How big a home battery do you need for Ukraine's winter outages? Sizing for 2026/27

To size a battery for winter outages, add up the average draw of the appliances you need during an outage, multiply by the hours without power, then allow for losses and depth of discharge. For a house with a gas boiler, router, lights and fridge that is about 3.4 kWh for a 12-hour outage, so one 5 kWh module; for three days off-grid it is about 25 kWh. Inverter power is a separate question: it decides what can run at the same time.

Below is the calculation step by step, using SolarPlan's model and official sources, as checked on 7 October 2026.

What can Ukrainian households expect in winter 2026/27?

Nobody can forecast outages precisely: they depend on attacks on the grid, weather, imports and repairs. What is known: on 6 and 7 October 2026 Ukrenergo, the transmission system operator, applied hourly outage schedules in some regions, of 0.5 to 1.5 queues, citing the consequences of Russian missile and drone attacks.

For the winter itself there are only expert views. Yuriy Korolchuk, co-founder of the Institute of Energy Strategies, told UNIAN in August 2026 that his baseline scenario is twelve hours with power and twelve without, and his pessimistic one is whole days without power during emergency repairs. That is an expert opinion, not an official forecast, so it makes sense to plan for several scenarios:

• a 12-on/12-off schedule, where the battery recharges every half day;
• a full day without power after an attack;
• several days off-grid after serious damage to the local network.

The current schedule for your address is published by your distribution system operator (oblenergo).

Capacity or power: what are you sizing?

A backup system has two separate ratings that are often confused.

• Battery capacity (kWh) is how much energy is stored. It decides how long your appliances run.
• Inverter power (kW) is how much load it carries at once. It decides what can run together.

A fridge draws 100–200 W while running but 600–1,200 W when its compressor starts, and a boiler pump takes 3–5 times its rating at start-up (figures from the Ukrainian kit seller Keyvolt, May 2026). The inverter must ride through these peaks, or the system trips exactly when the compressor kicks in.

Which appliances to keep on, and what do they use?

SolarPlan's model, used in the backup power plan, assumes these values over an outage (averages allow for the fridge compressor running only part of the time and lights not being on all day):

These are typical values, not measurements of your devices. To be more precise, take the fridge's yearly consumption from its energy label (kWh/annum) and divide by 365, and look up the boiler's electrical power in its manual. Check the manual too for what the manufacturer requires when the boiler runs from an inverter.

Note the last row: a single electric hob uses almost as much as everything else together and needs an inverter of 2 kW or more. Cook while the grid is on.

The sizing formula

1. Add up the average power of the appliances you need (W).
2. Multiply by the hours without power: that is the energy delivered to the appliances (Wh).
3. Allow for inverter losses: SolarPlan's model divides by √0.9 ≈ 0.95 (a round-trip efficiency of about 90% for LiFePO4).
4. Divide by the usable depth of discharge. For LiFePO4 it is usually 90%: Deye, for instance, recommends a 90% depth of discharge for its SE-G5.1 Pro-B module.
5. Round up to a size that is sold (5 kWh modules, power stations in 0.5–1 kWh steps).

Worked example: a house with a gas boiler

Router and lights, fridge, boiler with pump, laptop and phones: 50 + 60 + 110 + 60 = 280 W on average, or 6.7 kWh a day.

Checking it the other way: a 5.12 kWh module delivers about 4.4 kWh to the appliances, roughly 15–16 hours at 280 W. Two modules give about 31 hours.

Inverter. Everything running at once is 470 W, about 0.6 kW with a 25% margin, and the fridge has the biggest start-up surge. For the essentials alone a 1 kW inverter with a twofold short surge rating would do. If you also want a water heater, washing machine or kettle, you need a 3–5 kW hybrid inverter. A bigger inverter does not add hours: it lets more run at once and drains the battery faster.

Will it recharge in time? On a 12/12 schedule about 3.5–4 kWh has to go back in during 12 hours with power, which any hybrid inverter manages. With shorter windows (say 4 hours) the charging power matters: Deye gives a recommended charge/discharge current of 50 A for its 51.2 V module, about 2.5 kW per module.

