How much battery storage does an average home need?

A typical European family using about 10–12 kWh/day needs roughly 13–14 kWh of nameplate storage for a grid-tied hybrid setup (one day/night cycle at 0.9 usable depth of discharge), or around 20 kWh if it wants to run off-grid with 1.5 days of autonomy. The exact figure depends entirely on your daily consumption and how long you want to run on stored energy. Our system designer computes it for your profile in two minutes.

How do I calculate my daily energy consumption in kWh?

Two ways. The bill method: take the kWh from your utility bill and divide monthly by 30 or annual by 365. The appliance method: for each device multiply its power in watts by hours of use per day, add them up and divide by 1,000. The bill method is fastest and gives a whole-home average; the appliance method is best for new builds or off-grid loads with no bill.

What is depth of discharge and why does it matter for sizing?

Depth of discharge (DoD) is the share of a battery's nameplate capacity you actually use. We size LiFePO4 storage to a usable 0.9 DoD — you plan to draw 90% and keep a reserve that protects battery health. Because of this, nameplate capacity is always larger than your usable target: divide the usable kWh you need by 0.9 to get the nameplate kWh you must buy.

How many batteries can I put on a wall?

Wall-mounted Storage Wall units are meant to be installed up to three in parallel on a wall, covering single enclosures up to about 14 kWh. Beyond roughly 15 kWh you should move to a floor-standing stacked tower, and past about 30 kWh to a 19-inch rack system. Do not try to hang a full tower of modules on a wall — form should follow capacity.

Do I need solar panels to have a home battery?

Not for a backup or hybrid battery — those can charge from the grid and discharge when you need them. Off-grid systems, however, always need a generation source, and solar is the usual choice. Adding solar to a hybrid or backup home simply cuts how much you draw from the grid. Array size depends on both your daily demand and your location's peak sun hours.

How is off-grid sizing different from backup sizing?

Off-grid systems must carry the whole house on stored energy for full days, so they are sized around days of autonomy — typically about 1.5 days so one cloudy day does not cause a blackout. Backup systems only need to bridge a grid outage for a set number of hours, so they are sized in hours (backup hours ÷ 24 of a day's load). The same house can therefore need four times more storage off-grid than it does for backup.

How much home battery storage do you actually need?

Ask ten households how big a battery they need and you get ten guesses. The honest answer is that storage size is not a feeling — it is arithmetic. Three numbers decide it, and once you have them the kWh almost falls out on its own.

This guide walks through the same method our engineering team built into the Senneon system designer. Read it to understand why the numbers land where they do; then let the designer do the sum for you.

Skip the math — our system designer sizes storage, inverter and solar for you in about two minutes. Enter your consumption and your goal, and it returns a complete indicative design.

The three factors that decide capacity

Every sound sizing comes down to three inputs:

Daily energy demand (kWh/day) — how much electricity your home actually uses in a day. This is the foundation; get it wrong and everything downstream is wrong.
How long you want to run on the battery — expressed as days of autonomy (off-grid) or backup hours (grid-tied). One cloudy evening is a very different number from three days off the grid.
Your scenario — off-grid, hybrid, or backup. The same house needs wildly different storage depending on whether the battery is the only source of power or just a buffer behind the grid.

Hold those three in mind. The rest of this guide is just how to pin each one down.

Step 1 — Estimate your daily energy use

There are two reliable ways to get your kWh/day.

The bill method (fastest)

Take your annual or monthly consumption straight from your utility bill and divide down:

Monthly kWh ÷ 30 = kWh/day
Annual kWh ÷ 365 = kWh/day

Typical European figures, to sanity-check yourself:

Household	Annual use	≈ kWh/day
1–2 people, apartment, no electric heat	~2,000–2,500 kWh	6–7
Family of 4, gas heating	~3,500–4,500 kWh	10–12
House with heat pump	~6,000–9,000 kWh	18–25
Heat pump and EV charging	10,000 kWh+	28–35+

The bill method gives you a whole-home average, which is exactly what you want for storage sizing.

The appliance-list method (most precise)

When you have no bill — a new build, an off-grid cabin, or a load you want to isolate — add up the appliances you will actually run:

energy (Wh) = power (W) × hours per day, then sum and divide by 1,000 for kWh.

A worked sample of common loads:

Refrigerator: 150 W × 8 h = 1.2 kWh
Freezer: 200 W × 8 h = 1.6 kWh
Lighting: 100 W × 5 h = 0.5 kWh
TV + computer: 200 W × 5 h = 1.0 kWh
Washing machine: 2,000 W × 1 h = 2.0 kWh
Dishwasher: 1,800 W × 1 h = 1.8 kWh
Electric oven: 2,500 W × 0.5 h = 1.25 kWh

That short list already reaches roughly 9–10 kWh/day — which is why a typical family lands where it does.

