Identify PV surplus
Set the amount of energy that can actually be stored.
Guide
Understand solar batteries: when does storage really pay off?
A battery is not automatically worthwhile just because it increases self-sufficiency. The key question is whether the extra self-consumption can realistically pay for the battery.
Quick answer
Does a solar battery pay off?
A battery is most interesting when there is evening demand and the PV system regularly creates daytime surplus.
Example
Example: Judge storage by the load profile
Start by clarifying whether a battery meaningfully improves self-consumption and economics. Then the comparison clarifies the effect of battery size, consumption, PV yield, electricity price and cycles and the boundary set by investment cost, lifetime, degradation and wrong sizing.
Decision focuswhether a battery meaningfully improves self-consumption and economics
Main leverbattery size, consumption, PV yield, electricity price and cycles
Separate checkinvestment cost, lifetime, degradation and wrong sizing
Next stepcompare added self-consumption with battery price and lifetime
How to read the resultDecision focus: whether a battery meaningfully improves self-consumption and economics. Separate check: investment cost, lifetime, degradation and wrong sizing.
Read the result together with battery size, consumption, PV yield, electricity price and cycles. Investment cost, lifetime, degradation and wrong sizing limit how directly you can act on it.
Decision view
Judge storage by the load profile
The overview separates result, lever and boundary: whether a battery meaningfully improves self-consumption and economics; battery size, consumption, PV yield, electricity price and cycles; investment cost, lifetime, degradation and wrong sizing. For Understand solar batteries, this shows which value carries the statement and where the model ends.
What the visual shows
The values explain the most important parts of the visual.
Resultwhether a battery meaningfully improves self-consumption and economics
Main leverbattery size, consumption, PV yield, electricity price and cycles
Separate checkinvestment cost, lifetime, degradation and wrong sizing
The practical benefit becomes clear only when battery size, consumption, PV yield, electricity price and cycles are realistic and investment cost, lifetime, degradation and wrong sizing are checked separately.
Load profile, weather, storage losses and tariff assumptions can change the economics. Investment cost, lifetime, degradation and wrong sizing can change the real-world result and should be reviewed separately before binding decisions.
How it is calculated · Mathematical background
How it is calculated
The method separates numerical core and decision frame. battery size, consumption, PV yield, electricity price and cycles shape the result; investment cost, lifetime, degradation and wrong sizing mark the limit.
Account for losses
Not every charged kWh returns fully later.
Calculate added value
Stored power replaces grid electricity and raises self-consumption.
Include battery cost
Purchase price, lifetime and possible replacement matter.
Compare payback
Added cost is compared with the additional value.
Separate independence
More autonomy is useful, but not automatically a return.
The calculation describes: whether a battery meaningfully improves self-consumption and economics. The range comes from battery size, consumption, PV yield, electricity price and cycles; the limit comes from investment cost, lifetime, degradation and wrong sizing.
Detailed calculation explanation
A battery shifts solar electricity over time: daytime surplus can be used later. Simplified: battery value = additional self-used kWh × avoided grid price − losses and extra costs. Battery payback should be checked separately from the PV system so autonomy is not confused with return.
If-then rules
If-then rules for the decision
When usage or prices can change
battery size, consumption, PV yield, electricity price and cycles define the range. The cautious case should reflect the assumption most uncertain in real life.
When choosing technology or tariffs
investment cost, lifetime, degradation and wrong sizing belong beside the result. That keeps the calculated statement separate from the open points.
When planning the next step
The next step follows from whether a battery meaningfully improves self-consumption and economics, but only together with battery size, consumption, PV yield, electricity price and cycles and investment cost, lifetime, degradation and wrong sizing.
Step by step
How to interpret this topic
Read demand and generation
Question: whether a battery meaningfully improves self-consumption and economics. The value becomes useful when investment cost, lifetime, degradation and wrong sizing remain visible as the frame.
Find the strongest energy lever
The strongest influence is battery size, consumption, PV yield, electricity price and cycles. These inputs show which assumption moves the result most.
Keep model limits realistic
The frame of the statement is investment cost, lifetime, degradation and wrong sizing. These points are not part of the final value; they limit how it can be used.
Plan the next energy step
Next, the scenario has to keep result, battery size, consumption, PV yield, electricity price and cycles and investment cost, lifetime, degradation and wrong sizing plausible at the same time.
Checklist
Quick decision check
- Define the starting question: whether a battery meaningfully improves self-consumption and economics.
- Vary the main lever within the same scenario: battery size, consumption, PV yield, electricity price and cycles.
- Keep the boundary separate: investment cost, lifetime, degradation and wrong sizing.
- Compare base case and cautious case only with the same reference value: whether a battery meaningfully improves self-consumption and economics.
- Turn the result into action only when battery size, consumption, PV yield, electricity price and cycles and investment cost, lifetime, degradation and wrong sizing remain plausible together.
Common mistakes
Common decision mistakes
solar batteries: reading the result without context
Without a clear starting question, it remains open whether a battery meaningfully improves self-consumption and economics. The reference value belongs next to the result.
solar batteries: setting the main lever too optimistically
Overly favourable assumptions for battery size, consumption, PV yield, electricity price and cycles make the result look more stable than it may be later.
solar batteries: overlooking the model boundary
investment cost, lifetime, degradation and wrong sizing sit outside the core calculation and should be settled before binding steps.
FAQ
Frequently asked questions
Is a solar battery always useful?
A cautious counter-case shows whether battery size, consumption, PV yield, electricity price and cycles leave enough margin.
Which metric matters most?
The tipping value matters: once battery size, consumption, PV yield, electricity price and cycles reverse the statement, margin decides.
Can a battery make sense even if it does not pay off?
The calculator alone is not enough for a binding decision; investment cost, lifetime, degradation and wrong sizing remain outside the calculation.