Ready-made house configurations with prices are on the pages for a 10 kW system with backup and a 10 kWh battery.

Worked example: an apartment

A flat on district heating has no boiler, so the usual set is router and lights, fridge, laptop and phones: 50 + 60 + 60 = 170 W on average.

The simplest option for a flat is a portable power station that plugs into a socket and needs no installation. Station makers estimate runtime as capacity × 0.85 ÷ the load. So:

• 4-hour outages: 0.68 kWh ÷ 0.85 ≈ 0.8 kWh → a 1 kWh station (about 27,500–48,500 UAH on hotline.ua on 6 October 2026);
• 12 hours: 2.04 kWh ÷ 0.85 ≈ 2.4 kWh → a 2.5–3 kWh station (3 kWh models about 74,000–126,500 UAH);
• a full day: about 4.8 kWh → a 5 kWh station or a wired system.

If the flat has its own gas boiler, add about 110 W: 12 hours then need more than 3.5 kWh, and it is worth comparing a station with a wired system (inverter, battery and a separate circuit for the essentials, installed by an electrician). SolarPlan's model suggests a station when about 2 kWh is enough and there is no boiler, no electric cooking and no balcony panels, and a wired system otherwise. More on the Ukraine backup power page.

How does cold affect LiFePO4 batteries?

Lithium iron phosphate (LiFePO4) batteries handle deep cycling well but are sensitive to charging below freezing. From Deye's SE-G5.1 Pro-B spec sheet:

• discharge: −20 °C to 55 °C;
• charge: 0 °C to 55 °C;
• the 5.12 kWh usable energy is measured at 25 °C, and the manufacturer notes that the current is affected by temperature and state of charge.

In practice, a battery in an unheated garage or on a balcony in winter may refuse to charge exactly when the power comes back. Keep it in a room above freezing, and check the charging temperature range of your model before you buy. The same applies to power stations.

Will solar panels help in winter?

They help, but less than people expect. We ran PVGIS, the European Commission Joint Research Centre's solar tool, for south-facing panels at 35° with 14% system losses:

Lviv's December is slightly better at 1.03 kWh a day per kW. Averages hide the spread, though. We analysed PVGIS hourly data for Kyiv from 2014 to 2023: in December and January the median day gave only 0.55 kWh per kW, and one day in four less than 0.28 kWh. Panels under snow produce almost nothing.

For a house using 6.7 kWh a day that means:

• a 10 kW array gives about 5.5 kWh on a typical winter day, most of the need but not all of it;
• on an overcast day, under 2.8 kWh;
• so over several days off-grid panels stretch the battery, while the dependable reserve comes from battery capacity or a generator.

In summer the same panels cover the essentials with plenty to spare, so their main value is lower bills in the warm season, and in winter a top-up for the battery.

Which setup fits which case?

• Flat, 4–6 hour schedules: a 1–2 kWh power station.
• Flat, 12 hours without power: a 2.5–3 kWh station or a small wired system.
• House, 12/12 schedule: a 3–5 kW hybrid inverter and 5–10 kWh of LiFePO4.
• House at risk of several days off-grid: 10 kWh plus a generator, or a larger battery; solar reduces the need for stored energy but does not remove it.

Owners of private houses can use Ukraine's state energy loan, which covers hybrid systems and generators; we explain the terms in our article on the energy loan, and the programmes are listed on the programmes page. Terms and prices change, so confirm them with the bank and the seller before you buy. Battery price trends are in the storage price index.

How to get the numbers for your own home

The figures above are for a typical set of appliances. In the free SolarPlan plan you pick your own appliances, hours and outage pattern, and the model returns three sizes (essentials, comfort and extended) with battery capacity, inverter power, a check that the battery refills between scheduled outages, and a price range. You can then receive offers from verified installers in one format. The result is a guide, not a guarantee: the installer confirms the final configuration after a site visit.