you wont need a battery eg, if your energy consumption is 4000kw per year, but your pv system allows for 3000kw per year, then you will still be paying for the extra 1000kw of energy, and unlikely to be storing any excess energy into a battery or exporting it.  However if your energy consumption is less than what the PV system allows for once you have taken all things into consideration, then it is worth it to have battery storage, this is especially useful given when the sun goes down in the evenings, instead of going back to the grid and being charged for this energy, you will instead use the stored energy from your battery to power your home.  Many batteries allow for a depth of discharge to 90% so there always needs to be 10% left in the battery at all times.  There are one or two brands, one in particular that allows full depth of discharge which is GivEnergy, a personal favourite brand of mine.

Your system if will be operating at peak performance during the summer months and this is where you are most likely to have excess energy to sell back to the grid on the assumption that your system provides an output greater than your household energy usage.

Octopus energy has the best feed in tariffs for selling energy back to the grid, so if you go down the battery storage route, give them a call to determine the best tariff for you.  You could also consider an AC Coupled system if you were a high consuming household, as you could then use the AC Coupled battery to charge on off peak rates fully during the night which would be cheaper than paying full rate tariffs, esp in winter when we have so little daylight in comparison.

There isnt a slam dunk answer as every household is different and unique in its own right.

I hope this helps.

Warmest wishes

Liana

• This reply was modified 2 years, 1 month ago by Liana.
• This reply was modified 2 years, 1 month ago by Liana.

[Ellen Oliver]

Hey Liana,

How are you getting on with your solar journey? Just to let you know we’ve recently written a blog post with everything you need to know about solar battery storage – https://forum.retrofitwest.co.uk/benefits-of-battery-storage-for-solar-panels/

Let us know any questions or comments! All the best,

Ellen

[Energy Chap]

I don’t really treat my batteries as an add on to my solar, but the solar as an add on to the batteries. We are on a smart tariff that offers 7p/kWh for 6 hours overnight. So we charge the batteries up fully each night. Then the solar mainly exports or tops up the batteries a bit in the day. I do this option at the moment because we get 15p/kWh for what we export. If the figures change then I will change that approach.

Batteries do give the freedom to look at more smart tariffs though. If you get a smaller one that is only big enough to cover your 4pm-7pm consumption then you can look at the Agile tariffs and avoid their really high peak rates and look to charge by PV or on the cheaper night rates. If you have an Electric Vehicle then you can take advantage of the pretty low cost off peak rates. Or Tomato Energy do a tariff (at time of writing) offering 5p/kWh for 5/6 hours overnight.

Every home is different and times change, but I’m no longer a fan of diverters to immersion heaters where the export payment can be better value.

[Author]

Posts