Step 2 — Turn demand into storage

Here is the core formula. It is the same one the designer runs:

Storage (kWh nameplate) = daily kWh × days of autonomy ÷ usable depth of discharge

Two things matter in that line:

Days of autonomy is how long the battery alone must carry the house. Off-grid systems typically plan for about 1.5 days so a single dull day does not black you out; a grid-tied hybrid only needs to bridge roughly one day/night cycle; a pure backup system is sized in hours (backup hours ÷ 24 = the fraction of a day).
Usable depth of discharge (DoD) is why nameplate capacity is bigger than what you draw. We size LiFePO4 storage to a usable 0.9 DoD — you plan to use 90% of nameplate and keep a floor for battery health. So you always divide your usable target by 0.9 to get the nameplate you must buy.

Worked example: a German family, off-grid

Daily use: 12 kWh/day
Goal: off-grid, 1.5 days of autonomy
Usable energy needed: 12 × 1.5 = 18 kWh usable
Nameplate: 18 ÷ 0.9 = 20 kWh

Twenty kilowatt-hours of nameplate storage. That is the answer, and it matches what the designer returns for that profile.

For contrast, the same 12 kWh/day house on a different goal:

Hybrid (bridge one day): 12 ÷ 0.9 ≈ 13.3 kWh → a single wall unit covers it.
Backup for 8 hours of the whole-home load: 12 × (8÷24) ÷ 0.9 ≈ 4.4 kWh → a small wall battery is enough.

Same house, same 12 kWh/day — three very different batteries. This is why the scenario matters as much as the consumption.

Don't want to run the numbers by hand? The Senneon system designer applies exactly this formula — daily kWh, autonomy, 0.9 DoD, your country's sun hours — and hands you a sized battery, inverter and array in two minutes.

Step 3 — Choose the battery form, not just the kWh

Storage is not one flat stack of wall boxes. As capacity grows, the sensible physical form changes — and putting too much on a wall is a real mistake:

Wall-mounted (small demand): the Storage Wall series covers single units up to ~14 kWh, and you can parallel up to three on a wall. Clean, quiet, ideal for apartments, backup and modest hybrid homes. Don't try to hang a whole tower on plasterboard.
Stacked tower (medium demand, ~15–30 kWh): past three wall units, move to a floor-standing stacked storage tower — 5.12 kWh modules on a base, scaling in steps. Our 20 kWh German example lands here: four modules on one tower.
19" rack (large demand, ~30–60 kWh): big off-grid homes and light-commercial loads belong in a rack storage system, and beyond that in parallel racks, engineered per project.

The rule of thumb: wall for small, tower for medium, rack for large. The designer picks the form a real installer would specify.

Step 4 — Match the inverter and solar

Storage capacity answers how much energy. The inverter answers how much power at once, and that is a separate question driven by your peak load — the largest simultaneous draw, including start-up surges. Motors and compressors are the trap here: a well pump can spike to five times its running watts on start-up, a fridge or air conditioner to three times. Size the inverter to the surge, not just the average, or it will trip when the pump kicks in. We build hybrid inverters in 5.5, 8 and 10 kW steps, with parallelling for larger peaks.

Solar then refills the battery. Array size depends on daily demand and your location's sun hours — a kilowatt-peak in southern Spain (~~4.5 peak sun hours/day) yields far more than the same panels in Germany (~~3.0). Off-grid systems always need a generation source; hybrid and backup homes add solar to cut grid draw. A complete off-grid solar system bundles panels, inverter, storage and balance-of-system so the pieces are matched from the start.

Common sizing mistakes

Over-sizing. Bigger is not automatically better. Storage you never cycle is capital sitting idle, and an oversized bank can cycle so shallowly it never earns its keep. Size to demand, then leave a sensible margin — not a fantasy one.
Ignoring surge. The single most common cause of a nuisance-tripping system is an inverter sized to average watts while a compressor or pump quietly demands three-to-five times that on start-up.
Forgetting the seasons. An annual-average sun-hour figure hides a hard truth: a German winter delivers a fraction of the summer yield. If you plan to run off-grid through December, size for the worst month, not the yearly mean — or keep the grid or a generator as backup.

The short version

Get your daily kWh, decide how long you want to run on it, and be honest about your scenario. Multiply demand by autonomy, divide by 0.9, and you have your nameplate kWh. Then choose the form — wall, tower or rack — and match an inverter to your surge and solar to your sun hours.

Or skip all of it: the Senneon system designer runs the same engineering, in your country, in two minutes, and returns a complete indicative design you can send straight to us for a quote.