Plug-in solar savings calculator for the Isle of Man

Kit size One panel (about 465W) Two panels (800W kit)

Most two-panel kits have about 930W of panels on an 800W inverter. Manx Utilities hasn’t yet said which figure counts towards its 800W limit, so check before you buy. See the island rules.

Where the panels go South-facing, tilted South-facing, low tilt Flat on the ground West-facing, tilted East-facing, tilted South-facing wall East-facing wall

Tilted means on an angled frame, for example in the garden or on a flat garage roof. Island sunshine data for Douglas. Peel, Ramsey and Port Erin are within about 3%.

Who is home in the daytime? Usually nobody Sometimes someone Usually someone at home

Plug-in solar only saves money on power you use as it is made. Spare power goes to the grid unpaid.

Kit price (£)

£444 is an example. Change it to the price of the kit you’re looking at, and add any delivery or electrician costs for a truer payback.

Your unit price (pence per kWh)

29.5p is Manx Utilities’ domestic unit rate from 1 April 2026. Check your bill if you’re on a different tariff.

Estimated saving each year

£111

Kit makes

940 kWh

Used at home

376 kWh

Pays back in

4.0 years

An estimate, not a promise. Real results depend on shading, weather and when you use power. Plug-in kits cannot use the Sustainable Generation tariff, so exported power earns nothing.

Worth it? Read how to choose a kit, then see how to get Manx Utilities approval.

Is plug-in solar worth it on the Isle of Man?

For a home with a sunny, south-facing spot, yes. A two-panel kit in Douglas makes about 940 kWh a year. If you use half of that at home, it saves about £139 a year and pays back a £444 kit in about 3.2 years. Even if you are out all day and use 30% of it, it saves about £83 a year and pays back the same kit in about 5.3 years.

It pays back fastest when:

• You use the power as it is made. Spare power earns nothing on the island, so running the washing machine, dishwasher and other appliances in daylight counts.
• The panels face south without shade. A south-facing wall makes about 27% less over a year than a tilted panel, but more evenly through the winter.
• The kit is well priced. The table below shows the difference between a £444 and a £749 kit.

Every kit needs Manx Utilities’ consent before it is plugged in, and our approval guide shows how to apply. If you want a bigger system that is paid for exports, plug-in or rooftop compares the two.

Month by month

What a two-panel kit makes, month by month

Douglas, south-facing. Tilted: about 940 kWh a year. On a wall: about 680 kWh, but steadier through winter.

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Tilted frame or roofSouth-facing wall

Source: EU PVGIS 5.3, 14% system losses, 930W of panels, about 2% lost to the 800W limit.

How the numbers work

• Your saving is the power you use as it is made, times your unit price. Manx Utilities charges 29.5p per kWh from 1 April 2026.
• Spare power earns nothing. A hardwired rooftop system can be paid 9.7p a unit for exports, which is the main financial difference between the two. Plug-in kits can’t use the Sustainable Generation tariff, so power sent to the grid is not paid for. This is why being at home in the daytime matters so much.
• Island sunshine is better than many people expect. A south-facing panel tilted at 35 degrees in Douglas makes about 1,034 kWh per kilowatt of panels each year. Peel, Ramsey and Port Erin are within about 3%.
• Walls make less. A south-facing wall makes about 27% less over a year than a tilted panel, though more evenly through the winter.

Typical results for a two-panel kit

Typical yearly saving and payback for a two-panel kit, by how much of its power you use at home

Used at home	Saving a year	Payback, £444 kit	Payback, £749 kit
30%	£83	5.3 years	9.0 years
40%	£111	4.0 years	6.7 years
50%	£139	3.2 years	5.4 years

Sources: sunshine yields from the European Commission’s PVGIS tool (version 5.3, 14% system losses, queried 25 September 2026). Unit price from Manx Utilities’ domestic tariffs page, read on 16 October 2026. The shares of 30%, 40% and 50% match the calculator’s three choices for who is home in the daytime, so pick the one closest to your home. For a one-panel kit the calculator uses a higher share, 50% to 70%, because a small kit’s output is more often all used. Two-panel kits lose about 2% to the 800W limit on bright days. Not included: delivery, an electrician’s check, panel ageing (output usually falls slowly each year) or future price changes. Treat results as a guide.

Related guides

• Do solar panels work in winter?
• Home batteries and solar
• Plug-in or rooftop solar?
• Is there a solar panel grant on the Isle of Man?
• Solar, heating and hot water

Common questions

Is plug-in solar worth it on the Isle of Man?

For a home with a sunny, south-facing spot, yes. A two-panel kit in Douglas saves about £83 to £139 a year, depending on how much of its power you use at home, at Manx Utilities’ 29.5p a unit.

How long does a plug-in solar kit take to pay back?

A £444 two-panel kit pays back in about 3.2 to 5.3 years, and a £749 kit in about 5.4 to 9 years, if your home uses between 50% and 30% of what it makes. The calculator on this page works it out for your own price and home.

Is it worth it if I am out at work all day?

It still saves money, more slowly. Using 30% of a two-panel kit’s power saves about £83 a year, a payback of about 5.3 years on a £444 kit. Fridges, freezers and anything on a timer use power while you are out.

Do I get paid for spare power from a plug-in kit?

No. Plug-in kits cannot use Manx Utilities’ Sustainable Generation tariff, so power sent to the grid is not paid for. A hardwired rooftop system can be paid 9.7p a unit.