How to size a battery and inverter to run a robot vacuum and other cleaning equipment from solar

Stop overpaying for cleaning power: how to size a battery and inverter so your robot vacuum (and other cleaning kit) runs reliably from solar

Hook: High energy bills and unpredictable peaks can make running smart, high-draw cleaning equipment a headache for small businesses. This practical 2026 tutorial walks you through real-world energy calculations — using a robot vacuum like the Dreame X50 as our anchor load — to size batteries, select an inverter, estimate charge cycles and understand cost implications for a small business solar+battery system.

The 2026 context: why this matters now

Late 2025–early 2026 continued two important trends that change the sizing calculus for small commercial solar systems:

• Battery chemistry and cost improvements: Wider adoption of LiFePO4 (LFP) cells for commercial installs has improved cycle life and safety, making deeper usable capacity (higher DoD) cost-effective for businesses.
• Smarter inverters and hybrid systems: Modern hybrid inverters now manage PV, battery and multiple AC loads more efficiently, and often include configurable export limits and smart charging to prioritise business-critical loads.

That means small businesses can realistically run intelligent cleaning fleets from a modest solar+battery bank if systems are sized correctly. Below is a step-by-step practical method you can use today — no guesswork.

Step 1 — Identify and measure the actual loads

Start with measured numbers. Manufacturer specs are useful but on-device or plug-meter measurements are more accurate because they pick up real-world behaviour (standby, peak modes, charging inefficiency).

1. Make a list of cleaning equipment you want to run from the system. Typical examples for a small business: robot vacuum (Dreame X50), dock/charging station, portable backpack vacuum, battery-powered scrubber, and possibly an upright vacuum used occasionally.
2. Measure power draw with a clamp meter or plug energy monitor. Note: robot vacuums usually draw significantly more when charging than when cruising. Record three figures where applicable: running (cleaning) watts, charging watts, and idle/standby watts.
3. Log runtime — how long each device runs daily. For example, a Dreame X50 might run 90–120 minutes per cleaning cycle; some businesses run multiple cycles per day or week depending on footfall.

If you cannot measure, use a conservative estimate range for calculations:

• Robot vacuums (modern high-suction models): 30–90 W while driving; 40–120 W while charging depending on dock and fast-charge capability.
• Commercial backpack vacuums: 500–1200 W running.
• Small floor scrubbers: 500–1500 W (depends on motor and pump).

Example assumed numbers (we’ll use these in worked examples)

• Dreame X50 cleaning draw: 60 W
• Dreame X50 charging draw (on dock): 60 W
• Daily runtime: Dreame X50 runs for 2 hours total (two 1‑hour cleans) plus charging to refill battery.
• Additional occasional 15-minute backpack vacuum use at 800 W (one session per day).

Step 2 — Calculate daily energy demand (Wh and kWh)

Use simple formulas. Keep everything in watt-hours to avoid confusion.

Formula: Energy (Wh) = Power (W) × Runtime (hours)

For our example:

• Dreame X50 cleaning: 60 W × 2 h = 120 Wh
• Dreame X50 charging overhead: in practical systems, charging energy roughly equals the cleaning energy divided by charger efficiency. Assume charger+battery charging efficiency ≈ 90% — so charging energy to replenish 120 Wh = 120 / 0.9 ≈ 133 Wh.
• Backpack vacuum: 800 W × 0.25 h = 200 Wh

Daily total (AC side before inverter losses): 120 + 133 + 200 = 453 Wh ≈ 0.45 kWh/day.

Note: this is a conservative small-business cleaning scenario. If you run multiple robots, multiple backpack vacuums or scrubbers, scale accordingly.

Step 3 — Account for system inefficiencies and safety margin

Key efficiency factors:

• Inverter efficiency: modern hybrid inverters often achieve 92–96% conversion; assume 94% (0.94).
• Battery round-trip efficiency: LiFePO4 ~90–95%; NMC ~85–90%; assume 92% (0.92) for LFP.
• Safety margin for unexpected loads & battery aging: add ~10–20% to daily energy.

Adjusted daily energy requirement (DC side):

DC energy required = AC energy / (inverter_eff × battery_eff) × safety_margin

Using our example: 0.453 kWh / (0.94 × 0.92) ≈ 0.523 kWh. With a 15% safety margin: 0.523 × 1.15 ≈ 0.60 kWh usable DC energy per day.

Step 4 — Battery sizing: usable capacity → nominal capacity

Decide your usable depth-of-discharge (DoD). In 2026 the market leader for small commercial systems is LiFePO4 because of its high cycle life and safe deep discharge. Recommended practical DoD for business use is 80% usable (keep 20% reserve for longevity).

