We are aware of some third party kits to convert AGAs from one fuel to another. Usually from solid fuel to either gas or oil, although there may be others on the market now too.
AGA used to make a kit that converted a genuine post 1974 oil AGA to run on '13amp electric', and that's the only one we sold. It's now discontinued and no longer available.
Conversions made by other manufacturers are a large 'grey area' as far as insurance and safety are concerned; unless the same manufacturer who made the appliance designs and makes the kit to convert it, can it be trusted to be safe and perform well?
Information on the (now discontinued) official AGA oil to 13amp Electric Conversion kit.
What could be the issues?
In short, and safety concerns aside, excessive fuel consumption and poor / unstable temperatures.
Solid fuel AGAs are made with different castings to oil or gas ones, different grades of cast-iron, different conduction plates and different positions for the heat source. This is because the heat characteristics of the solid fuel fire are different to those of a gas or oil burner, or electric element. So when the alternative heat source is fitted it consumes more fuel to do the same job and in a lot of cases doesn't ever reach the 'proper' temperature.
Conversions are normally about 20% less efficient than their 'real' AGA counterparts.
Converted AGAs often really struggle for heat in the bottom oven (simmering oven on a two oven or baking oven on a four oven).
It's also really important to ensure that flues are lined and connected properly; what's ok for one fuel is not usually the same for another and work will normally be needed to meet the required standards if an AGA is changed between fuels.
Ventilation - burners (and flues) need air, without it you're risking carbon monoxide production. It's critical to ensure the ventilation is correct for the appliance and again this can be different between fuels.
Valves / filters / tanks - oil and gas supply pipework and valves need to be correctly installed too.
AIMS FAQ page - AGA Official oil to electric conversion questions
If it's gas fired and has the gas control external to the cooker, usually mounted on its sidesheet, and has the burner feed pipes running across the front of the cooker then it is a conversion.
If it's an oil fired one and has the oil feed pipe running across the front of the cooker then this is a conversion (genuine oil AGAs do have an oil control mounted on the side but the oil feed pipe goes under the cooker's base plate and it's not visible across the front).
If it has 'plugs' (about 80mm diameter) in the middle of the hot-plates (they may look as if they'll lift out) then this is a converted solid fuel AGA.