Working through power cuts: what to prepare at the office and at home

For the manager and the administrator of a company whose accounting systems and remote desktops run on a server in Europe. You will get a list of what to prepare at the office and for staff, a way to estimate battery runtime, and a plan for a “day without power” drill.

Who this is for and why#

European data centres have redundant power and network, so power cuts in Ukraine do not affect the server. The weak points are on your side: a router without power, a provider node that went down with the building, a desktop PC with no battery. To be honest: if a person has no connection, the server cannot help them.

The demands on the workplace, though, are modest: programs and data are on the server, and a person needs a screen, a keyboard and a stable link. By Microsoft’s estimates (a single 1920×1080 monitor), working with text and spreadsheets over remote desktop needs about 100–200 kbit/s, while rich graphics and video need several megabits per second.

What you will need#

• an uninterruptible power supply (UPS) or a portable power station for the optical terminal, the router and the switch;
• a second internet link: another provider, a 4G router with a SIM card, or a satellite terminal;
• a router that can switch to the backup link automatically;
• laptops for everyone who has to work during outages;
• access to the server set up beforehand: a VPN client and a remote desktop shortcut on every laptop;
• a plug-in power meter, to measure consumption rather than guess it.

Step 1 Power for the network equipment#

Connectivity in the office depends on a chain of devices: the provider’s optical terminal (ONU), the router, the switch, the Wi-Fi access points.

1. List these devices and measure with the power meter how much they draw together.
2. Estimate the runtime: multiply the battery capacity in watt-hours (Wh) by 0.8–0.9 (conversion losses) and divide by the load in watts.
3. Check the estimate in practice: unplug the UPS or the station from the mains and time how long the equipment runs. Batteries age, so repeat the check every few months.

An example (not a standard; your figures will differ): optical terminal 6 W, router 10 W, 8-port switch 6 W, Wi-Fi access point 8 W — 30 W in total. A 300 Wh station will last roughly 300 × 0.85 / 30 ≈ 8.5 hours. An ordinary office UPS with a single 12 V 7 Ah battery is 84 Wh on paper and often about an hour in practice: the inverter takes part of the charge, and the UPS itself is designed to shut a computer down cleanly.

• If the devices are powered from 12 V or USB, a DC UPS for routers or the 12 V outputs of a station are convenient: without double conversion the charge lasts longer. Compare the voltage and polarity with the original power adapter.
• Do not plug a laser printer or a heater into this UPS, and mind the charging time: the battery has to recharge before the next outage.

Step 2 Connectivity: main and backup links#

How the provider copes with outages#

In passive optical networks (xPON) there is no equipment that needs power between the provider’s node and your optical terminal — only passive splitters. If the provider’s node has backup power and your terminal runs from a battery, the connection usually survives. Where switches are installed in buildings, each depends on the building’s power, and the connection often goes down with the electricity. This is a general observation, not a rule: ask your provider which technology you are on and how many hours its nodes hold out.

The backup link#

Automatic switching on the router#

The router checks the main link, moves traffic to the backup when the main one fails, and moves it back afterwards. It is better if it checks a host on the internet, not just the provider’s gateway: the gateway may answer even with no internet behind it.

Warning. Change routes on site, from the local network, not remotely. On MikroTik, turn on Safe Mode first (Ctrl+X in the terminal or the Safe Mode button in WinBox): if the connection to the router is lost, the changes are undone automatically (within nine minutes, per the documentation). After testing, turn the mode off the same way — the changes are kept. To roll back by hand, run /ip route remove [find comment=wan2].

A minimal example for MikroTik RouterOS 7 with static addresses: 203.0.113.1 is the main provider’s gateway, 192.168.8.1 is the 4G router (both addresses are examples).

/ip route add dst-address=0.0.0.0/0 gateway=203.0.113.1 distance=1 check-gateway=ping comment=wan1
/ip route add dst-address=0.0.0.0/0 gateway=192.168.8.1 distance=2 comment=wan2

RouterOS checks the gateway every 10 seconds and, after two failures in a row, moves to the route with the higher distance. If a static default route already exists, do not add a second one — enable check-gateway=ping on it. For a DHCP or PPPoE link the route is created by the client: its default-route-distance parameter sets the priority (the DHCP client also has check-gateway since RouterOS 7.19).

Connect the backup link to a separate port outside the local network bridge and add that port to the WAN interface list, so the default NAT and firewall rules apply to it. The example checks only the gateway; checking hosts on the internet is described in the MikroTik documentation.

After the switch the office reaches the internet from a different address — in mobile and satellite networks usually one shared by many subscribers. If access to the server is allowed only from the office address, you will not connect over the backup link. A more reliable option is a VPN in which the office initiates the connection: WireGuard carries on from the new address as soon as the client sends its first packet, and PersistentKeepalive = 25 on the office side keeps the tunnel alive behind NAT.