Nominal battery capacity (kWh) = usable_daily_kWh / DoD

For our example: 0.60 kWh / 0.8 = 0.75 kWh nominal battery capacity.

Round up to stock sizes — most commercial batteries are sold in multi-kWh modules. A single 1 kWh LFP module would cover this load with headroom. However, system design should also consider autonomy (days without sun):

• 1 day autonomy: 0.75 kWh
• 3 days autonomy: 0.75 × 3 = 2.25 kWh nominal (≈ 3 kWh nominal to be conservative)

Converting to battery Ah at a chosen system voltage

Commercial systems commonly use 48 V DC. To get amp-hours:

Ah = (kWh × 1000) / Voltage

For a 1 kWh battery at 48 V: Ah = 1000 / 48 ≈ 20.8 Ah.

Step 5 — Inverter sizing: continuous power and surge

Inverter sizing must cover continuous running power and start-up surges. Motors (like backpack vacuums) and charging circuits can produce inrush current.

• Continuous rating: sum of running watts for simultaneous loads × 1.25 (safety/derating).
• Surge rating: must handle starting surges — choose an inverter with at least 2× surge capacity versus continuous rating for equipment with motors.

Example worst-case simultaneous loads in our scenario (if robot is charging and backpack vacuum runs at same time):

• Robot charging: 60 W
• Backpack vacuum: 800 W

Total running: 860 W. Apply 1.25 factor → required continuous inverter rating ≈ 1,075 VA (round up to a 1.5 kW inverter for comfort).

Surge: backpack vacuum motor may have an inrush of 2–3× running watts during start. So the inverter should have a surge rating ≈ 2,000–2,500 W. Many 1.5–2 kW inverters provide 3–5 kW surge for a few seconds — that is a good fit.

Step 6 — Solar array sizing (if you want daytime recharging and partial off-grid operation)

Calculate PV to cover daily consumption plus battery recharge and winter derating. In the UK, a conservative average is ~2.5–3.5 kWh per kWp per day across the year (higher in summer, lower in winter). For business planning, use seasonal safety factors or design for annual average and accept top-up grid or longer autonomy in winter.

PV kWp required = daily_AC_load (kWh) / average_kWh_per_kWp_per_day

Our example daily AC load was 0.453 kWh. Using 3.0 kWh/kWp/day (conservative UK average): 0.453 / 3.0 ≈ 0.15 kWp. That’s tiny. Practically, minimum installs are 1 kWp and above, so a small 1 kWp array would easily cover this load on average summer days and recharge the battery. But winter will have reduced yield, so if you want full autonomy in winter you must scale up and/or accept grid supplementation.

Rule of thumb: for business-critical cleaning that must run every day regardless of season, pair PV with a battery sized for at least 1–3 days autonomy and keep a grid connection or generator for rare extended cloudy periods.

Step 7 — Charge cycles, degradation and cost implications

Understanding cycles and lifecycle cost is crucial for ROI and maintenance planning.

• Cycle calculation: If your battery stores 1 kWh usable and your daily use is 0.6 kWh, you’re using 0.6 cycles per day (60% of capacity). Over a year that’s ≈ 219 cycles.
• Cycle life impact: LiFePO4 modules commonly achieve 3,000–6,000 cycles at 80% DoD as of 2026; that equates to 8–16 years depending on use. If you cycle 219 times/year, a 3,000‑cycle battery lasts ~13.7 years; a 6,000‑cycle battery ~27 years (calendar ageing may shorten this).
• Cost per effective kWh: A simple way to estimate is: installed battery cost (£/kWh) ÷ cycle life = cost per kWh throughput over its life. Include inverter replacement and maintenance for a full picture.

Example: if an installed battery costs £500 per kWh (installed) and is warranted for 3,000 cycles, the raw battery cost per cycle = £500 / 3,000 ≈ £0.167 per kWh of usable capacity (rough conceptual figure). Add inverter amortisation, installation, and operational costs when calculating true cost per kWh.

Step 8 — Practical installation & safety checklist

Even for a small system, follow best practice and UK rules. Key points:

• Use a certified installer for PV and battery installations — UK building regs and electrical standards must be followed.
• Install a Battery Management System (BMS) for cell balancing and safety — most LFP modules include a BMS.
• Provide proper ventilation and fire-safety clearances, especially for indoor battery rooms.
• Fit DC and AC isolators so equipment can be safely isolated for maintenance.
• Configure inverter export limits and anti-islanding settings per grid connection rules if you remain grid-tied.
• Label circuits clearly: separate circuits for critical loads (cleaning) vs general loads make prioritisation easier.

