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Solar Shepherd Hut Calculator

12V off-grid solar sizing for UK shepherd huts. Pick your appliances, UK location, and cloudy-day backup — get panels, battery Ah, and charge controller in seconds.

Shepherd hut usage
days
Appliances
12V off-grid solar kit for your shepherd hut
1 × 100W panel — 100W system
Daily Wh (solar-safe loads)105 Wh/day
Avg daily demand (usage-adjusted)30 Wh/day
Solar panels (100W, 12V)1 × 100W = 100W
Battery bank (12V LiFePO4)11 Ah (0.1 kWh)
MPPT charge controller20A
Location (peak sun hours)3.5 PSH/day
Estimated kit cost£845
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How to Use This Calculator

Select your usage pattern and location

Start with how often the shepherd hut is occupied — weekend use produces a much smaller average daily demand than a full-time dwelling. Location in the UK dramatically affects output: Southern England averages 3.5 peak sun hours (PSH) per day across the year; Scotland only 2.8 PSH. This is the single biggest variable in your system size.

Choose your appliances

Tick every appliance you want to run from solar. LED lights, USB charging, and a 12V mini fridge are all practical for off-grid use. The electric kettle (2000W) and fan heater (1000W) are flagged as solar-unfriendly — they're not excluded from the checklist, but they're excluded from the panel-sizing maths and trigger a gas-alternative warning. Running these from solar requires a very large and expensive battery bank for just minutes of operation.

Set battery autonomy days

In the UK, multi-day overcast periods are common — especially in Scotland, Wales, and Ireland. Set 1 autonomy day for occasional weekend visits (you'll top up before leaving), 2 days for holiday lets, and 3 days for year-round permanent use.

The Formula

Daily Wh = Sum of (Appliance Watts × Hours per Day) — kettle and heater excluded Avg Daily Wh = Daily Wh × (Days per Week ÷ 7) Panel Watts = Avg Daily Wh ÷ Peak Sun Hours ÷ 0.80 system efficiency Panels = Panel Watts ÷ 100W (round up) Battery Ah (12V) = Daily Wh × Autonomy Days ÷ (12V × 0.80 DoD) Charge Controller Amps = Total Panel Watts ÷ 12V × 1.25 safety factor

The 0.80 system efficiency factor accounts for real-world losses: battery charging losses (~5%), wiring losses (~3%), MPPT losses (~3%), temperature derating (~5%), and dirt/shading (~4%). The 1.25 charge controller safety factor is required by NEC and most UK regulations.

Example

Emma — Holiday let shepherd hut, Midlands

Emma runs a shepherd hut as a holiday let in the Midlands. Guests use it an average of 4 days per week. She wants LED lights, USB charging, and a 12V fridge, with 2 days of battery backup for cloudy weather.

UsageHoliday let (4 days/week)
LocationMidlands (3.2 PSH)
AppliancesLEDs 15W, USB 10W, Fridge 40W
Autonomy2 days

Result

Daily Wh (solar loads)~630 Wh/day
Solar panels3 × 100W = 300W
Battery bank (12V LiFePO4)~99 Ah
MPPT controller30A
Estimated kit cost~£1,100

Three 100W panels on the roof of the shepherd hut keep Emma's guests comfortable with light, charging, and a cold fridge. The wood burner handles all heating — this is the recommended approach for any UK off-grid hut. Emma chose LiFePO4 batteries for their long cycle life (3,000+ cycles) and safe chemistry indoors.

FAQ

A 2000W kettle draws 167Ah from a 12V battery every hour it runs. Boiling a kettle takes about 3 minutes — that's roughly 9Ah per boil, or 27Ah for three cups of tea. A 100Ah battery holds enough for about 11 boils before it's dead. The maths work technically, but the wire sizes (170A at 12V!) are impractical and expensive. A gas camping kettle or propane hob is the sensible off-grid solution. Gas costs pence per boil; the solar and wiring upgrade to run an electric kettle off-grid costs hundreds of pounds.
For a basic weekend shepherd hut with LED lights and USB charging: 1-2 × 100W panels. Add a 12V fridge and you need 2-3 panels. For a full-time off-grid setup: 3-4 × 100W panels. The UK's lower sun hours (2.7-3.5 PSH vs 5-6 PSH in the US) mean you need proportionally more panels for the same loads. Many shepherd hut owners use flexible monocrystalline panels screwed directly to the curved metal roof.
LiFePO4 (lithium iron phosphate) is the best choice for shepherd huts in 2024. It's safe to install indoors (no toxic offgassing), handles the UK's cold temperatures far better than other lithium chemistries, charges efficiently, and lasts 2,000-3,000+ cycles. A 100Ah 12V LiFePO4 battery costs around £300-400 and will outlast the shepherd hut warranty. Sealed lead-acid (AGM) is cheaper upfront but half the usable capacity, heavier, and shorter-lived — avoid it for new installations.
12V is standard for shepherd huts because the loads are small and the wiring runs are short. 12V LEDs, fans, USB chargers, and 12V compressor fridges are all widely available and affordable. Only move to 24V if your daily demand exceeds 1,000Wh or you have long cable runs (over 5 metres from battery to loads) — in that case 24V halves the current and reduces wire losses. For most shepherd hut builds, 12V keeps everything simple and cost-effective.
In England, Wales, and Scotland, solar panels on shepherd huts are generally permitted development — no planning permission needed — provided they don't protrude more than 200mm above the roof and aren't in a listed building or conservation area. Northern Ireland and Ireland have their own rules. Always check with your local planning authority if your site is in a National Park, AONB, or conservation area. The electrical installation itself should be carried out by a Part P registered electrician if the hut is connected to a dwelling.

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