Short answer
With a dynamic contract the price changes every hour. A battery that can respond to that charges in the cheap hours and supplies your house in the expensive hours. That can noticeably increase what a battery earns. The condition is that it happens automatically and that you can cope with the price fluctuations, even in a bad year.
Who this article is for Anyone considering a battery and wondering whether a dynamic contract goes with it.
What a dynamic contract is
The price you pay per kilowatt hour changes every hour and follows the wholesale price. At night and in the middle of the day electricity is often cheap; around dinner time expensive. In extreme situations the price can even be negative: then you get paid to take electricity.
What the battery does with it
A battery that knows the prices can:
- charge when it is cheap, often at night or in the middle of the day
- supply when it is expensive, usually between five and eight in the evening
- wait to charge from solar if prices are even lower later in the day
That happens automatically, based on the prices published the day before. You do not need to do anything; if you had to keep track of it manually, you would stop after two weeks.
What it gains you
The difference between the most expensive and the cheapest hour of a day is usually a few tens of cents per kilowatt hour. With a ten kilowatt hour battery running one cycle a day, that is an amount per day and not an amount per year that will make you rich. Added up over a year it certainly counts, and especially in winter, when your panels do little.
Important: this comes on top of what the battery does with your solar power, it does not replace it.
What to look out for
Can your battery do it? Not every brand can respond to prices. Some do it themselves, others via a service from the supplier or external control. Check before you buy.
Check this before you buy, not afterwards.
Cycle use. Every charge is one. More cycles per day means using up the warranty faster. Look at the number of cycles the manufacturer guarantees.
Your risk. A dynamic contract also means you feel an expensive winter. If you cannot cope well with that, a fixed contract is the better choice, even if the battery then earns a little less.
Feed-in still matters. What you use yourself is usually worth more than what you trade. See feed-in charges and the net metering scheme is ending.
What I would do
First choose the battery based on your solar power and your consumption; that is the basis. If it can also respond to prices, that is a bonus. Buying a battery purely to trade on prices is a different story, and then you want to do the sums properly first.
From my own work
Since the winter, a customer in Meerssen has been charging automatically between two and five at night and using that during the day when the sun is not delivering. In December and January, exactly the months when panels do little, he got the most out of it. In summer the battery simply does its normal job with solar power.
When to call an electrician
- You have a dynamic contract and want to know whether a battery can respond to it
- You want to know which brands do this well
- You are torn between fixed and dynamic
Which control is possible depends on the brand. See the packages.
Frequently asked questions
Do I need a dynamic contract for a home battery?
No. A battery works fine on a fixed contract with your own solar power. Dynamic is an extra, not a requirement.
Can every battery respond to prices?
No. Check with the brand before you buy; some do it themselves, others only via a service from the supplier.
Will my battery wear out faster if it charges more often?
Every cycle counts towards its lifespan. Look at the number of guaranteed cycles and take that into account when responding intensively to prices.
Further reading
The net metering scheme is ending: what changes for my panels
Your panels keep generating just as much. What changes is the value of the electricity you feed back.
Feed-in charges: why you pay for your own electricity
More and more suppliers charge for feeding your solar power back into the grid. Your bill shows what that costs you.
Solar panels and your consumer unit: what really needs to be done
What changes in the meter cupboard when panels go on your roof, when a PV distribution board is sensible and why your inverter cuts out on the very sunniest day.
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