Step 3 Workplaces#

1. Laptops instead of desktop PCs. A laptop has its own battery and draws several times less than a desktop with a monitor. A Windows report shows the state of the battery — run this in Command Prompt:

   powercfg /batteryreport

   The command creates the file battery-report.html and shows the path to it. Compare Design Capacity and Full Charge Capacity in it: if only half of the design capacity is left, replace the battery.
2. Remote desktop from anywhere. Data and programs stay on the server, so people can work from any place with internet access. If the connection drops, the session on the server is not closed but becomes “disconnected”: after signing in again the person carries on from the same place. This advantage is easy to lose by setting too short a limit in the “Set time limit for disconnected sessions” policy (under Remote Desktop Session Host → Session Time Limits).
3. The VPN client — ahead of time. Install and test it on every laptop before the outages: doing it without power, over mobile internet and with no administrator nearby is much harder. The setup is covered in the article on WireGuard.
4. Working from home. The home router and optical terminal need power too — the calculation is the same. Outage schedules at the office and at home often differ, so agree on who works from where.
5. A phone as a hotspot. You can share its internet over Wi-Fi or a USB cable; the cable is more stable. To make Windows download only priority updates, mark that network as metered: Settings → Network & internet → Wi-Fi (Ethernet for a USB cable) → the network’s properties → Metered connection.

The response time to a server in Poland is about 15 ms from Kyiv and 15–25 ms from most Ukrainian cities (by our measurements from the networks of Ukrainian providers, October 2026; the value depends on the provider and the route). Over mobile internet it is higher and less steady: work is usually possible, but the cursor and scrolling sometimes lag. How to measure it is covered in the article on ping and mtr.

Step 4 Printing and local devices#

• Printing from a remote desktop goes to a printer connected to the user’s computer: in the RDP client this is the Local Resources tab → Printers. If there is no printer nearby or it has no power, print to PDF and print on paper later.
• USB tokens for electronic signatures, barcode scanners and similar devices reach the session through redirection and work only from the computer they are plugged into. Not every device supports this — test beforehand and decide who uses them, and from where, during an outage.
• Everything left in the office — a network printer, network storage, a local file server, the PBX — is unavailable without power to those working from home too. Move the files to the server and provide backup power for the rest.

Checklist and a “day without power” drill#

• the optical terminal, the router and the switch are powered from a UPS or a station; the runtime has been measured, not just calculated;
• the backup link is paid for, the data allowance is sufficient, switching has been tested;
• the VPN and remote desktop sign-in work on every laptop; it is known who works from the office and who from home;
• a short instruction sheet with the administrator’s and support phone numbers is printed on paper.

A list proves nothing until it is tested. Run a drill:

1. Pick an ordinary working day, not a reporting deadline, and warn people.
2. Unplug the UPS or the station from the mains so that the network equipment goes onto the battery, and note the time.
3. Disconnect the main provider’s cable and check that the router has moved to the backup link.
4. Some people work on laptop batteries in the office, some from home, one or two through a phone; everyone performs their usual operations.
5. Write down how long the equipment lasted, what did not work and how much mobile data was used. Fix what you found and repeat the drill before every winter.

How to check the result#

1. While the links are switching, run a continuous ping to the server from an office computer (203.0.113.10 is an example, use your own address; stop it with Ctrl+C):

   ping -t 203.0.113.10

   A few lost replies are normal; after that the ping should recover by itself. If a Windows server does not answer ping at all, that is the typical behaviour of its firewall: do not turn the firewall off, use the next check instead.
2. From a laptop at home or through a phone, with the VPN on, check the remote desktop port in PowerShell (10.66.0.1 is an example server address in the VPN):

   Test-NetConnection -ComputerName 10.66.0.1 -Port 3389

   The reply should contain TcpTestSucceeded : True.
3. After a deliberate break in the connection, run this on the server:

   quser

   Sessions in the Disc state mean the work is preserved and waits for the user to sign in again.

Common mistakes#

• The UPS powers the router, while the optical terminal or the switch is left in an ordinary socket.
• The SIM card of the backup link has run out of money or data.
• Access to the server is allowed only from the office address, so it does not work over the backup link or from home. The opposite mistake is opening RDP to the whole internet “for the duration of the outages”: do not do that, use a VPN.

What next#

• If accounting and files still run in the office, see how companies host them on dedicated servers and compare countries and response times.
• Close the remote desktop to outsiders: Secure RDP.
• No data centre gives absolute guarantees, so critical systems deserve a second server in another country — Standby site: three schemes and what to check.

Questions about the server go to technical support, which works around the clock: +38 044 206 08 08, info@united.net.ua.