Pro tip: For business-critical cleaning operations, configure your inverter to prioritise the charging of cleaning batteries and the robot vacuum’s charging dock during daylight hours — this reduces battery cycling and grid draw.

Common scenarios and recommended system sizes

Scenario A — Minimal (robot vacuum + occasional backpack vacuum)

• Daily energy: ~0.45 kWh (example above)
• Battery: 1 kWh nominal LiFePO4 (≈0.8 kWh usable at 80% DoD) — covers daily needs with a small margin
• Inverter: 1.5 kW hybrid inverter with 3–4 kW surge
• PV: 1 kWp panel (covers most summer days; grid supplement in winter)

Scenario B — Moderate (two robot vacuums, daily backpack vacuum sessions)

• Daily energy: 1.2–1.8 kWh depending on runtimes
• Battery: 3–4 kWh nominal LiFePO4 (2.4–3.2 kWh usable at 80% DoD) for 1 day autonomy
• Inverter: 3 kW continuous with 5–7 kW surge
• PV: 1.5–3 kWp depending on desired grid independence

Scenario C — Heavy (robot fleet, scrubbers, multiple vacuums)

• Daily energy becomes multiple kWh — perform the same step-by-step sizing but expect battery banks of 5–15 kWh or more and inverters 5 kW+ depending on simultaneous loads.

Maintenance, monitoring and lifecycle management

Plan for monitoring and scheduled maintenance:

• Install a monitoring system that tracks charge/discharge cycles, depth of discharge, and inverter events. Many hybrid inverters provide cloud dashboards that record cycles and state-of-health.
• Set alerts for abnormal charging behaviour, high temperatures or repeated deep discharge events.
• Schedule annual checks for wiring integrity, BMS updates and inverter firmware updates — firmware improvements in 2025–26 have added efficiency optimisations worth applying.

Off-grid operation: realities for small businesses

Complete off-grid operation for cleaning loads is possible but requires conservative sizing for winter and cloudy periods and possibly a generator or grid backup for rare long stretches. Hybrid systems that remain grid-connected but prioritise solar and battery first are often the most cost-effective and low-risk option for small businesses.

Quick reference formulas (save this block)

• Energy (Wh) = Power (W) × Time (h)
• DC required (kWh) = AC load (kWh) / (inverter_eff × battery_eff)
• Battery nominal (kWh) = usable_daily_kWh / DoD
• Battery Ah @ V = (kWh × 1000) / V
• Inverter continuous ≈ sum(running_W) × 1.25
• Required inverter surge ≈ 2–3 × largest motor start watt
• PV kWp ≈ daily_AC_kWh / average_kWh_generated_per_kWp_per_day

Checklist before purchasing

1. Measure actual device power draw and run times with a plug meter.
2. Decide desired autonomy (days off-grid) and acceptable DOD.
3. Pick battery chemistry (LiFePO4 recommended for small commercial installs in 2026) and size accordingly.
4. Choose an inverter with adequate continuous and surge ratings and hybrid capabilities for PV+Batt+Grid.
5. Factor in inefficiencies (inverter + battery) and a 10–20% safety margin.
6. Plan for monitoring, maintenance and replacement schedule — include warranties and expected cycle life in ROI calculations.

Final considerations and future-proofing

Design systems with modular expansion in mind. In 2026 it's common to install a modest battery and later add extra modules as needs grow or as more cleaning robots are added. Hybrid inverters that can manage more battery capacity or parallel inverter architectures simplify upgrades.

Also watch for software features that improve management: schedules that charge robots during PV generation windows, firmware that reduces battery stress, and API integration so your building management system can prioritise critical cleaning operations.

Conclusion — actionable next steps

Sizing a battery and inverter for robot vacuums and cleaning equipment is straightforward when you measure actual loads and follow conservative efficiency assumptions. For a small-business scenario anchored by a Dreame X50-style robot, many operations will be satisfied with a 1–4 kWh LiFePO4 battery and a 1.5–3 kW hybrid inverter — scaled up as more equipment or autonomy is needed.

Ready to move from planning to action? Get three site-specific quotes from certified installers, include a measurement session for actual device draws, and request a written sizing summary that shows assumptions (efficiency, DoD, autonomy). That document will be invaluable to compare suppliers and verify ROI.

Call to action

Want a vetted supplier to size your system and provide a tailored quote? Visit powersuppliers.uk to compare certified installers, request a site survey and download our free calculator template to plug in your exact device measurements. Make your cleaning operations greener and cheaper — starting today.

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